Need to also check Postgres plan's rangetables for relations used in Initplans.
DESCRIPTION: Fix a bug in redundant WHERE clause detection; we need to
additionally check the Postgres plan's range tables for the presence of
citus tables, to account for relations that are referenced from scalar
subqueries.
There is a fundamental flaw in 4139370, the assumption that, after
Postgres planning has completed, all tables used in a query can be
obtained by walking the query tree. This is not the case for scalar
subqueries, which will be referenced by `PARAM` nodes. The fix adds an
additional check of the Postgres plan range tables; if there is at least
one citus table in there we do not need to change the needs distributed
planning flag.
Fixes#8159
**DESCRIPTION:**
This pull request introduces the foundation and core logic for the
snapshot-based node split feature in Citus. This feature enables
promoting a streaming replica (referred to as a clone in this feature
and UI) to a primary node and rebalancing shards between the original
and the newly promoted node without requiring a full data copy.
This significantly reduces rebalance times for scale-out operations
where the new node already contains a full copy of the data via
streaming replication.
Key Highlights:
**1. Replica (Clone) Registration & Management Infrastructure**
Introduces a new set of UDFs to register and manage clone nodes:
- citus_add_clone_node()
- citus_add_clone_node_with_nodeid()
- citus_remove_clone_node()
- citus_remove_clone_node_with_nodeid()
These functions allow administrators to register a streaming replica of
an existing worker node as a clone, making it eligible for later
promotion via snapshot-based split.
**2. Snapshot-Based Node Split (Core Implementation)**
New core UDF:
- citus_promote_clone_and_rebalance()
This function implements the full workflow to promote a clone and
rebalance shards between the old and new primaries. Steps include:
1. Ensuring Exclusivity – Blocks any concurrent placement-changing
operations.
2. Blocking Writes – Temporarily blocks writes on the primary to ensure
consistency.
3. Replica Catch-up – Waits for the replica to be fully in sync.
4. Promotion – Promotes the replica to a primary using pg_promote.
5. Metadata Update – Updates metadata to reflect the newly promoted
primary node.
6. Shard Rebalancing – Redistributes shards between the old and new
primary nodes.
**3. Split Plan Preview**
A new helper UDF get_snapshot_based_node_split_plan() provides a preview
of the shard distribution post-split, without executing the promotion.
**Example:**
```
reb 63796> select * from pg_catalog.get_snapshot_based_node_split_plan('127.0.0.1',5433,'127.0.0.1',5453);
table_name | shardid | shard_size | placement_node
--------------+---------+------------+----------------
companies | 102008 | 0 | Primary Node
campaigns | 102010 | 0 | Primary Node
ads | 102012 | 0 | Primary Node
mscompanies | 102014 | 0 | Primary Node
mscampaigns | 102016 | 0 | Primary Node
msads | 102018 | 0 | Primary Node
mscompanies2 | 102020 | 0 | Primary Node
mscampaigns2 | 102022 | 0 | Primary Node
msads2 | 102024 | 0 | Primary Node
companies | 102009 | 0 | Clone Node
campaigns | 102011 | 0 | Clone Node
ads | 102013 | 0 | Clone Node
mscompanies | 102015 | 0 | Clone Node
mscampaigns | 102017 | 0 | Clone Node
msads | 102019 | 0 | Clone Node
mscompanies2 | 102021 | 0 | Clone Node
mscampaigns2 | 102023 | 0 | Clone Node
msads2 | 102025 | 0 | Clone Node
(18 rows)
```
**4 Test Infrastructure Enhancements**
- Added a new test case scheduler for snapshot-based split scenarios.
- Enhanced pg_regress_multi.pl to support creating node backups with
slightly modified options to simulate real-world backup-based clone
creation.
### 5. Usage Guide
The snapshot-based node split can be performed using the following
workflow:
**- Take a Backup of the Worker Node**
Run pg_basebackup (or an equivalent tool) against the existing worker
node to create a physical backup.
`pg_basebackup -h <primary_worker_host> -p <port> -D
/path/to/replica/data --write-recovery-conf
`
**- Start the Replica Node**
Start PostgreSQL on the replica using the backup data directory,
ensuring it is configured as a streaming replica of the original worker
node.
**- Register the Backup Node as a Clone**
Mark the registered replica as a clone of its original worker node:
`SELECT * FROM citus_add_clone_node('<clone_host>', <clone_port>,
'<primary_host>', <primary_port>);
`
**- Promote and Rebalance the Clone**
Promote the clone to a primary and rebalance shards between it and the
original worker:
`SELECT * FROM citus_promote_clone_and_rebalance('clone_node_id');
`
**- Drop Any Replication Slots from the Original Worker**
After promotion, clean up any unused replication slots from the original
worker:
`SELECT pg_drop_replication_slot('<slot_name>');
`
DESCRIPTION: Parallelizes shard rebalancing and removes the bottlenecks
that previously blocked concurrent logical-replication moves.
These improvements reduce rebalance windows—particularly for clusters
with large reference tables and enable multiple shard transfers to run in parallel.
Motivation:
Citus’ shard rebalancer has some key performance bottlenecks:
**Sequential Movement of Reference Tables:**
Reference tables are often assumed to be small, but in real-world
deployments, they can grow significantly large. Previously, reference
table shards were transferred as a single unit, making the process
monolithic and time-consuming.
**No Parallelism Within a Colocation Group:**
Although Citus distributes data using colocated shards, shard
movements within the same colocation group were serialized. In
environments with hundreds of distributed tables colocated
together, this serialization significantly slowed down rebalance
operations.
**Excessive Locking:**
Rebalancer used restrictive locks and redundant logical replication
guards, further limiting concurrency.
The goal of this commit is to eliminate these inefficiencies and enable
maximum parallelism during rebalance, without compromising correctness
or compatibility. Parallelize shard rebalancing to reduce rebalance
time.
Feature Summary:
**1. Parallel Reference Table Rebalancing**
Each reference-table shard is now copied in its own background task.
Foreign key and other constraints are deferred until all shards are
copied.
For single shard movement without considering colocation a new
internal-only UDF '`citus_internal_copy_single_shard_placement`' is
introduced to allow single-shard copy/move operations.
Since this function is internal, we do not allow users to call it
directly.
**Temporary Hack to Set Background Task Context** Background tasks
cannot currently set custom GUCs like application_name before executing
internal-only functions. 'citus_rebalancer ...' statement as a prefix in
the task command. This is a temporary hack to label internal tasks until
proper GUC injection support is added to the background task executor.
**2. Changes in Locking Strategy**
- Drop the leftover replication lock that previously serialized shard
moves performed via logical replication. This lock was only needed when
we used to drop and recreate the subscriptions/publications before each
move. Since Citus now removes those objects later as part of the “unused
distributed objects” cleanup, shard moves via logical replication can
safely run in parallel without additional locking.
- Introduced a per-shard advisory lock to prevent concurrent operations
on the same shard while allowing maximum parallelism elsewhere.
- Change the lock mode in AcquirePlacementColocationLock from
ExclusiveLock to RowExclusiveLock to allow concurrent updates within the
same colocation group, while still preventing concurrent DDL operations.
**3. citus_rebalance_start() enhancements**
The citus_rebalance_start() function now accepts two new optional
parameters:
```
- parallel_transfer_colocated_shards BOOLEAN DEFAULT false,
- parallel_transfer_reference_tables BOOLEAN DEFAULT false
```
This ensures backward compatibility by preserving the existing behavior
and avoiding any disruption to user expectations and when both are set
to true, the rebalancer operates with full parallelism.
**Previous Rebalancer Behavior:**
`SELECT citus_rebalance_start(shard_transfer_mode := 'force_logical');`
This would:
Start a single background task for replicating all reference tables
Then, move all shards serially, one at a time.
```
Task 1: replicate_reference_tables()
↓
Task 2: move_shard_1()
↓
Task 3: move_shard_2()
↓
Task 4: move_shard_3()
```
Slow and sequential. Reference table copy is a bottleneck. Colocated
shards must wait for each other.
**New Parallel Rebalancer:**
```
SELECT citus_rebalance_start(
shard_transfer_mode := 'force_logical',
parallel_transfer_colocated_shards := true,
parallel_transfer_reference_tables := true
);
```
This would:
- Schedule independent background tasks for each reference-table shard.
- Move colocated shards in parallel, while still maintaining dependency
order.
- Defer constraint application until all reference shards are in place.
-
```
Task 1: copy_ref_shard_1()
Task 2: copy_ref_shard_2()
Task 3: copy_ref_shard_3()
→ Task 4: apply_constraints()
↓
Task 5: copy_shard_1()
Task 6: copy_shard_2()
Task 7: copy_shard_3()
↓
Task 8-10: move_shard_1..3()
```
Each operation is scheduled independently and can run as soon as
dependencies are satisfied.
DESCRIPTION: Adds support for pushing down LEFT/RIGHT outer joins having
a reference table in the outer side and a distributed table on the inner
side (e.g., <reference table> LEFT JOIN <distributed table>)
Partially addresses #6546
1) `<outer:reference>` LEFT JOIN `<inner:distributed>`
2) `<inner:distributed>` RIGHT JOIN `<outer:reference>`
Previously, for outer joins of types (1) and (2), the distributed side
was computed recursively. This was necessary because, when the inner
side of a recurring outer join is a distributed table, it is not
possible to directly distribute the join; the preserved (outer and
recurring) side may generate rows with join keys that hash to different
shards.
To implement distributed planning while maintaining consistency with
global execution semantics, this PR restricts the outer side only to
those partition key values that route to the selected shard during
distributed shard query computation. This method is employed )when the
following criteria are met: (recursive planning applied otherwise)
- The join type is (1) or (2) (lateral joins are not supported).
- The outer side is a reference table.
- The outer join qualifications include an equality condition between
the partition column of a distributed table and the recurring table.
- The join is not part of a chained join.
- The “enable_recurring_outer_join_pushdown” GUC is enabled (default is
on).
---------
Co-authored-by: ebruaydingol <ebruaydingol@microsoft.com>
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
DESCRIPTION: Not automatically create citus_columnar when there are no
relations using it.
Previously, we were always creating citus_columnar when creating citus
with version >= 11.1. And how we were doing was as follows:
* Detach SQL objects owned by old columnar, i.e., "drop" them from
citus, but not actually drop them from the database
* "old columnar" is the one that we had before Citus 11.1 as part of
citus, i.e., before splitting the access method ands its catalog to
citus_columnar.
* Create citus_columnar and attach the SQL objects leftover from old
columnar to it so that we can continue supporting the columnar tables
that user had before Citus 11.1 with citus_columnar.
First part is unchanged, however, now we don't create citus_columnar
automatically anymore if the user didn't have any relations using
columnar. For this reason, as of Citus 13.2, when these SQL objects are
not owned by an extension and there are no relations using columnar
access method, we drop these SQL objects when updating Citus to 13.2.
The net effect is still the same as if we automatically created
citus_columnar and user dropped citus_columnar later, so we should not
have any issues with dropping them.
(**Update:** Seems we've made some assumptions in citus, e.g.,
citus_finish_pg_upgrade() still assumes columnar metadata exists and
tries to apply some fixes for it, so this PR fixes them as well. See the
last section of this PR description.)
Also, ideally I was hoping to just remove some lines of code from
extension.c, where we decide automatically creating citus_columnar when
creating citus, however, this didn't happen to be the case for two
reasons:
* We still need to automatically create it for the servers using
columnar access method.
* We need to clean-up the leftover SQL objects from old columnar when
the above is not case otherwise we would have leftover SQL objects from
old columnar for no reason, and that would confuse users too.
* Old columnar cannot be used to create columnar tables properly, so we
should clean them up and let the user decide whether they want to create
citus_columnar when they really need it later.
---
Also made several changes in the test suite because similarly, we don't
always want to have citus_columnar created in citus tests anymore:
* Now, columnar specific test targets, which cover **41** test sql
files, always install columnar by default, by using
"--load-extension=citus_columnar".
* "--load-extension=citus_columnar" is not added to citus specific test
targets because by default we don't want to have citus_columnar created
during citus tests.
* Excluding citus_columnar specific tests, we have **601** sql files
that we have as citus tests and in **27** of them we manually create
citus_columnar at the very beginning of the test because these tests do
test some functionalities of citus together with columnar tables.
Also, before and after schedules for PG upgrade tests are now duplicated
so we have two versions of each: one with columnar tests and one
without. To choose between them, check-pg-upgrade now supports a
"test-with-columnar" option, which can be set to "true" or anything else
to logically indicate "false". In CI, we run the check-pg-upgrade test
target with both options. The purpose is to ensure we can test PG
upgrades where citus_columnar is not created in the cluster before the
upgrade as well.
Finally, added more tests to multi_extension.sql to test Citus upgrade
scenarios with / without columnar tables / citus_columnar extension.
---
Also, seems citus_finish_pg_upgrade was assuming that citus_columnar is
always created but actually we should have never made such an
assumption. To fix that, moved columnar specific post-PG-upgrade work
from citus to a new columnar UDF, which is columnar_finish_pg_upgrade.
But to avoid breaking existing customer / managed service scripts, we
continue to automatically perform post PG-upgrade work for columnar
within citus_finish_pg_upgrade, but only if columnar access method
exists this time.
DESCRIPTION: Introduce a new check to push down a query including union
and outer join to fix#8091 .
In "SafeToPushdownUnionSubquery", we check if the distribution column of
the outer relation is in the target list.
DESCRIPTION: Fixes problematic UPDATE statements with indirection and array/jsonb subscripting with more than one field.
Fixes#4092, #7674 and #5621. Issues #7674 and #4092 involve an UPDATE with out of order columns and a sublink (SELECT) in the source, e.g. `UPDATE T SET (col3, col1, col4) = (SELECT 3, 1, 4)` where an incorrect value could get written to a column because query deparsing generated an incorrect SQL statement. To address this the fix adds an additional
check to `ruleutils` to ensure that the target list of an UPDATE statement is in an order so that deparsing can be done safely. It is needed when the source of the UPDATE has a sublink, because Postgres `rewrite` will have put the target list in attribute order, but for deparsing to produce a correct SQL text the target list needs to be in order of the references (or `paramids`) to the target list of the sublink(s). Issue #5621 involves an UPDATE with array/jsonb subscripting that can behave incorrectly with more than one field, again because Citus query deparsing is receiving a post-`rewrite` query tree. The fix also adds a
check to `ruleutils` to enable correct query deparsing of the UPDATE.
---------
Co-authored-by: Ibrahim Halatci <ihalatci@gmail.com>
Co-authored-by: Colm McHugh <colm.mchugh@gmail.com>
PG15 commit d1ef5631e620f9a5b6480a32bb70124c857af4f1
and PG16 commit 695f5deb7902865901eb2d50a70523af655c3a00
disallow replacing joins with scans in queries with pseudoconstant quals.
This commit prevents the set_join_pathlist_hook from being called
if any of the join restrictions is a pseudo-constant.
So in these cases, citus has no info on the join, never sees that
the query has an outer join, and ends up producing an incorrect plan.
PG17 fixes this by commit 9e9931d2bf40e2fea447d779c2e133c2c1256ef3
Therefore, we take this extra measure here for PG versions less than 17.
hasOuterJoin can never be true when set_join_pathlist_hook is absent.
DESCRIPTION: Adds support for issuing `CREATE`/`DROP` DATABASE commands
from worker nodes
With this commit, we allow issuing CREATE / DROP DATABASE commands from
worker nodes too.
As in #7278, this is not allowed when the coordinator is not added to
metadata because we don't ever sync metadata changes to coordinator
when adding coordinator to the metadata via
`SELECT citus_set_coordinator_host('<hostname>')`, or equivalently, via
`SELECT citus_add_node(<coordinator_node_name>, <coordinator_node_port>, 0)`.
We serialize database management commands by acquiring a Citus specific
advisory lock on the first primary worker node if there are any workers in the
cluster. As opposed to what we've done in https://github.com/citusdata/citus/pull/7278
for role management commands, we try to avoid from running into distributed deadlocks
as much as possible. This is because, while distributed deadlocks that can happen around
role management commands can be detected by Citus, this is not the case for database
management commands because most of them cannot be run inside in a transaction block.
In that case, Citus cannot even detect the distributed deadlock because the command is not
part of a distributed transaction at all, then the command execution might not return the
control back to the user for an indefinite amount of time.
This fixes#7230.
First of all, using HeapTupleHeaderGetDatumLength(heapTuple) is
definetly wrong, it gives a number that's 4 times less than the correct
tuple size (heapTuple.t_len). See
https://github.com/postgres/postgres/blob/REL_16_0/src/include/access/htup_details.h#L455-L456https://github.com/postgres/postgres/blob/REL_16_0/src/include/varatt.h#L279https://github.com/postgres/postgres/blob/REL_16_0/src/include/varatt.h#L225-L226
When I fixed it, the limit_intermediate_size test failed, so I tried to
understand what's going on there. In original commit fd546cf these
queries were supposed to fail. Then in b3af63c three of the queries that
were supposed to fail suddenly worked and tests were changed to pass
without understanding why the output had changed or how to keep test
testing what it had to test. Even comments saying that these queries
should fail were left untouched. Commit message gives no clue about why
exactly test has changed:
> 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.
Then 3fda2c3 also blindly raised the limit for one of the queries to
keep it working:
3fda2c3254 (diff-a9b7b617f9dfd345318cb8987d5897143ca1b723c87b81049bbadd94dcc86570R19)
When in fe3caf3 that HeapTupleHeaderGetDatumLength(heapTuple) call was
finally added, one of those test queries became failing again.
The other two of them now also failing after the fix. I don't understand
how exactly the calculation of "intermediate result size" that is
limited by citus.max_intermediate_result_size had changed through
b3af63c and fe3caf3, but these numbers are now closer to what
they originally were when this limitation was added in
fd546cf. So these queries should fail, like in the original
version of the limit_intermediate_size test.
Co-authored-by: Karina Litskevich <litskevichkarina@gmail.com>
foreign_key_to_reference_shard_rebalance failed because partition of
2024 year does not exist, fixed by add default partition.
Replaces https://github.com/citusdata/citus/pull/7396 by adding a rule
that allows properly testing foreign_key_to_reference_shard_rebalance
via run_test.py.
Closes#7396
Co-authored-by: chuhx <148182736+cstarc1@users.noreply.github.com>
While investigating replication slots leftovers
in PR https://github.com/citusdata/citus/pull/7338,
I ran into the following refactoring/cleanup
that can be done in our test suite:
- Add separate test to remove non default nodes
- Remove coordinator removal from `add_coordinator` test
Use `remove_coordinator_from_metadata` test where needed
- Don't print nodeids in `multi_multiuser_auth` and
`multi_poolinfo_usage`
tests
- Use `startswith` when checking for isolation or failure tests
- Add some dependencies accordingly in `run_test.py` for running flaky
test schedules
When I run this test in my local, the size of the table after the DELETE
command is around 58785792. Hence, I assume that the diffs suggest that
the Vacuum had no effect. The current solution is to run the VACUUM
command three times instead of once.
Example diff:
https://github.com/citusdata/citus/actions/runs/6722231142/attempts/1#summary-18269870674
```diff
insert into local_vacuum_table select i from generate_series(1,1000000) i;
delete from local_vacuum_table;
VACUUM local_vacuum_table;
SELECT CASE WHEN s BETWEEN 20000000 AND 25000000 THEN 22500000 ELSE s END
FROM pg_total_relation_size('local_vacuum_table') s ;
s
----------
- 22500000
+ 58785792
(1 row)
```
See more diff examples in the PR description
https://github.com/citusdata/citus/pull/7334
Fixes the flaky test that results in following diff:
```diff
--- /__w/citus/citus/src/test/regress/expected/multi_mx_node_metadata.out.modified 2023-11-01 14:22:12.890476575 +0000
+++ /__w/citus/citus/src/test/regress/results/multi_mx_node_metadata.out.modified 2023-11-01 14:22:12.914476657 +0000
@@ -840,24 +840,26 @@
(1 row)
\c :datname - - :master_port
SELECT datname FROM pg_stat_activity WHERE application_name LIKE 'Citus Met%';
datname
------------
db_to_drop
(1 row)
DROP DATABASE db_to_drop;
+ERROR: database "db_to_drop" is being accessed by other users
SELECT datname FROM pg_stat_activity WHERE application_name LIKE 'Citus Met%';
datname
------------
-(0 rows)
+ db_to_drop
+(1 row)
-- cleanup
DROP SEQUENCE sequence CASCADE;
NOTICE: drop cascades to default value for column a of table reference_table
```
I just enhanced the existing code to check if the relation is an index
belonging to a distributed table.
If so the shardId is appended to relation (index) name and the *_size
function are executed as before.
There is a change in an extern function:
`extern StringInfo GenerateSizeQueryOnMultiplePlacements(...)`
It's possible to create a new function and deprecate this one later if
compatibility is an issue.
Fixes https://github.com/citusdata/citus/issues/6496.
DESCRIPTION: Allows using Citus size functions on distributed tables
indexes.
---------
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
There was a bug reported for previous versions of Citus where
shard\_size was returning NULL for tables with spaces in them. It works
fine on the main branch though, but I'm still adding a test for this to
the main branch because it seems a good test to have.
**Problem:**
Previously we always used an outside superuser connection to overcome
permission issues for the current user while propagating dependencies.
That has mainly 2 problems:
1. Visibility issues during dependency propagation, (metadata connection
propagates some objects like a schema, and outside transaction does not
see it and tries to create it again)
2. Security issues (it is preferrable to use current user's connection
instead of extension superuser)
**Solution (high level):**
Now, we try to make a smarter decision on whether should we use an
outside superuser connection or current user's metadata connection. We
prefer using current user's connection if any of the objects, which is
already propagated in the current transaction, is a dependency for a
target object. We do that since we assume if current user has
permissions to create the dependency, then it can most probably
propagate the target as well.
Our assumption is expected to hold most of the times but it can still be
wrong. In those cases, transaction would fail and user should set the
GUC `citus.create_object_propagation` to `deferred` to work around it.
**Solution:**
1. We track all objects propagated in the current transaction (we can
handle subtransactions),
2. We propagate dependencies via the current user's metadata connection
if any dependency is created in the current transaction to address
issues listed above. Otherwise, we still use an outside superuser
connection.
DESCRIPTION: Fixes some object propagation errors seen with transaction
blocks.
Fixes https://github.com/citusdata/citus/issues/6614
---------
Co-authored-by: Nils Dijk <nils@citusdata.com>
One problem with rebalancing by disk size is that shards in newly
created collocation groups are considered extremely small. This can
easily result in bad balances if there are some other collocation groups
that do have some data. One extremely bad example of this is:
1. You have 2 workers
2. Both contain about 100GB of data, but there's a 70MB difference.
3. You create 100 new distributed schemas with a few empty tables in
them
4. You run the rebalancer
5. Now all new distributed schemas are placed on the node with that had
70MB less.
6. You start loading some data in these shards and quickly the balance
is completely off
To address this edge case, this PR changes the by_disk_size rebalance
strategy to add a a base size of 100MB to the actual size of each
shard group. This can still result in a bad balance when shard groups
are empty, but it solves some of the worst cases.
This commit is the second and last phase of dropping PG13 support.
It consists of the following:
- Removes all PG_VERSION_13 & PG_VERSION_14 from codepaths
- Removes pg_version_compat entries and columnar_version_compat entries
specific for PG13
- Removes alternative pg13 test outputs
- Removes PG13 normalize lines and fix the test outputs based on that
It is a continuation of 5bf163a27d
Allow using generated identity column based on int/smallint when
creating a distributed table so that applications that rely on
those data types don't break.
Inserting into / modifying such columns from workers is not allowed
but it's better than not allowing such columns altogether.
Changes test files in multi and multi-1 schedules such that they
accomodate coordinator in metadata.
Changes fall into the following buckets:
1. When coordinator is in metadata, reference table shards are present
in coordinator too.
This changes test outputs checking the table size, shard numbers etc.
for reference tables.
2. When coordinator is in metadata, postgres tables are converted to
citus local tables whenever a foreign key relationship to them is
created. This changes some test cases which tests it should not be
possible to create foreign keys to postgres tables.
3. Remove lines that add/remove coordinator for testing purposes.
Verify Citus UDFs work well with single shard tables
SUPPORTED
* citus_table_size
* citus_total_relation_size
* citus_relation_size
* citus_shard_sizes
* truncate_local_data_after_distributing_table
* create_distributed_function // test function colocated with a single
shard table
* undistribute_table
* alter_table_set_access_method
UNSUPPORTED - error out for single shard tables
* master_create_empty_shard
* create_distributed_table_concurrently
* create_distributed_table
* create_reference_table
* citus_add_local_table_to_metadata
* citus_split_shard_by_split_points
* alter_distributed_table
DESCRIPTION: Adds citus.enable_schema_based_sharding GUC that allows
sharding the database based on schemas when enabled.
* Refactor the logic that automatically creates Citus managed tables
* Refactor CreateSingleShardTable() to allow specifying colocation id
instead
* Add support for schema-based-sharding via a GUC
### What this PR is about:
Add **citus.enable_schema_based_sharding GUC** to enable schema-based
sharding. Each schema created while this GUC is ON will be considered
as a tenant schema. Later on, regardless of whether the GUC is ON or
OFF, any table created in a tenant schema will be converted to a
single shard distributed table (without a shard key). All the tenant
tables that belong to a particular schema will be co-located with each
other and will have a shard count of 1.
We introduce a new metadata table --pg_dist_tenant_schema-- to do the
bookkeeping for tenant schemas:
```sql
psql> \d pg_dist_tenant_schema
Table "pg_catalog.pg_dist_tenant_schema"
┌───────────────┬─────────┬───────────┬──────────┬─────────┐
│ Column │ Type │ Collation │ Nullable │ Default │
├───────────────┼─────────┼───────────┼──────────┼─────────┤
│ schemaid │ oid │ │ not null │ │
│ colocationid │ integer │ │ not null │ │
└───────────────┴─────────┴───────────┴──────────┴─────────┘
Indexes:
"pg_dist_tenant_schema_pkey" PRIMARY KEY, btree (schemaid)
"pg_dist_tenant_schema_unique_colocationid_index" UNIQUE, btree (colocationid)
psql> table pg_dist_tenant_schema;
┌───────────┬───────────────┐
│ schemaid │ colocationid │
├───────────┼───────────────┤
│ 41963 │ 91 │
│ 41962 │ 90 │
└───────────┴───────────────┘
(2 rows)
```
Colocation id column of pg_dist_tenant_schema can never be NULL even
for the tenant schemas that don't have a tenant table yet. This is
because, we assign colocation ids to tenant schemas as soon as they
are created. That way, we can keep associating tenant schemas with
particular colocation groups even if all the tenant tables of a tenant
schema are dropped and recreated later on.
When a tenant schema is dropped, we delete the corresponding row from
pg_dist_tenant_schema. In that case, we delete the corresponding
colocation group from pg_dist_colocation as well.
### Future work for 12.0 release:
We're building schema-based sharding on top of the infrastructure that
adds support for creating distributed tables without a shard key
(https://github.com/citusdata/citus/pull/6867).
However, not all the operations that can be done on distributed tables
without a shard key necessarily make sense (in the same way) in the
context of schema-based sharding. For example, we need to think about
what happens if user attempts altering schema of a tenant table. We
will tackle such scenarios in a future PR.
We will also add a new UDF --citus.schema_tenant_set() or such-- to
allow users to use an existing schema as a tenant schema, and another
one --citus.schema_tenant_unset() or such-- to stop using a schema as
a tenant schema in future PRs.
Citus upgrade tests require some additional logic to run, because we
have a before and after schedule and we need to swap the Citus
version in-between. This adds that logic to `run_test.py`.
In passing this makes running upgrade tests locally multiple times
faster by caching tarballs.
DESCRIPTION: Fixes a crash when explain analyze is requested for a query
that is normally locally executed.
When explain analyze is requested for a query, a task with two queries
is created. Those two queries are
1. Wrapped Query --> `SELECT ... FROM
worker_save_query_explain_analyze(<query>, <explain analyze options>)`
2. Fetch Query -->` SELECT explain_analyze_output, execution_duration
FROM worker_last_saved_explain_analyze();`
When the query is locally executed a task with multiple queries causes a
crash in production. See the Assert at
57455dc64d/src/backend/distributed/executor/tuple_destination.c#:~:text=Assert(task%2D%3EqueryCount%20%3D%3D%201)%3B
This becomes a critical issue when auto_explain extension is used. When
auto_explain extension is enabled, explain analyze is automatically
requested for every query.
One possible solution could be not to create two queries for a locally
executed query. The fetch part may not have to be a query since the
values are available in local variables.
Until we enable local execution for explain analyze, it is best to
disable local execution.
Fixes#6777.
DESCRIPTION: Fixes a bug in background shard rebalancer where the
replicate reference tables task fails if the current user is not a
superuser.
This change is to be backported to earlier releases. We should fix the
permissions for replicate_reference_tables on main branch such that it
can be run by non-superuser roles.
Fixes#6925.
Fixes#6926.
We mark objects as distributed objects in Citus metadata only if we need
to propagate given the command that creates it to worker nodes. For this
reason, we were not doing this for the objects that are created while
pg_dist_node is empty.
One implication of doing so is that we defer the schema propagation to
the time when user creates the first distributed table in the schema.
However, this doesn't help for schema-based sharding (#6866) because we
want to sync pg_dist_tenant_schema to the worker nodes even for empty
schemas too.
* Support test dependencies for isolation tests without a schedule
* Comment out a test due to a known issue (#6901)
* Also, reduce the verbosity for some log messages and make some
tests compatible with run_test.py.
With this PR, we allow creating distributed tables with without
specifying a shard key via create_distributed_table(). Here are the
the important details about those tables:
* Specifying `shard_count` is not allowed because it is assumed to be 1.
* We mostly call such tables as "null shard-key" table in code /
comments.
* To avoid doing a breaking layout change in create_distributed_table();
instead of throwing an error, it will inform the user that
`distribution_type`
param is ignored unless it's explicitly set to NULL or 'h'.
* `colocate_with` param allows colocating such null shard-key tables to
each other.
* We define this table type, i.e., NULL_SHARD_KEY_TABLE, as a subclass
of
DISTRIBUTED_TABLE because we mostly want to treat them as distributed
tables in terms of SQL / DDL / operation support.
* Metadata for such tables look like:
- distribution method => DISTRIBUTE_BY_NONE
- replication model => REPLICATION_MODEL_STREAMING
- colocation id => **!=** INVALID_COLOCATION_ID (distinguishes from
Citus local tables)
* We assign colocation groups for such tables to different nodes in a
round-robin fashion based on the modulo of "colocation id".
Note that this PR doesn't care about DDL (except CREATE TABLE) / SQL /
operation (i.e., Citus UDFs) support for such tables but adds a
preliminary
API.
There was a bug related to regex. We sometimes caught the wrong line
when the test name is also included in comments.
Example: We caught the wrong line as multi_metadata_sync is included in
the comment before the test line.
```
# ----------
# multi_metadata_sync tests the propagation of mx-related metadata changes to metadata workers
# multi_unsupported_worker_operations tests that unsupported operations error out on metadata workers
# ----------
test: multi_metadata_sync
```
Solution: Restrict regex rule better.
In #6814 we started using the Python test runner for upgrade tests in
run_test.py, instead of the Perl based one. This had a problem though,
not all tests in minimal_schedule can be run with the Python runner.
This adds a separate minimal schedule for the pg_upgrade tests which
doesn't include the tests that break with the Python runner.
This PR also fixes various other issues that came up while testing
the upgrade tests.
DESCRIPTION: Changes the regression test setups adding the coordinator
to metadata by default.
When creating a Citus cluster, coordinator can be added in metadata
explicitly by running `citus_set_coordinator_host ` function. Adding the
coordinator to metadata allows to create citus managed local tables.
Other Citus functionality is expected to be unaffected.
This change adds the coordinator to metadata by default when creating
test clusters in regression tests.
There are 3 ways to run commands in a sql file (or a schedule which is a
sequence of sql files) with Citus regression tests. Below is how this PR
adds the coordinator to metadata for each.
1. `make <schedule_name>`
Changed the sql files (sql/multi_cluster_management.sql and
sql/minimal_cluster_management.sql) which sets up the test clusters such
that they call `citus_set_coordinator_host`. This ensures any following
tests will have the coordinator in metadata by default.
2. `citus_tests/run_test.py <sql_file_name>`
Changed the python code that sets up the cluster to always call `
citus_set_coordinator_host`.
For the upgrade tests, a version check is included to make sure
`citus_set_coordinator_host` function is available for a given version.
3. ` make check-arbitrary-configs `
Changed the python code that sets up the cluster to always call
`citus_set_coordinator_host `.
#6864 will be used to track the remaining work which is to change the
tests where coordinator is added/removed as a node.
Over the last few months run_test.py got more and more complex. This
refactors the code in `run_test.py` to be better understandable. Mostly
this splits up separate pieces of logic into separate functions.
For some tests such as upgrade tests and arbitrary config tests we set
up the citus cluster using Python. This setup is slightly different from
the perl based setup script (`multi_regress.pl`). Most importantly it
uses replication factor 1 by default.
This changes our run_test.py script to be able to run a schedule using
python instead of `multi_regress.pl`, for the tests that require it.
For now arbitrary config tests are still not runnable with
`run_test.py`, but this brings us one step closer to being able to do
that.
Fixes#6804
Having as little Perl as possible in our repo seems a worthy goal. Sadly
Postgres its Perl based TAP infrastructure was the only way in which we
could
run tests that were hard to do using only SQL commands. This change adds
infrastructure to run such "application style tests" using python and
converts all our existing Perl TAP tests to this new infrastructure.
Some of the helper functions that are added in this PR are currently
unused. Most of these will be used by the CDC PR that depends on this.
Some others are there because they were needed by the PgBouncer test
framework that this is based on, and the functions seemed useful enough
to citus testing to keep.
The main features of the test suite are:
1. Application style tests using a programming language that our
developers know how to write.
2. Caching of Citus clusters in-between tests using the ["fixture"
pattern][fixture] from `pytest` to achieve speedy tests. To make this
work in practice any changes made during a test are automatically
undone. Schemas, replication slots, subscriptions, publications are
dropped at the end of each test. And any changes made by `ALTER SYSTEM`
or manually editing of `pg_hba.conf` are undone too.
3. Automatic parallel execution of tests using the `-n auto` flag that's
added by `pytest-xdist`. This improved the speed of tests greatly with
the similar test framework I created for PgBouncer. Right now it doesn't
help much yet though, since this PR only adds two tests (one of which
takes ~10 times longer than the other).
Possible future improvements are:
1. Clean up even more things at the end of each test (e.g. users that
were created). These are fairly easy to add, but I have not done so yet
since they were not needed yet for this PR or the CDC PR. So I would not
be able to test the cleanup easily.
2. Support for query block detection similar to what we can now do using
isolation tests.
[fixture]: https://docs.pytest.org/en/6.2.x/fixture.html
DESCRIPTION: This PR removes the task dependencies between shard moves
for which the shards belong to different colocation groups. This change
results in scheduling multiple tasks in the RUNNABLE state. Therefore it
is possible that the background task monitor can run them concurrently.
Previously, all the shard moves planned in a rebalance operation took
dependency on each other sequentially.
For instance, given the following table and shards
colocation group 1 colocation group 2
table1 table2 table3 table4 table 5
shard11 shard21 shard31 shard41 shard51
shard12 shard22 shard32 shard42 shard52
if the rebalancer planner returned the below set of moves
` {move(shard11), move(shard12), move(shard41), move(shard42)}`
background rebalancer scheduled them such that they depend on each other
sequentially.
```
{move(reftables) if there is any, none}
|
move( shard11)
|
move(shard12)
| {move(shard41)<--- move(shard12)} This is an artificial dependency
move(shard41)
|
move(shard42)
```
This results in artificial dependencies between otherwise independent
moves.
Considering that the shards in different colocation groups can be moved
concurrently, this PR changes the dependency relationship between the
moves as follows:
```
{move(reftables) if there is any, none} {move(reftables) if there is any, none}
| |
move(shard11) move(shard41)
| |
move(shard12) move(shard42)
```
---------
Co-authored-by: Jelte Fennema <jelte.fennema@microsoft.com>
Description:
Implementing CDC changes using Logical Replication to avoid
re-publishing events multiple times by setting up replication origin
session, which will add "DoNotReplicateId" to every WAL entry.
- shard splits
- shard moves
- create distributed table
- undistribute table
- alter distributed tables (for some cases)
- reference table operations
The citus decoder which will be decoding WAL events for CDC clients,
ignores any WAL entry with replication origin that is not zero.
It also maps the shard names to distributed table names.
Soon I will be doing some changes related to #692 in router planner
and those changes require updating ~5/6 tests related to router
planning. And to make those test files runnable by run_test.py
multiple times, we need to make some other tests (that they're
run in parallel / they badly depend on) ready for run_test.py too.
When run_test.py is run for an upgrade_.*_after.sql then, then
automatically run the corresponding uprade_.*_before.sql file first.
This is because all those upgrade_.*_after.sql files depend on the
objects created in upgrade_.*_before.sql files by definition.
DESCRIPTION: Correctly report shard size in citus_shards view
When looking at citus_shards, people are interested in the actual size
that all the data related to the shard takes up on disk.
`pg_total_relation_size` is the function to use for that purpose. The
previously used `pg_relation_size` does not include indexes or TOAST.
Especially the missing toast can have enormous impact on the size of the
shown data.
Colm
Muhammad Usama
eaydingol
Onur Tirtir
Cédric Villemain
Naisila Puka
Jelte Fennema-Nio
Karina
Cédric Villemain
Gürkan İndibay
aykut-bozkurt
Emel Şimşek
Ahmet Gedemenli
rajeshkt78