It seems that there are only very few cases where that is useful, and
for now we prefer not having that check. This means that we might
perform some unnecessary checks, but that should be rare and not
performance critical.
Instead of sending NULL's over a network, we now convert the subqueries
in the form of:
SELECT t.a, NULL, NULL FROM (SELECT a FROM table)t;
And we recursively plan the inner part so that we don't send the NULL's
over network. We still need the NULLs in the outer subquery because we
currently don't have an easy way of updating all the necessary places in
the query.
Add some documentation for how the conversion is done
Baseinfo also has pushed down filters etc, so it makes more sense to use
BaseRestrictInfo to determine what columns have constant equality
filters.
Also RteIdentity is used for removing conversion candidates instead of
rteIndex.
It seems that most of the updates were broken, we weren't aware of it
because there wasn't any data in the tables. They are broken mostly
because local tables do not have a shard id and some code paths should
be updated with that information, currently when there is an invalid
shard id, it is assumed to be pruned.
Consider local tables in router planner
In case there is a local table, the shard id will not be valid and there
are some checks that rely on shard id, we should skip these in case of
local tables, which is handled with a dummy placement.
Add citus local table dist table join tests
add local-dist table mixed joins tests
AllDataLocallyAccessible and ContainsLocalTableSubqueryJoin are removed.
We can possibly remove ModifiesLocalTableWithRemoteCitusLocalTable as
well. Though this removal has a side effect that now when all the data
is locally available, we could still wrap a relation into a subquery, I
guess that should be resolved in the router planner itself.
Add more tests
When we wrap an RTE to subquery we are updating the variables varno's as
1, however we should also update the varno's of vars in quals.
Also some other small code quality improvements are done.
The previous algorithm was not consistent and it could convert different
RTEs based on the table orders in the query. Now we convert local tables
if there is a distributed table which doesn't have a unique index. So if
there are 4 tables, local1, local2, dist1, dist2_with_pkey then we will
convert local1 and local2 in `auto` mode. Converting a distributed table
is not that logical because as there is a distributed table without a
unique index, we will need to convert the local tables anyway. So
converting the distributed table with pkey is redundant.
Remove FillLocalAndDistributedRTECandidates and use
ShouldConvertLocalTableJoinsToSubqueries, which simplifies things as we
rely on a single function to decide whether we should continue
converting RTE to subquery.
We should not recursively plan an already routable plannable query. An
example of this is (SELECT * FROM local JOIN (SELECT * FROM dist) d1
USING(a));
So we let the recursive planner do all of its work and at the end we
convert the final query to to handle unsupported joins. While doing each
conversion, we check if it is router plannable, if so we stop.
Only consider range table entries that are in jointree
If a range table is not in jointree then there is no point in
considering that because we are trying to convert range table entries to
subqueries for join use case.
Check equality in quals
We want to recursively plan distributed tables only if they have an
equality filter on a unique column. So '>' and '<' operators will not
trigger recursive planning of distributed tables in local-distributed
table joins.
Recursively plan distributed table only if the filter is constant
If the filter is not a constant then the join might return multiple rows
and there is a chance that the distributed table will return huge data.
Hence if the filter is not constant we choose to recursively plan the
local table.
When doing local-distributed table joins we convert one of them to
subquery. The current policy is that we convert distributed tables to
subquery if it has a unique index on a column that has unique
index(primary key also has a unique index).
The logical planner cannot handle joins between local and distributed table.
Instead, we can recursively plan one side of the join and let the logical
planner handle the rest.
Our algorithm is a little smart, trying not to recursively plan distributed
tables, but favors local tables.
A utility function is added so that each caller can implement a handler
for each index on a given table. This means that the caller doesn't need
to worry about how to access each index, the only thing that it needs to
do each to implement a function to which each index on the table is
passed iteratively.
When Citus needs to parallelize queries on the local node (e.g., the node
executing the distributed query and the shards are the same), we need to
be mindful about the connection management. The reason is that the client
backends that are running distributed queries are competing with the client
backends that Citus initiates to parallelize the queries in order to get
a slot on the max_connections.
In that regard, we implemented a "failover" mechanism where if the distributed
queries cannot get a connection, the execution failovers the tasks to the local
execution.
The failover logic is follows:
- As the connection manager if it is OK to get a connection
- If yes, we are good.
- If no, we fail the workerPool and the failure triggers
the failover of the tasks to local execution queue
The decision of getting a connection is follows:
/*
* For local nodes, solely relying on citus.max_shared_pool_size or
* max_connections might not be sufficient. The former gives us
* a preview of the future (e.g., we let the new connections to establish,
* but they are not established yet). The latter gives us the close to
* precise view of the past (e.g., the active number of client backends).
*
* Overall, we want to limit both of the metrics. The former limit typically
* kics in under regular loads, where the load of the database increases in
* a reasonable pace. The latter limit typically kicks in when the database
* is issued lots of concurrent sessions at the same time, such as benchmarks.
*/
When distributing a columnar table, as well as changing options on a distributed columnar table, this patch will forward the settings from the coordinator to the workers.
For propagating options changes on an already distributed table this change is pretty straight forward. Before applying the change in options locally we will create a `DDLJob` that contains a call to `alter_columnar_table_set(...)` for every shard placement with all settings of the current table. This goes both for setting an option as well as resetting. This will reset the values to the defaults configured on the coordinator. Having the effect that the coordinator is authoritative on the settings and makes sure the shards have the same settings set as the table on the coordinator.
When a columnar table is distributed it is using the `TableDDLCommand` infra structure to create a new kind of `TableDDLCommand`. This new type, called a `TableDDLCommandFunction` contains a context and 2 function pointers to execute. One function returns the command as applied on the table, the second function will return the sql command to apply to a shard with a given shard id. The schema name is ignored as it will use the fully qualified name of the shard in the same schema as the base table.
Multi-row execution already uses sequential execution. When shards
are local, using local execution is profitable as it avoids
an extra connection establishment to the local node.
If MemoryContextAlloc errors out -e.g. during an OOM-, ConnectionHashEntry->connections
stays as NULL.
With this commit, we add isValid flag to ConnectionHashEntry that should be set to true
right after we allocate & initialize ConnectionHashEntry->connections list properly, and we
check it before accesing to ConnectionHashEntry->connections.
The name of the function is different than the implemantation. Because
the function is designed to only consider SELECT queries. Also this
changes the assert with an error.
Refactor internals on how Citus creates the SQL commands it sends to recreate shards.
Before Citus collected solely ddl commands as `char *`'s to recreate a table. If they were used to create a shard they were wrapped with `worker_apply_shard_ddl_command` and send to the workers. On the workers the UDF wrapping the ddl command would rewrite the parsetree to replace tables names with their shard name equivalent.
This worked well, but poses an issue when adding columnar. Due to limitations in Postgres on creating custom options on table access methods we need to fall back on a UDF to set columnar specific options. Now, to recreate the table, we can not longer rely on having solely DDL statements to recreate a table.
A prototype was made to run this UDF wrapped in `worker_apply_shard_ddl_command`. This became pretty messy, hard to understand and subsequently hard to maintain.
This PR proposes a refactor of the internal representation of table ddl commands into a `TableDDLCommand` structure. The current implementation only supports a `char *` as its contents. Based on the use of the DDL statement (eg. creating the table -mx- or creating a shard) one of two different functions can be called to get the statement to send to the worker:
- `GetTableDDLCommand(TableDDLCommand *command)`: This function returns that ddl command to create the table. In this implementation it will just return the `char *`. This has the same functionality as getting the old list and not wrapping it.
- `GetShardedTableDDLCommand(TableDDLCommand *command, uint64 shardId, char *schemaName)`: This function returns the ddl command wrapped in `worker_apply_shard_ddl_command` with the `shardId` as an argument. Due to backwards compatibility it also accepts a. `schemaName`. The exact purpose is not directly clear. Ideally new implementations would work with fully qualified statements and ignore the `schemaName`.
A future implementation could accept 2.function pointers and a `void *` for context to let the two pointers work on. This gives greater flexibility in controlling what commands get send in which situations. Also, in a future, we could implement the intermediate step of creating the `parsetree` datastructure of statements based on the contents in the catalog with a corresponding deparser. For sharded queries a mutator could be ran over the parsetree to rewrite the tablenames to the names with the shard identifier. This will completely omit the requirement for `worker_apply_shard_ddl_command`.
Considering the adaptive connection management
improvements that we plan to roll soon, it makes it
very helpful to know the number of active client
backends.
We are doing this addition to simplify yhe adaptive connection
management for single node Citus. In single node Citus, both the
client backends and Citus parallel queries would compete to get
slots on Postgres' `max_connections` on the same Citus database.
With adaptive connection management, we have the counters for
Citus parallel queries. That helps us to adaptively decide
on the remote executions pool size (e.g., throttle connections
if necessary).
However, we do not have any counters for the total number of
client backends on the database. For single node Citus, we
should consider all the client backends, not only the remote
connections that Citus does.
Of course Postgres internally knows how many client
backends are active. However, to get that number Postgres
iterates over all the backends. For examaple, see [pg_stat_get_db_numbackends](8e90ec5580/src/backend/utils/adt/pgstatfuncs.c (L1240))
where Postgres iterates over all the backends.
For our purpuses, we need this information on every connection
establishment. That's why we cannot affort to do this kind of
iterattion.
CitusTableTypeIdList() function iterates on all the entries of pg_dist_partition
and loads all the metadata in to the cache. This can be quite memory intensive
especially when there are lots of distributed tables.
When partitioned tables are used, it is common to have many distributed tables
given that each partition also becomes a distributed table.
CitusTableTypeIdList() is used on every CREATE TABLE .. PARTITION OF.. command
as well. It means that, anytime a partition is created, Citus loads all the
metadata to the cache. Note that Citus typically only loads the accessed table's
metadata to the cache.
* Move local execution after the remote execution
Before this commit, when both local and remote tasks
exist, the executor was starting the execution with
local execution. There is no strict requirements on
this.
Especially considering the adaptive connection management
improvements that we plan to roll soon, moving the local
execution after to the remote execution makes more sense.
The adaptive connection management for single node Citus
would look roughly as follows:
- Try to connect back to the coordinator for running
parallel queries.
- If succeeds, go on and execute tasks in parallel
- If fails, fallback to the local execution
So, we'll use local execution as a fallback mechanism. And,
moving it after to the remote execution allows us to implement
such further scenarios.
The adaptive executor emulates the TCP's slow start algorithm.
Whenever the executor needs new connections, it doubles the number
of connections established in the previous iteration.
This approach is powerful. When the remote queries are very short
(like index lookup with < 1ms), even a single connection is sufficent
most of the time. When the remote queries are long, the executor
can quickly establish necessary number of connections.
One missing piece on our implementation seems that the executor
keeps doubling the number of connections even if the previous
connection attempts have been finalized. Instead, we should
wait until all the attempts are finalized. This is how TCP's
slow-start works. Plus, it decreases the unnecessary pressure
on the remote nodes.
Before this commit, we let AdaptiveExecutorPreExecutorRun()
to be effective multiple times on every FETCH on cursors.
That does not affect the correctness of the query results,
but adds significant overhead.
It seems that we forgot to pass the revelant
flag to enable Postgres' parallel query
capabilities on the shards when user does
EXPLAIN ANALYZE on a distributed table.
If one wishes to iterate through a List and insert list elements in
PG13, it is not safe to use for_each_ptr as the List representation
in PostgreSQL no longer linked lists, but arrays, and it is possible
that the whole array is repalloc'ed if ther is not sufficient space
available.
See postgres commit 1cff1b95ab6ddae32faa3efe0d95a820dbfdc164 for more
information
When a relation is used on an OUTER JOIN with FALSE filters,
set_rel_pathlist_hook may not be called for the table.
There might be other cases as well, so do not rely on the hook
for classification of the tables.
RemoveDuplicateJoinRestrictions() function was introduced with the aim of decrasing the overall planning times by eliminating the duplicate JOIN restriction entries (#1989). However, it turns out that the function itself is so CPU intensive with a very high algorithmic complexity, it hurts a lot more than it helps. The function is a clear example of premature optimization.
The table below shows the difference clearly:
"distributed query planning
time master" RemoveDuplicateJoinRestrictions() execution time on master "Remove the function RemoveDuplicateJoinRestrictions()
this PR"
5 table INNER JOIN 9 msec 2msec 7 msec
10 table INNER JOIN 227 msec 194 msec 29 msec
20 table INNER JOIN 1 sec 235 msec 1 sec 139 msec 90 msecs
50 table INNER JOIN 24 seconds 21 seconds 1.5 seconds
100 table INNER JOIN 2 minutes 16 secods 1 minute 53 seconds 23 seconds
250 table INNER JOIN Bottleneck on JoinClauseList 18 minutes 52 seconds Bottleneck on JoinClauseList
5 table INNER JOIN in subquery 9 msec 0 msec 6 msec
10 table INNER JOIN subquery 33 msec 10 msec 32 msec
20 table INNER JOIN subquery 132 msec 67 msec 123 msec
50 table INNER JOIN subquery 1.2 seconds 900 msec 500 msec
100 table INNER JOIN subquery 6 seconds 5 seconds 2 seconds
250 table INNER JOIN subquery 54 seconds 37 seconds 20 seconds
5 table LEFT JOIN 5 msec 0 msec 5 msec
10 table LEFT JOIN 11 msec 0 msec 13 msec
20 table LEFT JOIN 26 msec 2 msec 30 msec
50 table LEFT JOIN 150 msec 15 msec 193 msec
100 table LEFT JOIN 757 msec 71 msec 722 msec
250 table LEFT JOIN 8 seconds 600 msec 8 seconds
5 JOINs among 2 table JOINs 37 msec 11 msec 25 msec
10 JOINs among 2 table JOINs 536 msec 306 msec 352 msec
20 JOINs among 2 table JOINs 794 msec 181 msec 640 msec
50 JOINs among 2 table JOINs 25 seconds 2 seconds 22 seconds
100 JOINs among 2 table JOINs Bottleneck on JoinClauseList 9 seconds Bottleneck on JoinClauseList
150 JOINs among 2 table JOINs Bottleneck on JoinClauseList 46 seconds Bottleneck on JoinClauseList
On top of the performance penalty, the function had a critical bug #4255, and with #4254 we hit one more important bug. It should be fixed by adding the followig check to the ContextCoversJoinRestriction():
```
static bool
JoinRelIdsSame(JoinRestriction *leftRestriction, JoinRestriction *rightRestriction)
{
Relids leftInnerRelIds = leftRestriction->innerrel->relids;
Relids rightInnerRelIds = rightRestriction->innerrel->relids;
if (!bms_equal(leftInnerRelIds, rightInnerRelIds))
{
return false;
}
Relids leftOuterRelIds = leftRestriction->outerrel->relids;
Relids rightOuterRelIds = rightRestriction->outerrel->relids;
if (!bms_equal(leftOuterRelIds, rightOuterRelIds))
{
return false;
}
return true;
}
```
However, adding this eliminates all the benefits tha RemoveDuplicateJoinRestrictions() brings.
I've used the commands here to generate the JOINs mentioned in the PR: https://gist.github.com/onderkalaci/fe8654f9df5916c7af4c7c5eb892561e#file-gistfile1-txt
Inner and outer JOINs behave roughly the same, to simplify the table only added INNER joins.
* Fix incorrect join related fields
Ruleutils expect to give the original index of join columns hence we
should consider the dropped columns while setting the fields in
SetJoinRelatedFieldsCompat.
* add some more tests for joins
* Move tests to join.sql and create a utility function
Disallow `ON TRUE` outer joins with reference & distributed tables
when reference table is outer relation by fixing the logic bug made
when calling `LeftListIsSubset` function.
Also, be more defensive when removing duplicate join restrictions
when join clause is empty for non-inner joins as they might still
contain useful information for non-inner joins.
It seems like Postgres could call set_rel_pathlist() for
the same relation multiple times. This breaks the logic
where we assume relationCount eqauls to the number of
entries in relationRestrictionList.
In summary, relationRestrictionList may contain duplicate
entries.
With this commit, we make sure that local execution adds the
intermediate result size as the distributed execution adds. Plus,
it enforces the citus.max_intermediate_result_size value.
We should not access CurrentLocalExecutionStatus directly because that
would mean that we could also set it directly, which we shouldn't
because we have checks to see if the new state is possible, otherwise we
error.
Before this commit, the logic was:
- As long as the outer side of the JOIN is not a JOIN (e.g., relation
or subquery etc.), we check for the existence of any recurring
tuples. There were two implications of this decision.
First, even if a subquery which is on the outer side contains
distributed table JOIN reference table, Citus would unnecessarily throw
an error. Note that, the JOIN inside the subquery would already
be going to be tested recursively. But, as long as that check
passes, there is no reason for the upper JOIN to fail. An example, which
used to fail and now works:
SELECT * FROM (SELECT * FROM dist JOIN ref) as foo LEFT JOIN dist;
Second, certain JOINs, especially with ON (true) conditions were not
represented as Citus expects the JOINs to be in the format
DeferredErrorIfUnsupportedRecurringTuplesJoin().
Use short lived per-tuple context in citus_evaluate_expr like
(pg) evaluate_expr does.
We should not use planState->ExprContext when evaluating expressions
as it might lead to freeing the same executor twice (first one happens
in citus_evaluate_expr itself and the other one happens when postgres
doing clean-up for the top level executor state), which in turn might
cause seg.faults.
However, now as we don't have necessary planState info to evaluate
prepared statements, we also add planState->es_param_list_info to
per-tuple ExprContext.
With postgres 13, there is a global lock that prevents multiple VACUUMs
happening in the current database. This global lock is taken for a short
time but this creates a problem because of the following:
- We execute the VACUUM for the shell table through the standard process
utility. In this step the global lock is taken for the current database.
- If the current node has shard placements then it tries to execute
VACUUM over a connection to localhost with ExecuteUtilityTaskList.
- the VACUUM on shard placements cannot proceed because it is waiting
for the global lock for the current database to be released.
- The acquired lock from the VACUUM for shell table will not be released
until the transaction is committed.
- So there is a deadlock.
As a solution, we commit the current transaction in case of VACUUM after
the VACUUM is executed for the shell table. Executing the VACUUM on a
shell table is not important because the data there will probably be
truncated. PostprocessVacuumStmt takes the necessary locks on the shell
table so we don't need to take any extra locks after we commit the
current transaction.
The prepare for upgrade script creates the `'public.pg_dist_rebalance_strategy` table which is not dropped when the upgrade is finished. This may block future upgrades.
Multi-row & router INSERT's were crashing with local execution if at
least one of the DEFAULT columns were not specified in VALUES list.
This was because, the changes we make on query->values_lists and
query->targetList was sufficient for deparsing given INSERT for remote
execution but not sufficient for local execution.
With this commit, DEFAULT value normalization for multi-row & router
INSERT's is fixed by adding dummy column references for unspecified
DEFAULT columns.
Citus has the logic to truncate the long shard names to prevent
various issues, including self-deadlocks. However, for partitioned
tables, when index is created on the parent table, the index names
on the partitions are auto-generated by Postgres. We use the same
Postgres function to generate the index names on the shards of the
partitions. If the length exceeds the limit, we switch to sequential
execution mode.
In postmasters execution of _PG_init, IsUnderPostmaster will be false and
we want to do the cleanup at that time only, otherwise there is a chance that
there will be parallel queries and we might do a cleanup for things that are
already in use.
After the connection timeout, we fail the session/pool. However, the
underlying connection can still be trying to connect. That is dangerous
because the new placement executions have already been in place. The
executor cannot handle the situation where multiple of
EXECUTION_ORDER_ANY task executions succeeds.
Adding a regression test doesn't seem easily doable. To reproduce the issue
- Add 2 worker nodes
- create a reference table
- set citus.node_connection_timeout to 1ms (requires code change)
- Continiously execute `SELECT count(*) FROM ref_table`
- Sometime later, you hit an out-of-array access in
`ScheduleNextPlacementExecution()` hence crashing.
- The reason for that is sometimes the first connection
successfully established while the executor is already
trying to execute the query on the second node.
We currently do not support volatile functions in update/delete statements
because the function evaluation logic does not know how to distinguish
volatile functions (that need to be evaluated per row) from stable functions
(that need to be evaluated per query), and it is also not safe to push the
volatile functions down on replicated tables.
Add sort method parameter for regression tests
Fix check-style
Change sorting method parameters to enum
Polish
Add task fields to OutTask
Add test into multi_explain
Fix isolation test
As the previous versions of Citus don't know how to handle citus local
tables, we should prevent downgrading from 9.5 to older versions if any
citus local tables exists.
Pushing down the CALLs to the node that the CALL is executed is
dangerous and could lead to infinite recursion.
When the coordinator added as worker, Citus was by chance preventing
this. The coordinator was marked as "not metadatasynced" node
in pg_dist_node, which prevented CALL/function delegation to happen.
With this commit, we do the following:
- Fix metadatasynced column for the coordinator on pg_dist_node
- Prevent pushdown of function/procedure to the same node that
the function/procedure is being executed. Today, we do not sync
pg_dist_object (e.g., distributed functions metadata) to the
worker nodes. But, even if we do it now, the function call delegation
would prevent the infinite recursion.
* Not take ShareUpdateExlusiveLock on pg_dist_transaction
We were taking ShareUpdateExlusiveLock on pg_dist_transaction during
recovery to prevent multiple recoveries happening concurrenly. VACUUM(
not FULL) also takes ShareUpdateExclusiveLock, and they can conflict. It
seems that VACUUM will skip the table if there is a conflicting lock
already taken unless it is doing the vacuum to prevent id wraparound, in
which case there can be a deadlock. I guess the deadlock happens if:
- VACUUM takes a lock on pg_dist_transaction and is done for id
wraparound problem
- The transaction in the maintenance tries to take a lock but
cannot as that conflicts with the lock acquired by VACUUM
- The transaction in the maintenance daemon has a very old xid hence
VACUUM cannot proceed.
If we take a row exclusive lock in transaction recovery then it wouldn't
conflict with VACUUM hence it could proceed so the deadlock would be
resolved. To prevent concurrent transaction recoveries happening, an
advisory lock is taken with ShareUpdateExlusiveLock as before.
* Use CITUS_OPERATIONS tag
* Not allow removing a single node with ref tables
We should not allow removing a node if it is the only node in the
cluster and there is a data on it. We have this check for distributed
tables but we didn't have it for reference tables.
* Update src/test/regress/expected/single_node.out
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
* Update src/test/regress/sql/single_node.sql
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
This commit brings following features:
Foreign key support from citus local tables to reference tables
* Foreign key support from reference tables to citus local tables
(only with RESTRICT & NO ACTION behavior)
* ALTER TABLE ENABLE/DISABLE trigger command support
* CREATE/DROP/ALTER trigger command support
and disallows:
* ALTER TABLE ATTACH/DETACH PARTITION commands
* CREATE TABLE <postgres table> ATTACH PARTITION <citus local table>
commands
* Foreign keys from postgres tables to citus local tables
(the other way was already disallowed)
for citus local tables.
Introduce table entry utility functions
Citus table cache entry utilities are introduced so that we can easily
extend existing functionality with minimum changes, specifically changes
to these functions. For example IsNonDistributedTableCacheEntry can be
extended for citus local tables without the need to scan the whole
codebase and update each relevant part.
* Introduce utility functions to find the type of tables
A table type can be a reference table, a hash/range/append distributed
table. Utility methods are created so that we don't have to worry about
how a table is considered as a reference table etc. This also makes it
easy to extend the table types.
* Add IsCitusTableType utilities
* Rename IsCacheEntryCitusTableType -> IsCitusTableTypeCacheEntry
* Change citus table types in some checks
create_distributed_function(function_name,
distribution_arg_name,
colocate_with text)
This UDF did not allow colocate_with parameters when there were no
disttribution_arg_name supplied. This commit changes the behaviour to
allow missing distribution_arg_name parameters when the function should
be colocated with a reference table.
* Hide citus.subquery_pushdown flag
This flag is dangerous and could likely to let queries
return wrong results.
The flag has a very specific purpose for a very specific
data distribution and query structure. In those cases, when
the flag is set, the user can skip recursive planning altogether
*at their own risk*.
The meaning of the flag is that "I know what I'm doing such that
the query structure/data distribution is on my control, so Citus
can skip many correctness checks".
For regular users, enabling this flag is discouraged. We have to
keep the support only for backward compatibility for some users.
In addition to that, give a NOTICE to discourage new users to
use it.
RemoveCoordinatorPlacement does not do what it says. It removes the
coordinator placement only if there are other placements, so it is not a
single node, and only if the coordinator has a placement.
AllTargetExpressionsAreColumnReferences would return false if a query
had an entry that is referencing the outer query. It seems safe to not
have this for non-distributed tables, such as reference tables. We
already have separate checks for other cases such as having limits.
FindNodeCheck is not clear about what the function is doing. They are
renamed to FindNodeMatchingCheckFunctionXXX. Also for choosing elements in these
functions, CheckNodeFunc type is introduced.
It seems that currently we process even postgres tables in explain
commands. This is because we register a hook for explain and we don't
have any check to see if the query has any citus table.
With this commit, we now send the buffer usage as well to the relevant
API. There is some duplicate in the code but it is because of the
existing structure, we can refactor this separately.
The codebase is updated to use varattnosync and varnosyn and we defined
the macros for older versions. This way we can just remove the macros
when we drop an older version.
CMDTAG_SELECT exists in PG12 hence defining a MACRO such as
CMDTAG_SELECT -> "SELECT" is not possible. I chose CMDTAG_SELECT_COMPAT
because with the COMPAT suffix it is explicit that it maps to different
things in different versions and also has a less chance of mapping
something irrevelant. For example if we used SELECT as a macro, then it
would map every SELECT to whatever it is mapping to, which might have
unexpected/undesired behaviour.
The error message when index has opclassopts is improved and the commit
from postgres side is also included for future reference.
Also some minor style related changes are applied.
Error out if index has opclassopts.
Changelog entry on PG13:
Allow CREATE INDEX to specify the GiST signature length and maximum number of integer ranges (Nikita Glukhov)
Postgres 13 added a new VACUUM option, PARALLEL. It is now supported
in our code as well.
Relevant changelog message on postgres:
Allow VACUUM to process indexes in parallel (Masahiko Sawada, Amit Kapila)
This commit mostly adds pg_get_triggerdef_command to our ruleutils_13.
This doesn't add anything extra for ruleutils 13 so it is basically a copy
of the change on ruleutils_12
When there is a join alias, var->varnosync will point to the alias and
var->varno will point to the table itself, but we need to use the alias
when deparsing the query. Hence a workaround is introduced to solve this
problem in ruleutils. Normally this case can be understood with
dpns->plan == NULL check but in our case, dpns->plan is always NULL. We
should sync our ruleutils at some point with postgres ruleutils. This
could be a wrong solution as well but the tests pass.
Rte index is increased by range table index offset in pg >= 13. The
offset is removed with the pg >= 13.
Currently pushdown for union all is disabled because translatedVars is
set to nil on postgres side, and we were using translatedVars to
figure out if partition key has the same index in both sides of union
all. This should be fixed.
Commit on postgres side:
6ef77cf46e81f45716ec981cb08781d426181378
fix union all pushdown logic for pg13
Before pg 13, there was a field, translatedVars, and we were using that
to understand if the partition key has the same index on both sides of
the union all. With pg13 there is a parent_colnos field in appendRelInfo
and we can use that to get the attribute numbers(varattnos) in union all
vars. We make use of parent_colnos instead of translatedVars in pg >=13.
For joins 3 new fields are added, joinleftcols, joinrightcols, and
joinmergedcols. We are not interested in joinmergedcols because we
always expand the column used in joins. There joinmergedcols is always 0
in our case.
For filling joinleftcols and joinrightcols we basically construct the
lists with sequences so either list is of the form: [1 2 3 4 .... n]
Ruleutils is not completed synced with postgres ruleutils and the most
important part is identify_join_columns function change, which now uses
joinleftcols and joinrightcols.
Commit on postgres side:
9ce77d75c5ab094637cc4a446296dc3be6e3c221
A useful email thread:
https://www.postgresql.org/message-id/flat/7115.1577986646%40sss.pgh.pa.us#0ae1d66feeb400013fbaa67a7cccd6ca
PG13 uses joinmergedcols, joinleftcols and joinrightcols for finding
join order now. There relevant fields are set on citus side.
Postgres side commit:
9ce77d75c5ab094637cc4a446296dc3be6e3c221
Postgres changed some join related fields and therefore they also
changed ruleutils, this commit applies those changes to our copy of
ruleutils.
Related commit on postgres side:
9ce77d75c5ab094637cc4a446296dc3be6e3c221
Postgres introduced QueryCompletion struct. Hence a compat utility is
added to finish query completion for older versions and pg >= 13.
The commit on Postgres side:
2f9661311b83dc481fc19f6e3bda015392010a40
addRangeTableEntryXXX methods return a ParseNamespaceItem with pg >= 13.
RangeTableEntryFromNSItem macro is added so that we return the range
table entry from the ParseNamespaceItem in pg>=13 and for pg < 13 rte
would already be returned with addRangeTableEntryXXX methods.
Commit on Postgres side:
5815696bc66b3092f6361f53e0394909647042c8
Since PG13 changed the list, a listcell doesn't contain data anymore.
Therefore Set_ptr_value macro is created, so that depending on the
version it will either use cell->data.ptr_value or cell->ptr_value.
Commit on Postgres side:
1cff1b95ab6ddae32faa3efe0d95a820dbfdc164
Since ExplainOnePlan expects BufferUsage as well with PG >= 13,
ExplainOnePlanCompat is added.
Commit on Postgres side:
ed7a5095716ee498ecc406e1b8d5ab92c7662d10
Commit on postgres side:
05d8449e73694585b59f8b03aaa087f04cc4679a
Command on postgres side:
git log --all --grep="hashutils"
include common/hashfn.h for pg >= 13
tag_hash was moved from hsearch.h to hashutils.h then to hashfn.h
Commits on Postgres side:
9341c783cc42ffae5860c86bdc713bd47d734ffd
PortalDefineQuery doesn't accept char* for command tag anymore with PG
>= 13. We are currently only using it with Select, therefore a Portal
define query compat for select is created.
Commit on PG side:
2f9661311b83dc481fc19f6e3bda015392010a40
As the new planner and pg_plan_query_compat methods expect the query
string as well, macros are defined to be compatible in different
versions of postgres.
Relevant commit on Postgres:
6aba63ef3e606db71beb596210dd95fa73c44ce2
Command on Postgres:
git log --all --grep="pg_plan_query"
With PG13 heap_* (heap_open, heap_close etc) are replaced with table_*
(table_open, table_close etc).
It is better to use the new table access methods in the codebase and
define the macros for the previous versions as we can easily remove the
macro without having to change the codebase when we drop the support for
the old version.
Commits that introduced this change on Postgres:
f25968c49697db673f6cd2a07b3f7626779f1827
e0c4ec07284db817e1f8d9adfb3fffc952252db0
4b21acf522d751ba5b6679df391d5121b6c4a35f
Command to see relevant commits on Postgres side:
git log --all --grep="heap_open"
Pass the list to lnext API
lnext API now expects the list as well.
The commit on Postgres that introduced the change: 1cff1b95ab6ddae32faa3efe0d95a820dbfdc164
lnext_compat and list_delete_cell_compat macros are introduced so that
we can use these macros in the codebase without having to use #if
directives in the codebase.
Related commit on postgres:
1cff1b95ab6ddae32faa3efe0d95a820dbfdc164
Command to search in postgres:
git log --all --grep="list_delete_cell"
add ListCellAndListWrapper
When iterating a list in separate function calls, we need both the list
and the current cell starting from PG13, therefore
ListCellAndListWrapper is added to store both as a wrapper.
Use ListCellAndListWrapper in foreign key test udfs
As we iterate a list in these udfs using a functionContext, we need to
use the wrapper to be able to access both the list and the current cell.
With this patch, we introduce `locally_reserved_shared_connections.c/h` files
which are responsible for reserving some space in shared memory counters
upfront.
We sometimes need to reserve connections, but not necessarily
establish them. For example:
- COPY command should reserve connections as it cannot know which
connections it needs in which order. COPY establishes connections
as any input data hits the workers. For example, for router COPY
command, it only establishes 1 connection.
As discussed here (https://github.com/citusdata/citus/pull/3849#pullrequestreview-431792473),
COPY needs to reserve connections up-front, otherwise we can end
up with resource starvation/un-detected deadlocks.
* ensure propagation of CHECK statements to workers with parantheses & adjust regression test outputs
* add tests for distributing tables with simple CHECK constraints
* added test for CHECK on bool variable
Enable custom aggregates with multiple parameters to be executed on workers.
#2921 introduces distributed execution of custom aggregates. One of the limitations of this feature is that only aggregate functions with a single aggregation parameter can be pushed to worker nodes. Aim of this change is to remove that limitation and support handling of multi-parameter aggregates.
Resolves: #3997
See also: #2921
* Use CalculateUniformHashRangeIndex in HashPartitionId
INT32_MIN definition can change among different platforms hence it is
possible to get overflow, we would see crashes because of this in debian
distros. We have already solved a similar problem with introducing
CalculateUniformHashRangeIndex method, hence to solve it we can use the
same method, this also removes some duplication and has a single place
to decide that.
* Use PG_INT32_XX instead of INT32_XX to be safer
With adaptive connection management, we might have some connections
which are not fully initialized. Those connections should not be
qualified as available.
1) Rename CONNECTION_PER_PLACEMENT to REQUIRE_CLEAN_CONNECTION. This is
mostly to make things clear as the new name reveals more.
2) We also make sure that mark all the copy connections critical,
even if they are accessed earlier in the transction
The executor relies on WorkerPool, and many other places rely on WorkerNode.
With this commit, we make sure that they are sorted via the same function/logic.
Some GUCs support a list of values which is indicated by GUC_LIST_INPUT flag.
When an ALTER ROLE .. SET statement is executed, the new configuration
default for affected users and databases are stored in the
setconfig(text[]) column in a pg_db_role_setting record.
If a GUC that supports a list of values is used in an ALTER ROLE .. SET
statement, we need to split the text into items delimited by commas.
* use adaptive executor even if task-tracker is set
* Update check-multi-mx tests for adaptive executor
Basically repartition joins are enabled where necessary. For parallel
tests max adaptive executor pool size is decresed to 2, otherwise we
would get too many clients error.
* Update limit_intermediate_size test
It seems that when we use adaptive executor instead of task tracker, we
exceed the intermediate result size less in the test. Therefore updated
the tests accordingly.
* Update multi_router_planner
It seems that there is one problem with multi_router_planner when we use
adaptive executor, we should fix the following error:
+ERROR: relation "authors_range_840010" does not exist
+CONTEXT: while executing command on localhost:57637
* update repartition join tests for check-multi
* update isolation tests for repartitioning
* Error out if shard_replication_factor > 1 with repartitioning
As we are removing the task tracker, we cannot switch to it if
shard_replication_factor > 1. In that case, we simply error out.
* Remove MULTI_EXECUTOR_TASK_TRACKER
* Remove multi_task_tracker_executor
Some utility methods are moved to task_execution_utils.c.
* Remove task tracker protocol methods
* Remove task_tracker.c methods
* remove unused methods from multi_server_executor
* fix style
* remove task tracker specific tests from worker_schedule
* comment out task tracker udf calls in tests
We were using task tracker udfs to test permissions in
multi_multiuser.sql. We should find some other way to test them, then we
should remove the commented out task tracker calls.
* remove task tracker test from follower schedule
* remove task tracker tests from multi mx schedule
* Remove task-tracker specific functions from worker functions
* remove multi task tracker extra schedule
* Remove unused methods from multi physical planner
* remove task_executor_type related things in tests
* remove LoadTuplesIntoTupleStore
* Do initial cleanup for repartition leftovers
During startup, task tracker would call TrackerCleanupJobDirectories and
TrackerCleanupJobSchemas to clean up leftover directories and job
schemas. With adaptive executor, while doing repartitions it is possible
to leak these things as well. We don't retry cleanups, so it is possible
to have leftover in case of errors.
TrackerCleanupJobDirectories is renamed as
RepartitionCleanupJobDirectories since it is repartition specific now,
however TrackerCleanupJobSchemas cannot be used currently because it is
task tracker specific. The thing is that this function is a no-op
currently.
We should add cleaning up intermediate schemas to DoInitialCleanup
method when that problem is solved(We might want to solve it in this PR
as well)
* Revert "remove task tracker tests from multi mx schedule"
This reverts commit 03ecc0a681.
* update multi mx repartition parallel tests
* not error with task_tracker_conninfo_cache_invalidate
* not run 4 repartition queries in parallel
It seems that when we run 4 repartition queries in parallel we get too
many clients error on CI even though we don't get it locally. Our guess
is that, it is because we open/close many connections without doing some
work and postgres has some delay to close the connections. Hence even
though connections are removed from the pg_stat_activity, they might
still not be closed. If the above assumption is correct, it is unlikely
for it to happen in practice because:
- There is some network latency in clusters, so this leaves some times
for connections to be able to close
- Repartition joins return some data and that also leaves some time for
connections to be fully closed.
As we don't get this error in our local, we currently assume that it is
not a bug. Ideally this wouldn't happen when we get rid of the
task-tracker repartition methods because they don't do any pruning and
might be opening more connections than necessary.
If this still gives us "too many clients" error, we can try to increase
the max_connections in our test suite(which is 100 by default).
Also there are different places where this error is given in postgres,
but adding some backtrace it seems that we get this from
ProcessStartupPacket. The backtraces can be found in this link:
https://circleci.com/gh/citusdata/citus/138702
* Set distributePlan->relationIdList when it is needed
It seems that we were setting the distributedPlan->relationIdList after
JobExecutorType is called, which would choose task-tracker if
replication factor > 1 and there is a repartition query. However, it
uses relationIdList to decide if the query has a repartition query, and
since it was not set yet, it would always think it is not a repartition
query and would choose adaptive executor when it should choose
task-tracker.
* use adaptive executor even with shard_replication_factor > 1
It seems that we were already using adaptive executor when
replication_factor > 1. So this commit removes the check.
* remove multi_resowner.c and deprecate some settings
* remove TaskExecution related leftovers
* change deprecated API error message
* not recursively plan single relatition repartition subquery
* recursively plan single relation repartition subquery
* test depreceated task tracker functions
* fix overlapping shard intervals in range-distributed test
* fix error message for citus_metadata_container
* drop task-tracker deprecated functions
* put the implemantation back to worker_cleanup_job_schema_cachesince citus cloud uses it
* drop some functions, add downgrade script
Some deprecated functions are dropped.
Downgrade script is added.
Some gucs are deprecated.
A new guc for repartition joins bucket size is added.
* order by a test to fix flappiness
Here are the updated make targets:
- install: install everything except downgrade scripts.
- install-downgrades: build and install only the downgrade migration scripts.
- install-all: install everything along with the downgrade migration scripts.
The reason we should use ActiveReadableNodeList instead of ActiveReadableNonCoordinatorNodeList is that if coordinator is added to cluster as a worker, it should be counted as well. Otherwise if there is only coordinator in the cluster, the count will be 0, hence we get a warning.
In MultiTaskTrackerExecute, we should connect to coordinator if it is
added to the cluster because it will also be assigned tasks.
ActiveReadableWorkerNodeList doesn't include coordinator, however if
coordinator is added as a worker, we should also include that while
planning. The current methods are very easily misusable and this
requires a refactoring to make the distinction between methods that
include coordinator and that don't very explicit as they can introduce
subtle/major bugs pretty easily.
We were using ALL_WORKERS TargetWorkerSet while sending temporary schema
creation and cleanup. We(well mostly I) thought that ALL_WORKERS would also include coordinator when it is added as a worker. It turns out that it was FILTERING OUT the coordinator even if it is added as a worker to the cluster.
So to have some context here, in repartitions, for each jobId we create
(at least we were supposed to) a schema in each worker node in the cluster. Then we partition each shard table into some intermediate files, which is called the PARTITION step. So after this partition step each node has some intermediate files having tuples in those nodes. Then we fetch the partition files to necessary worker nodes, which is called the FETCH step. Then from the files we create intermediate tables in the temporarily created schemas, which is called a MERGE step. Then after evaluating the result, we remove the temporary schemas(one for each job ID in each node) and files.
If node 1 has file1, and node 2 has file2 after PARTITION step, it is
enough to either move file1 from node1 to node2 or vice versa. So we
prune one of them.
In the MERGE step, if the schema for a given jobID doesn't exist, the
node tries to use the `public` schema if it is a superuser, which is
actually added for testing in the past.
So when we were not sending schema creation comands for each job ID to
the coordinator(because we were using ALL_WORKERS flag, and it doesn't
include the coordinator), we would basically not have any schemas for
repartitions in the coordinator. The PARTITION step would be executed on
the coordinator (because the tasks are generated in the planner part)
and it wouldn't give us any error because it doesn't have anything to do
with the temporary schemas(that we didn't create). But later two things
would happen:
- If by chance the fetch is pruned on the coordinator side, we the other
nodes would fetch the partitioned files from the coordinator and execute
the query as expected, because it has all the information.
- If the fetch tasks are not pruned in the coordinator, in the MERGE
step, the coordinator would either error out saying that the necessary
schema doesn't exist, or it would try to create the temporary tables
under public schema ( if it is a superuser). But then if we had the same
task ID with different jobID it would fail saying that the table already
exists, which is an error we were getting.
In the first case, the query would work okay, but it would still not do
the cleanup, hence we would leave the partitioned files from the
PARTITION step there. Hence ensure_no_intermediate_data_leak would fail.
To make things more explicit and prevent such bugs in the future,
ALL_WORKERS is named as ALL_NON_COORD_WORKERS. And a new flag to return
all the active nodes is added as ALL_DATA_NODES. For repartition case,
we don't use the only-reference table nodes but this version makes the
code simpler and there shouldn't be any significant performance issue
with that.
DESCRIPTION: Force aliases in deparsing for queries with anonymous column references
Fixes: #3985
The root cause has todo with discrepancies in the query tree we create. I think in the future we should spend some time on categorising all changes we made to ruleutils and see if we can change the data structure `query` we pass to the deparser to have an actual valid postgres query for the deparser to render.
For now the fix is to keep track, besides changing the names of the entries in the target list, also if we have a reference to an anonymous columns. If there are anonymous columns we set the `printaliases` flag to true which forces the deparser to add the aliases.
Rename TargetWorkerSet enums to make them more explicit about what they
mean. Ideally it would be good to treat everything as a node without the
'worker' concept because it makes things complicated. Another
improvement could be to rename TargetWorkerSet as TargetNodeSet but it
goes to renaming many occurrences of Worker, which is probably too big
for this PR.
Static analysis found some issues where we used the result from
ExtractResultRelationRTE, without checking that it wasn't NULL. It seems
like in all these cases it can never actually be NULL, since we have checked
before that it isn't a SELECT query. So, this PR is mostly to make static
analysis happy (and protect a bit against future changes of the code).
Static analysis found an issue where we could dereference `NULL`, because
`CreateDummyPlacement` could return `NULL` when there were no workers. This
PR changes it so that it never returns `NULL`, which was intended by
@marcocitus when doing this change: https://github.com/citusdata/citus/pull/3887/files#r438136433
While adding tests for citus on a single node I also added some more basic
tests and it turns out we error out on repartition joins. This has been
present since `shouldhaveshards` was introduced and is not trivial to fix.
So I created a separate issue for this: https://github.com/citusdata/citus/issues/3996
We keep accumulating more and more scripts to flag issues in CI. This is
good, but we are currently missing consistent documentation for them.
This commit moves all these scripts to the `ci` directory and adds some
documentation for all of them in the README. It also makes sure that the
last line of output of a failed script points to this documentation.
#3866 removed the shard ID hash in metadata_cache.c to simplify cache management,
but we observed a significant performance regression that was being masked by the
performance improvement provided by #3654 in our benchmarks, but #3654 only
applies to specific workloads.
This PR brings back the shard ID cache as it existed before #3866 with some extra
measures to handle invalidation. When we load a table entry, we overwrite
ShardIdCacheEntry->tableEntry pointers for all the shards in that table, though
it's possible that the table no longer contains the old shard ID or the table
entry is never reloaded, which would leave a dangling pointer once the table
entry is freed. To handle that case, we remove all shard ID cache entries that
point exactly to that table entry when a table is freed (at the end of the
transaction or any call to CitusTableCacheFlushInvalidatedEntries).
Co-authored-by: SaitTalhaNisanci <s.talhanisanci@gmail.com>
Co-authored-by: Marco Slot <marco.slot@gmail.com>
Co-authored-by: Jelte Fennema <github-tech@jeltef.nl>
It was possible to get an assertion error, if a DML command was
cancelled that opened a connection and then "ROLLBACK TO SAVEPOINT" was
used to continue the transaction. The reason for this was that canceling
the transaction might leave the `claimedExclusively` flag on for (some
of) it's connections.
This caused an assertion failure because `CanUseExistingConnection`
would return false and a new connection would be opened, and then there
would be two connections doing DML for the same placement. Which is
disallowed. That this situation caused an assertion failure instead of
an error, means that without asserts this could possibly result in some
visibility bugs, similar to the ones described
https://github.com/citusdata/citus/issues/3867
This is so we don't need to calculate it twice in
insert_select_executor.c and multi_explain.c, which can
cause discrepancy if an update in one of them is not
reflected in the other site.
* Not set TaskExecution with adaptive executor
Adaptive executor is using a utility method from task tracker for
repartition joins, however adaptive executor doesn't need taskExecution.
It is only used by task tracker. This causes a problem when explain
analyze is used because what taskExecution is pointing to might be
random.
We solve this by not setting taskExecution from adaptive executor. So it
will stay NULL as set by CreateTask.
* use same memory context as task for taskExecution
Co-authored-by: Jelte Fennema <github-tech@jeltef.nl>
As suggested by @marcocitus in https://github.com/citusdata/citus/pull/3911#issuecomment-643978531, there was
a regression in #3893. If another backend would write a file during deletion of
the intermediate results directory, this file would not necessarily be deleted.
The approach used in `CitusRemoveDirectory` is to try recursive removal of the
directory again if it has failed. This does not work here, since when a file
can not be removed for other reasons (e.g. `EPERM`) it will not throw an error
anymore. So then we would get into an infinite removal loop. Instead I now
`rename` the directory before removing it. That way other backends will not
write files to it anymore.
We sort the workerList because adaptive connection management
(e.g., OPTIONAL_CONNECTION) requires any concurrent executions
to wait for the connections in the same order to prevent any
starvation. If we don't sort, we might end up with:
Execution 1: Get connection for worker 1, wait for worker 2
Execution 2: Get connection for worker 2, wait for worker 1
and, none could proceed. Instead, we enforce every execution establish
the required connections to workers in the same order.
In #3901 the "Data received from worker(s)" sections were added to EXPLAIN
ANALYZE. After merging @pykello posted some review comments. This addresses
those comments as well as fixing a other issues that I found while addressing
them. The things this does:
1. Fix `EXPLAIN ANALYZE EXECUTE p1` to not increase received data on every
execution
2. Fix `EXPLAIN ANALYZE EXECUTE p1(1)` to not return 0 bytes as received data
allways.
3. Move `EXPLAIN ANALYZE` specific logic to `multi_explain.c` from
`adaptive_executor.c`
4. Change naming of new explain sections to `Tuple data received from node(s)`.
Firstly because a task can reference the coordinator too, so "worker(s)" was
incorrect. Secondly to indicate that this is tuple data and not all network
traffic that was performed.
5. Rename `totalReceivedData` in our codebase to `totalReceivedTupleData` to
make it clearer that it's a tuple data counter, not all network traffic.
6. Actually add `binary_protocol` test to `multi_schedule` (woops)
7. Fix a randomly failing test in `local_shard_execution.sql`.
Shard id to index mapping stored in cache entry as there may now be multiple entries alive for a given relation
insert_select_executor: revert copying cache entry, which was a hack added to avoid memory safety issues
Sadly this does not actually work yet for binary protocol data, because
when doing EXPLAIN ANALYZE we send two commands at the same time. This
means we cannot use `SendRemoteCommandParams`, and thus cannot use the
binary protocol. This can still be useful though when using the text
protocol, to find out that a lot of data is being sent.
* Insert select with master query
* Use relid to set custom_scan_tlist varno
* Reviews
* Fixes null check
Co-authored-by: Marco Slot <marco.slot@gmail.com>
This can save a lot of data to be sent in some cases, thus improving
performance for which inter query bandwidth is the bottleneck.
There's some issues with enabling this as default, so that's currently not done.
DESCRIPTION: Adds support to partially push down tdigest aggregates
tdigest extensions: https://github.com/tvondra/tdigest
This PR implements the partial pushdown of tdigest calculations when possible. The extension adds a tdigest type which can be combined into the same structure. There are several aggregate functions that can be used to get;
- a quantile
- a list of quantiles
- the quantile of a hypothetical value
- a list of quantiles for a list of hypothetical values
These function can work both on values or tdigest types.
Since we can create tdigest values either by combining them, or based on a group of values we can rewrite the aggregates in such a way that most of the computation gets delegated to the compute on the shards. This both speeds up the percentile calculations because the values don't have to be sorted while at the same time making the transfer size from the shards to the coordinator significantly less.
We still recursively plan some cases, eg:
- INSERTs
- SELECT FOR UPDATE when reference tables in query
- Everything must be same single shard & replication model
We wrap worker tasks in worker_save_query_explain_analyze() so we can fetch
their explain output later by a call worker_last_saved_explain_analyze().
Fixes#3519Fixes#2347Fixes#2613Fixes#621
This code is not needed anymore since #3668 was merged.
It's actually causing some issues when using the binary Postgres
protocol, because postgres thinks it gets a `bigint` from
the worker, but actually gets an normal `int`.
The query in question that fails is this:
```sql
CREATE TABLE test_table_1(id int, val1 int);
CREATE TABLE test_table_2(id int, val1 bigint);
SELECT create_distributed_table('test_table_1', 'id');
SELECT create_distributed_table('test_table_2', 'id');
INSERT INTO test_table_1 VALUES(1,1),(2,2),(3,3);
INSERT INTO test_table_2 VALUES(1,1),(3,3),(4,5);
SELECT val1
FROM test_table_1 LEFT JOIN test_table_2 USING(id, val1)
ORDER BY 1;
```
The difference in queries that is sent to the workers after this change is this, for this query:
```diff
--- query_old.sql 2020-06-09 09:51:21.460000000 +0200
+++ query_new.sql 2020-06-09 09:51:39.500000000 +0200
@@ -1 +1 @@
-SELECT worker_column_1 AS val1 FROM (SELECT test_table_1.val1 AS worker_column_1 FROM (public.test_table_1_102015 test_table_1(id, val1) LEFT JOIN public.test_table_2_102019 test_table_2(id, val1) USING (id, val1))) worker_subquery
+SELECT worker_column_1 AS val1 FROM (SELECT val1 AS worker_column_1 FROM (public.test_table_1_102015 test_table_1(id, val1) LEFT JOIN public.test_table_2_102019 test_table_2(id, val1) USING (id, val1))) worker_subquery
```
This is a different version of #3634. It also removes SwallowErrors, but
instead of modifying our own functions to not throw errors, it uses the
postgres built in `PathNameDeleteTemporaryDir` function. This function
does not throw errors.
Since this change is for a bugfix, I tried to minimize the changes.
PRs with the following changes would be good to do separately from this
PR:
1. Use PathName(Create|Open|Delete)Temporary(File|Dir) to open and
remove all files/dirs instead of our own custom file functions.
2. Prefix our outmost files/directories with `PG_TEMP_FILE_PREFIX` so
that they are identified by Postgres as temporary files, which will be
removed at postmaster start. This way we do not have to do this cleanup
ourselves.
3. Store the files in the temporary table space if it exists.
Fixes#3634Fixes#3618
Implements worker_save_query_explain_analyze and worker_last_saved_explain_analyze.
worker_save_query_explain_analyze executes and returns results of query while
saving its EXPLAIN ANALYZE to be fetched later.
worker_last_saved_explain_analyze returns the saved EXPLAIN ANALYZE result.
If we want to get necessary lockmode for a relation RangeVar within
a query, we can get the lockmode easily from the RangeVar itself (if
pg version >= 12).
However, if we want to decide the lockmode appropriate for the
"query", we can derive this information by using GetQueryLockMode
according to the code comment from RangeTblEntry->rellockmode.
Implements a new `TupleDestination` interface to allow custom tuple processing per task.
This can be specially useful if a task contains multiple queries. An example of this EXPLAIN
ANALYZE, where it needs to add some UDF calls to the query to fetch the explain output
from worker after fetching the actual query results.
We should check the remove type in IsDropCitusStmt because if the remove
type is not OBJECT_EXTENSION then the stored objects in
dropStmt->objects may not be of type Value. This was crashing PG-13.
Also rename the method as IsDropCitusExtensionStmt.
To reduce code duplication, implement function that pushes search_path
to be NIL and sets addCatalog to true so that all objects outside of
pg_catalog will be schema-prefixed.
Append IF NOT EXISTS to CREATE SERVER commands generated by
pg_get_serverdef_string function when deparsing an existing server
object that a foreign table depends.
SELECT_TASK is renamed to READ_TASK as a SELECT with modifying CTEs will be a MODIFYING_TASK
RouterInsertJob: Assert originalQuery->commandType == CMD_INSERT
CreateModifyPlan: Assert originalQuery->commandType != CMD_SELECT
Remove unused function IsModifyDistributedPlan
DistributedExecution, ExecutionParams, DistributedPlan: Rename hasReturning to expectResults
SELECTs set expectResults to true
Rename CreateSingleTaskRouterPlan to CreateSingleTaskRouterSelectPlan
Do not release AccessShareLock when closing pg_constraint to prevent
modifications to be done on pg_constraint to make sure that caller
will process valid foreign key constraints through the transaction.
This PR removes ExecuteUtilityTaskListWithoutResults and uses the same
path for local execution via ExecuteTaskListExtended.
ExecuteUtilityTaskList is added. ExecuteLocalTaskListExtended now has a
parameter for utility commands so that it can call the right method. In
order not to change the existing calls,
ExecuteTaskListExtendedInternal is added, which is the main method that
runs the execution, via local and remote execution.
DESCRIPTION: Ignore pruned target list entries in coordinator plan
The postgres planner has the ability to prune target list entries that are proven not used in the output relation. When this happens at the `CitusCustomScan` boundary we need to _not_ return these pruned columns to not upset the rest of the planner.
By using the target list the planner asks us to return we fix issues that lead to Assertion failures, and potentially could be runtime errors when they hit in a production build.
Fixes#3809
In the code, we had the assumption that if restriction information
is NULL, it means that we cannot have any disributetd tables in
the subquery.
However, for subqueries in WHERE clause, that is not the case when
the subquery is ANDed with FALSE. In that case, Citus operates
on the originalQuery (which doesn't go through the standard_planner()),
and rely on the restriction information generated by standard_plannner().
As Postgres is smart enough to no generate restriction information for
subqueries ANDed with FALSE, we hit the assertion.
The reason is that PQconnectPoll() may change the underlying
socket. If we don't rebuild the wait event set, the low level
APIs (such as epoll_ctl()) may fail due to invalid sockets.
Instead, rebuilding ensures that we'll use accurate/active sockets.
* Not append empty task in ExtractLocalAndRemoteTasks
ExtractLocalAndRemoteTasks extracts the local and remote tasks. If we do
not have a local task the localTaskPlacementList will be NIL, in this
case we should not append anything to local tasks. Previously we would
first check if a task contains a single placement or not, now we first
check if there is any local task before doing anything.
* fix copy of node task
Task node has task query, which might contain a list of strings in its
fields. We were using postgres copyObject for these lists. Postgres
assumes that each element of list will be a node type. If it is not a
node type it will error.
As a solution to that, a new macro is introduced to copy a list of
strings.
The previous default was 5 seconds, and we change it to 30 seconds.
The main motivation for this is that for busy clusters, 5 seconds
can be too aggressive. Especially with connection throttling, the servers
might be kept busy for a really long time, and users may see the
connection errors more frequently.
We've done some sanity checks, for really quick queries (like
`SELECT count(*) from table`), 30 seconds is a decent value even
if users execute 300 distributed queries on the coordinator. We've
verified this on Hyperscale(Citus).
Physical planner doesn't support parameters. If the parameters have already
been resolved when the physical planner handling the queries, mark it.
The reason is that the executor is unaware of this, and sends the parameters
along with the worker queries, which fails for composite types.
(See `DissuadePlannerFromUsingPlan()` for the details of paramater resolving)
We currently put the actual error message to the detail part. However,
many drivers don't show detail part.
As connection errors are somehow common, and hard to trace back, can't
we added the detail to the message itself.
In addition to that, we changed "connection error" message, as it
was confusing to the users who think that the error was happening
while connecting to the coordinator. In fact, this error is showing
up when the coordinator fails to connect remote nodes.
* invalidate plan cache in master_update_node
If a plan is cached by postgres but a user uses master_update_node, then
when the plan cache is used for the updated node, they will get the old
nodename/nodepost in the plan. This is because the plan cache doesn't
know about the master_update_node. This could be a problem in prepared
statements or anything that goes into plancache. As a solution the plan
cache is invalidated inside master_update_node.
* add invalidate_inactive_shared_connections test function
We introduce invalidate_inactive_shared_connections udf to be used in
testing. It is possible that a connection count for an inactive node
will be greater than 0 and in that case it will not be removed at the
time of invalidation. However, later we don't have a mechanism to remove
it, which means that it will stay in the hash. For this not to cause a
problem, we use this udf in testing.
* move invalidate_inactive_shared_connections to udfs from test as it will be used in mx
* remove the test udf
* remove the IsInactive check
This copies over fixes from reference counting branch,
all CitusTableCacheEntry data may be freed when a GetCitusTableCacheEntry call occurs for its relationId
This fix is not complete, but reference counting is being deferred until 9.4
CopyShardInterval: remove dest parameter, always return newly allocated object
We initially considered removing entries just before any change to
pg_dist_node. However, that ended-up being very complex and making
MX even more complex.
Instead, we're switching to a simpler solution, where we remove entries
when the counter gets to 0.
With certain workloads, this may have some performance penalty. But, two
notes on that:
- When counter == 0, it implies that the cluster is not busy
- With cached connections, that's not possible
When we call SetTaskQueryString we would set the task type to
TASK_QUERY_TEXT, and some parts of the codebase rely on the fact that if
TASK_QUERY_TEXT is set, the data can be read safely. However if
SetTaskQueryString is called with a NULL taskQueryString this can cause
crashes. In that case taskQueryType will simply be set to
TASK_QUERY_NULL.
DESCRIPTION: Alter role only works for citus managed roles
Alter role was implemented before we implemented good role management that hooks into the object propagation framework. This is a refactor of all alter role commands that have been implemented to
- be on by default
- only work for supported roles
- make the citus extension owner a supported role
Instead of distributing the alter role commands for roles at the beginning of the node activation role it now _only_ executes the alter role commands for all users in all databases and in the current database.
In preparation of full role support small refactors have been done in the deparser.
Earlier tests targeting other roles than the citus extension owner have been either slightly changed or removed to be put back where we have full role support.
Fixes#2549
We had 9+ parameters in some of the functions related to execution.
Execution params is created to simplify this a bit so that we can set
only the fields that we are interested in and it is easier to read.
With this commit, we're introducing a new infrastructure to throttle
connections to the worker nodes. This infrastructure is useful for
multi-shard queries, router queries are have not been affected by this.
The goal is to prevent establishing more than citus.max_shared_pool_size
number of connections per worker node in total, across sessions.
To do that, we've introduced a new connection flag OPTIONAL_CONNECTION.
The idea is that some connections are optional such as the second
(and further connections) for the adaptive executor. A single connection
is enough to finish the distributed execution, the others are useful to
execute the query faster. Thus, they can be consider as optional connections.
When an optional connection is not allowed to the adaptive executor, it
simply skips it and continues the execution with the already established
connections. However, it'll keep retrying to establish optional
connections, in case some slots are open again.
We currently don't use any cursor flags in local execution, but we can
use CURSOR_OPT_PARALLEL_OK flag to potentially benefit from parallelism
when possible.
This PR:
- Declares variables when they are needed.
- Creates DoCopyFromLocalTableIntoShards for better readability.
- Doesn't use a hardcoded value, instead use a variable for better
readability.
We have two variables that are related to local execution status.
TransactionAccessedLocalPlacement and
TransactionConnectedToLocalGroup. Only one of these fields should be
set, however we didn't have any check for this contraint and it was
error prone.
What those two variables are used is that we are trying to understand if
we should use local execution, the current session, or if we should be
using a connection to execute the current query, therefore the tasks. In
the enum, now it is more clear what these variables mean.
Also, now we have a method to change the local execution status. The
method will error if we are trying to transition from a state to a wrong
state. This will help us avoid problems.
* use local executon when in a transaction block
When we are inside a transaction block, there could be other methods
that need local execution, therefore we will use local execution in a
transaction block.
* update test outputs with transaction block local execution
* add a test to verify we dont leak intermediate schemas
* test that we don't leak intermediate schemas
We have tests to make sure that we don't intermediate any intermediate
files, tables etc but we don't test if we are leaking schemas. It makes
sense to test this as well.
* remove all repartition schemas in case of error
This solution is not an ideal one but it seems to be doing the job.
We should have a more generic solution for the cleanup but it seems that
putting the cleanup in the abort handler is dangerous and it was
crashing.
It is possible to return an error in ExecuteTaskListExtended after
performing local execution with the current structure. However there is
no point in execution the local tasks if we are going to return an error
later. So the local execution is moved after the error check.
When the file does not exist, it could mean two different things.
First -- and a lot more common -- case is that a failure happened
in a concurrent backend on the same distributed transaction. And,
one of the backends in that transaction has already been roll
backed, which has already removed the file. If we throw an error
here, the user might see this error instead of the actual error
message. Instead, we prefer to WARN the user and pretend that the
file has no data in it. In the end, the user would see the actual
error message for the failure.
Second, in case of any bugs in intermediate result broadcasts,
we could try to read a non-existing file. That is most likely
to happen during development. Thus, when asserts enabled, we throw
an error instead of WARNING so that the developers cannot miss.
When we have a query like the following:
```SQL
WITH a AS (SELECT * FROM foo LIMIT 10) SELECT max(x) FROM a JOIN bar 2 USING (y);
```
Citus currently opens side channels for doing the
`COPY "1_1"` FROM STDIN (format 'result')
before starting the execution of
`SELECT * FROM foo LIMIT 10`
Since we need at least 1 connection per worker to do
`SELECT * FROM foo LIMIT 10`
We need to have 2 connections to worker in order to broadcast the results.
However, we don't actually send a single row over the side channel until the
execution of `SELECT * FROM foo LIMIT 10` is completely done (and connections
unclaimed) and the results are written to a tuple store. We could actually
reuse the same connection for doing the `COPY "1_1"` FROM STDIN (format 'result').
This also fixes the issue that Citus doesn't obey `citus.max_adaptive_executor_pool_size`
when the query includes an intermediate result.
We don't need any side channel connections. That is actually
problematic in the sense that it creates extra connections.
Say, citus.max_adaptive_executor_pool_size equals to 1, Citus
ends up using one extra connection for the intermediate results.
Thus, not obeying citus.max_adaptive_executor_pool_size.
In this PR, we remove the following entities from the codebase
to allow further commits to implement not requiring extra connection
for the intermediate results:
- The connection flag REQUIRE_SIDECHANNEL
- The function GivePurposeToConnection
- The ConnectionPurpose struct and related fields
* explicitly return false if transaction connected to local node
* not set TransactionConnectedToLocalGroup if we are writing to a file
We use TransactionConnectedToLocalGroup to prevent local execution from
happening as that might cause visibility problems. As files are visible
to all transactions, we shouldn't set this variable if we are writing to
a file.
In case we don't care about the tupleStoreState in
ExecuteLocalTaskListExtended, it could be passed as null. In that case
we will get a seg error. This changes it so that a dummy tuple store
will be created when it is null.
Do not use local execution in ExecuteTaskListOutsideTransaction.
As we are going to run the tasks outside transaction, we shouldn't use local execution.
However, there is some problem when using local execution related to
repartition joins, when we solve that problem, we can execute the tasks
coming to this path with local execution.
Also logging the local command is simplified.
normalize job id in worker_hash_partition_table in test outputs.
For shardplacements, we were setting nodeid, nodename, nodeport and
nodegroup manually. This makes it very error prone, and it seems that we
already forgot to set some of them. This would mean that they would have
their default values, e.g group id would be 0 when its group id is not
0.
So the implication is that we would have inconsistent worker metadata.
A new method is introduced, and we call the method to set those fields
now, so that as long as we call this method, we won't be setting
inconsistent metadata.
It probably makes sense to have a struct for these fields. We already
have NodeMetadata but it doesn't have nodename or nodeport. So that
could be done over another refactor to make things simpler.
This is possible whenever we aren't pulling up intermediate rows
We want to do this because this was done in 9.2,
some queries rely on the performance of grouping causing distinct values
This change was introduced when implementing window functions on coordinator
ExecuteTaskListExtended is the common method for different codepaths,
and instead of writing separate local execution logics in different
codepaths, it makes more sense to have the logic here. We still need to
do some refactoring, this is an initial step.
After this commit, we can run create shard commands locally. There is a
special case with shard creation commands. A create shard command might
have a concatenated query string, however local execution did not know
how to execute a task with multiple query strings. This is also
implemented in this commit. We go over each query in the concatenated
query string and plan/execute them one by one.
A more clean solution to this would be to make sure that each task has a
single query. We currently cannot do that because we need to ensure the
task dependencies. However, it would make sense to do that at some point
and it would simplify the code a lot.
ExecuteLocalTaskList doesn't need scanState as it only uses
paramListInfo, distributedPlan and tupleStoreState. It is better to pass
only the variables that the function needs, so that we can call this
function from other places when we dont have scanState.
We had many fields in task related to query strings. It was kind of
complex, and only of them could be set at a time. Therefore it makes
more sense to abstract this and use a union so that it is clear that
only of them should be set.
We have three fields that could have query related strings:
- queryForLocation
- queryStringLazy
- perPlacementQueryStrings
Relatively, they can be set with:
- SetTaskQueryString
- SetTaskQueryIfShouldLazyDeparse
- SetTaskPerPlacementQueryStrings
The direct usage of the query related fields are also removed.
Rename queryForLocalExecution
Currently queryForLocalExecution is only used for deparsing purposes,
therefore it makes sense to rename it to what it is doing.
TaskQueryStringForPlacement simplifies how the executor gets the query
string for a given placement. Task will use the necessary fields to
return the correct query placement string. Executor doesn't need to know
the details for this.
rename TaskQueryString as TaskQueryStringAllPlacements
TaskQueryString returns the query string that will be the same for all
the placements. In INSERT..SELECT the query string can be different for
each placement. Adaptive executor uses TaskQueryStringForPlacement,
which returns the query string for a placement. It makes sense to rename
TaskQueryString as TaskQueryStringAllPlacements as it is returning the
query string for all placements.
rename SetTaskQuery as SetTaskQueryIfShouldLazyDeparse
SetTaskQuery does not always sets the task query. It can set the query
string as well. So it is more clear to name it
SetTaskQueryIfShouldLazyDeparse, since it will set the query not query
string only when we should deparse the query in a lazy way.
It is possible that a task will have different query string for each
placement. This is the case in INSERT..SELECT via repartitioning. When
we are setting task->perPlacementQueryString, we should set
queryStringLazy to NULL. Therefore a method for that purpose is created.
In PostgreSQL, user defaults for config parameters can be changed by
ALTER ROLE .. SET statements. We wish to propagate those defaults
accross the Citus cluster so that the behaviour will be similar in
different workers.
The defaults can either be set in a specific database, or the whole
cluster, similarly they can be set for a single role or all roles.
We propagate the ALTER ROLE .. SET if all the conditions below are met:
- The query affects the current database, or all databases
- The user is already created in worker nodes
Sometimes we have concatenated query strings for a task. However,
when we want to find each query string, it is not a trivial task.
Therefore, it makes sense to store this in task so that when we need
each query string we can easily get it.
Some refactoring:
Consolidate expression which decides whether GROUP BY/HAVING are pushed down
Rename early pullUpIntermediateRows to hasNonDistributableAggregates
Create WorkerColumnName to handle formatting WORKER_COLUMN_FORMAT
Ignore NULL StringInfo pointers to SafeToPushdownWindowFunction
Fix bug where SubqueryPushdownMultiNodeTree mutates supplied Query,
SafeToPushdownWindowFunction requires the original query as it relies on rtable
DESCRIPTION: Refactor dependency resolution and resolve from pg_shdepend
This PR refactors how dependencies are resolved by not assuming solely a `pg_depend` record describing the dependency. Instead we keep a definition of the dependency around which records how the dependency is resolved. This can be one of the following ways
- `pg_depend`, data will contain a copy of the `pg_depend` record
- `pg_shdepend`, data will contain a copy of the `pg_shdepend` record
- `ObjectAddress`, data will contain only an `ObjectAddress` describing a dependency
Irregardless of way the dependency was found it will always be able to get to the address of the dependency as that is the most important property.
For some checks we can inspect the source where the dependency was found and perform a deep inspection to decide if we want to follow the dependency. This is important to not distribute dependencies coming from extensions for example.
We cache connections between nodes in our connection management code.
This is good for speed. For security this can be a problem though. If
the user changes settings related to TLS encryption they want those to
be applied to future queries. This is especially important when they did
not have TLS enabled before and now they want to enable it. This can
normally be achieved by changing citus.node_conninfo. However, because
connections are not reopened there will still be old connections that
might not be encrypted at all.
This commit changes that by marking all connections to be shutdown at
the end of their current transaction. This way running transactions will
succeed, even if placement requires connections to be reused for this
transaction. But after this transaction completes any future statements
will use a connection created with the new connection options.
If a connection is requested and a connection is found that is marked
for shutdown, then we don't return this connection. Instead a new one is
created. This is needed to make sure that if there are no running
transactions, then the next statement will not use an old cached
connection, since connections are only actually shutdown at the end of a
transaction.
If two tables have the same distribution column type, we implicitly
colocate them. This is useful since colocation has a big performance
impact in most applications.
When a table is rebalanced, all of the colocated tables are also
rebalanced. If table A and table B are colocated and we want to
rebalance table A, table B will also be rebalanced. We need replica
identity so that logical replication can replicate updates and deletes
during rebalancing. If table B does not have a replica identity we
error out.
A solution to this is to introduce a UDF so that colocation can be
updated. The remaining tables in the colocation group will stay
colocated. For example if table A, B and C are colocated and after
updating table B's colocations, table A and table C stay colocated.
The "updating colocation" step does not move any data around, it only
updated pg_dist_partition and pg_dist_colocation tables. Specifically it
creates a new colocation group for the table and updates the entry in
pg_dist_partition while invalidating any cache.
Citus coordinator (or MX nodes) caches `citus.max_cached_conns_per_worker` connections
per node. This means that, those connections are not terminated after each statement.
Instead, cached to avoid the cost of re-establishment. This is crucial for OLTP performance.
The problem with that approach is that, we never properly handle the termnation of
those cached connections. For instance, when a session on the coordinator disconnects,
you'd see the following logs on the workers:
```
2020-03-20 09:13:39.454 CET [64028] LOG: could not receive data from client: Connection reset by peer
```
With this patch, we're terminating the cached connections properly at the end of the connection.
This is needed to automatically generate .bc (bitcode) files when
postgres is compiled with llvmjit support.
It also has the advantage that cmake is not required for the build
anymore.
As discussed with @JelteF; #3559 caused consistent errors on BSD (OSX). Given a group of people use this environment to develop on it is an undesirable change.
This reverts commit ca8f7119fe.
We have special logic to copy into intermediate results and we use a
custom format for that, "result" copy format. Postgres internally does
not know this format and if we use this locally it will error saying
that it does not know this format.
Files are visible to all transactions, which means that we can use any
connection to access files. In order to use the existing logic, it makes
sense that in case we have intermediate results, which means we will
write the results to a file, we preserve the same behavior, which is
opening connections to localhost. Therefore if we have intermediate
results we return false in ShouldExecuteCopyLocally.
We can use local copy in INSERT..SELECT, so the check that disables
local execution is removed.
Also a test for local copy where the data size >
LOCAL_COPY_FLUSH_THRESHOLD is added.
use local execution with insert..select
If current transaction is connected to local group we should not use
local copy, because we might not see some of the changes that are made
over the connection to the local group.
A copy will be executed locally if
- Local execution is enabled and current transaction accessed a local placement
- Local execution is enabled and we are inside a transaction block.
So even if local execution is enabled but we are not in a transaction block, the copy will not be run locally.
This will not run locally:
```
COPY distributed_table FROM STDIN;
....
```
This will run locally:
```
SET citus.enable_local_execution to 'on';
BEGIN;
COPY distributed_table FROM STDIN;
COMMIT;
....
```
.
There are 3 ways to do a copy in postgres programmatically:
- from a file
- from a program
- from a callback function
I have chosen to implement it with a callback function, which means that we write the rows of copy from a callback function to the output buffer, which is used to insert tuples into the actual table.
For each shard id, we have a buffer that keeps the current rows to be written, we perform the actual copy operation either when:
- copy buffer for the given shard id reaches to a threshold, which is currently 512KB
- we reach to the end of the copy
The buffer size is debatable(512KB). At a given time, we might allocate (local placement * buffer size) memory at most.
The local copy uses the same copy format as remote copy, which means that we serialize the data in the same format as remote copy and send it locally.
There was also the option to use ExecSimpleRelationInsert to insert
slots one by one, which would avoid the extra
serialization/deserialization but doing some benchmarks it seems that
using buffers are significantly better in terms of the performance.
You can see this comment for more details: https://github.com/citusdata/citus/pull/3557#discussion_r389499054
On some distros (e.g. Redhat 7) there is cmake version 2 and cmake version 3,
safestringlib requires cmake version 3. On those distros the binary is called
cmake3, so try to use that one before falling back to regular cmake binary.
DESCRIPTION: Fix left join shard pruning in pushdown planner
Due to #2481 which moves outer join planning through the pushdown planner we caused a regression on the shard pruning behaviour for outer joins.
In the pushdown planner we make a union of the placement groups for all shards accessed by a query based on the filters we see during planning. Unfortunately implicit filters for left joins are not available during this part. This causes the inner part of an outer join to not prune any shards away. When we take the union of the placement groups it shows the behaviour of not having any shards pruned.
Since the inner part of an outer query will not return any rows if the outer part does not contain any rows we have observed we do not have to add the shard intervals of the inner part of an outer query to the list of shard intervals to query.
Fixes: #3512
* reimplement ExecuteUtilityTaskListWithoutResults for local utility command execution
* introduce new functions for local execution of utility commands
* change ErrorIfTransactionAccessedPlacementsLocally logic for local utility command execution
* enable local execution for TRUNCATE command on distributed & reference tables
* update existing tests for local utility command execution
* enable local execution for DDL commands on distributed & reference tables
* enable local execution for DROP command on distributed & reference tables
* add normalization rules for cascaded commands
* add new tests for local utility command execution
In between stat at the start of the loop and unlink/rmdir at the end the
item that the filename references might have changed. In some cases this
can be a security bug, but since we only delete the file/directory it
should not be for us as far as I can tell. It could in theory still
cause errors though if the a file is changed into a directory by some
other process. This commit makes the code robust against that, by not
using stat and only rely on error codes and retries.
This fixes 3 bugs:
1. `strtoul` never underflows, so that branch was useless
2. `strtoul` has ULONG_MAX instead of LONG_MAX when it overflows
3. `long` and `unsigned long` are not necessarily 64bit, they can be
either more or less. So now `strtoll` and `strtoull` are used
and 64 bit bounds are checked.
New stack memory can contain anything including passwords/private keys.
In these functions we return structs that can have their padding
bytes uninitialized. By first zeroing out the struct fully, we try to
ensure that any data that is in these padding bytes is at least
overwritten once. It might not be zero anymore after setting the fields,
but at least it shouldn't be private data anymore.
Calling ErrorIfUnsupportedConstraint was still giving errors on Semmle. This
makes sure that we check for NULL at runtime. This way we can safely ignore all
errors created by this function.
Add failing tests, make changes to avoid crashes at least
Fix HAVING subquery pushdown ignoring reference table only subqueries,
also include HAVING in recursive planning
Given that we have a function IsDistributedTable which includes reference tables,
it seems best to have IsDistributedTableRTE & QueryContainsDistributedTableRTE
reflect that they do not include reference tables in their check
Similarly SublinkList's name should reflect that it only scans WHERE
contain_agg_clause asserts that we don't have SubLinks,
use contain_aggs_of_level as suggested by pg sourcecode
Before this commit, we considered !ContainsRecurringRTE() enough
for NotContainsOnlyRecurringTuples. However, instead, we can check
for existince of any distributed table.
DESCRIPTION: Fixes a bug that causes wrong results with complex outer joins
When ExecutorSlowStartInterval is set to 0, it has a special meaning
that we do not want to use slow start. Therefore, in the code we have
checks such as ExecutorSlowStartInterval > 0 to understand if it is
enabled or not. However, this is kind of subtle, and it creates an extra
mapping in our mind. Therefore, I thought that using a variable for the
special value removes the mapping and makes it easier to understand.
As @onderkalaci suggested removing the definition of GetWorkerNodeCount() that can potentially cause misunderstandings.
I can advise using ActiveReadableWorkerNodeCount() that returns the number of active primaries is a safer alternative than GetWorkerNodeCount() that returns the total number of workers containing inactives, primaries, and unavailable nodes. I introduced a bug #3556 and in the bugfix #3564 removed the single usage of said function
There are 2 problems with our early exit strategy that this commit fixes:
1- When we decide that a subplan results are sent to all worker nodes,
we used to skip traversing the whole distributed plan, instead of
skipping only the subplan.
2- We used to consider all available nodes in the cluster (secondaries
and inactive nodes as well as active primaries) when deciding on early
exit strategy. This resulted in failures to early exit when there are
secondaries or inactive nodes.
DESCRIPTION: satisfy static analysis tool for a nullptr dereference
During the static analysis project on the codebase this code has been flagged as having the potential for a null pointer dereference. Funnily enough the author had already made a comment of it in the code this was not possible due to us setting the schema name before we pass in the statement. If we want to reuse this code in a later setting this comment might not always apply and we could actually run into null pointer dereference.
This patch changes a bit of the code around to first of all make sure there is no NULL pointer dereference in this code anymore.
Secondly we allow for better deparsing by setting and adhering to the `if_not_exists` flag on the statement.
And finally add support for all syntax described in the documentation of postgres (FROM was missing).
Makees VacuumTaskList function even with other TaskList creator functions.
Also, previously we were generating per-shard vacuum command strings via
unconventional usage of StringInfo struct (setting the stringInfo->len field
manually) which could cause unexepected memory errors (that I cannot foresee now).
If the generated column does not come at the end of the column list,
columnNameList doesn't line up with the column indexes. Seek past
CREATE TABLE test_table (
test_id int PRIMARY KEY,
gen_n int GENERATED ALWAYS AS (1) STORED,
created_at TIMESTAMPTZ NOT NULL DEFAULT now()
);
SELECT create_distributed_table('test_table', 'test_id');
Would raise ERROR: cannot cast 23 to 1184
Semmle reported quite some places where we use a value that could be NULL. Most of these are not actually a real issue, but better to be on the safe side with these things and make the static analysis happy.
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