This change adds `start_metadata_sync_to_node` UDF which copies the metadata about nodes and MX tables
from master to the specified worker, sets its local group ID and marks its hasmetadata to true to
allow it receive future DDL changes.
One less place managing remote transactions. It also makes it fairly
easy to use 2PC for certain modifications (e.g. reference tables). Just
issue a CoordinatedTransactionUse2PC(). If every placement failure
should cause the whole transaction to abort, additionally mark the
relevant transactions as critical.
With this PR, we add foreign key support to ALTER TABLE commands. For now,
we only support foreign constraint creation via ALTER TABLE query, if it
is only subcommand in ALTER TABLE subcommand list.
We also only allow foreign key creation if replication factor is 1.
That way connections can be automatically closed after errors and such,
and the connection management infrastructure gets wider testing. It
also fixes a few issues around connection string building.
This includes basic infrastructure for logging of commands sent to
remote/worker nodes. Note that this has no effect as of yet, since no
callers are converted to the new infrastructure.
Connections are tracked and released by integrating into postgres'
transaction handling. That allows to to use connections without having
to resort to having to disable interrupts or using PG_TRY/CATCH blocks
to avoid leaking connections.
This is intended to eventually replace multi_client_executor.c and
connection_cache.c, and to provide the basis of a centralized
transaction management.
The newly introduced transaction hook should, in the future, be the only
one in citus, to allow for proper ordering between operations. For now
this central handler is responsible for releasing connections and
resetting XactModificationLevel after a transaction.
This commit fixes a bug when the SELECT target list includes a constant
value.
Previous behaviour of target list re-ordering:
* Iterate over the INSERT target list
* If it includes a Var, find the corresponding SELECT entry
and update its resno accordingly
* If it does not include a Var (which we only considered to be
DEFAULTs), generate a new SELECT target entry
* If the processed target entry count in SELECT target list is less
than the original SELECT target list (GROUP BY elements not included in
the SELECT target entry), add them in the SELECT target list and
update the resnos accordingly.
* However, this step was leading to add the CONST SELECT target entries
twice. The reason is that when CONST target list entries appear in the
SELECT target list, the INSERT target list doesn't include a Var. Instead,
it includes CONST as it does for DEFAULTs.
New behaviour of target list re-ordering:
* Iterate over the INSERT target list
* If it includes a Var, find the corresponding SELECT entry
and update its resno accordingly
* If it does not include a Var (which we consider to be
DEFAULTs and CONSTs on the SELECT), generate a new SELECT
target entry
* If any target entry remains on the SELECT target list which are resjunk,
(GROUP BY elements not included in the SELECT target entry), keep them
in the SELECT target list by updating the resnos.
While creating a colocated table, we don't want the source table to be dropped.
However, using a ShareLock blocks DML statements on the source table, and
using AccessShareLock is enough to prevent DROP. Therefore, we just loosened
the lock to AccessShareLock.
This change allows seeing the names of columns of `master_add_node`,
using `SELECT * FROM master_add_node(...)` by specifying output
columns in UDF definition.
Previously, we threw an error when we ran CREATE INDEX IF NOT EXISTS
with an already existing index. This change enables expected behavior by
checking if the statement has IF NOT EXISTS before throwing the error.
We also ensure that we don't execute the command on the workers, if an
index already exists on the master.
At the moment, we do not support foreign constraints if replication factor is greater
than 1. However foreign constraints can be used in cloud with high availability option.
Therefore we do not want to create an impression such that foreign constraints with
high availability is not supported at all. We call users to action with this error
message.
In ErrorIfShardPlacementsNotColocated(), while checking if shards are colocated,
error out if matching shard intervals have different number of shard placements.
Added a new UDF, mark_tables_colocated(), to colocate tables with the same
configuration (shard count, shard replication count and distribution column type).
Fixcitusdata/citus#886
The way postgres' explain hook is designed means that our hook is never
called during EXPLAIN EXECUTE. So, we special-case EXPLAIN EXECUTE by
catching it in the utility hook. We then replace the EXECUTE with the
original query and pass it back to Citus.
Previously, when a repair is requested on a shard, we also repair all co-located shards
of given shard, which may cause repairing already healthy shards. With this change, we
only repair given shard.
This forces prepared statements to be re-planned after changes of the
placement metadata. There's some locking issues remaining, but that's a
a separate task.
Also add regression tests verifying that invalidations take effect on
prepared statements.
This commit adds INSERT INTO ... SELECT feature for distributed tables.
We implement INSERT INTO ... SELECT by pushing down the SELECT to
each shard. To compute that we use the router planner, by adding
an "uninstantiated" constraint that the partition column be equal to a
certain value. standard_planner() distributes that constraint to all
the tables where it knows how to push the restriction safely. An example
is that the tables that are connected via equi joins.
The router planner then iterates over the target table's shards,
for each we replace the "uninstantiated" restriction, with one that
PruneShardList() handles. Do so by replacing the partitioning qual
parameter added in multi_planner() with the current shard's
actual boundary values. Also, add the current shard's boundary values to the
top level subquery to ensure that even if the partitioning qual is
not distributed to all the tables, we never run the queries on the shards
that don't match with the current shard boundaries. Finally, perform the
normal shard pruning to decide on whether to push the query to the
current shard or not.
We do not support certain SQLs on the subquery, which are described/commented
on ErrorIfInsertSelectQueryNotSupported().
We also added some locking on the router executor. When an INSERT/SELECT command
runs on a distributed table with replication factor >1, we need to ensure that
it sees the same result on each placement of a shard. So we added the ability
such that router executor takes exclusive locks on shards from which the SELECT
in an INSERT/SELECT reads in order to prevent concurrent changes. This is not a
very optimal solution, but it's simple and correct. The
citus.all_modifications_commutative can be used to avoid aggressive locking.
An INSERT/SELECT whose filters are known to exclude any ongoing writes can be
marked as commutative. See RequiresConsistentSnapshot() for the details.
We also moved the decison of whether the multiPlan should be executed on
the router executor or not to the planning phase. This allowed us to
integrate multi task router executor tasks to the router executor smoothly.
The necessity for this functionality comes from the fact that ruleutils.c is not supposed to be
used on "rewritten" queries (i.e. ones that have been passed through QueryRewrite()).
Query rewriting is the process in which views and such are expanded,
and, INSERT/UPDATE targetlists are reordered to match the physical order,
defaults etc. For the details of reordeing, see transformInsertRow().
We'd been relying on a single SET search_path command in an earlier
script, but a subsequent script RESET search_path, causing any further
bare functions to be created in the first schema on the search path.
However, starting with an older extension version and executing ALTER
scripts one at a time DOES avoid putting any functions in the public
namespace, so I wrote an upgrade script resilient to that, especially
because PostgreSQL 9.5 will error out if a function is already in the
schema it's being moved to.
Between restart (running the new code) and ALTER EXTENSION citus
UPGRADE there was an inconsistency where we assumed that
pg_dist_partition had the repmodel column set. Now we give it a default
value if the column doesn't exist yet.
Marco Slot
Eren Basak
Andres Freund
Burak Yucesoy
Brian Cloutier
Onder Kalaci
Murat Tuncer
Sumedh Pathak
Metin Doslu
Samay Sharma
Jason Petersen