**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: Fixes potential memory corruptions that could happen when
accessing pg_dist_object after a Citus downgrade is followed by a Citus
upgrade.
In case of Citus downgrade and further upgrade an undefined behavior may
be encountered. The reason is that Citus hardcoded the number of columns
in the extension's tables, but in case of downgrade and following update
some of these tables can have more columns, and some of them can be
marked as dropped.
This PR fixes all such tables using the approach introduced in #7950,
which solved the problem for the pg_dist_partition table.
See #7515 for a more thorough explanation.
---------
Co-authored-by: Karina Litskevich <litskevichkarina@gmail.com>
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
Enhance security by addressing a code scanning alert and refactoring the
background worker setup code for better maintainability and clarity.
---------
Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>
DESCRIPTION: Fixes potential memory corruptions that could happen when a
Citus downgrade is followed by a Citus upgrade.
In case of citus downgrade and further upgrade citus crash with core
dump.
The reason is that citus hardcoded number of columns in
pg_dist_partition table,
but in case of downgrade and following update table can have more
columns, and
some of then can be marked as dropped.
Patch suggest decision for this problem with using
tupleDescriptor->nattrs(postgres internal approach).
Fixes#7933.
---------
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
DESCRIPTION: Drops PG14 support
1. Remove "$version_num" != 'xx' from configure file
2. delete all PG_VERSION_NUM = PG_VERSION_XX references in the code
3. Look at pg_version_compat.h file, remove all _compat functions etc
defined specifically for PGXX differences
4. delete all PG_VERSION_NUM >= PG_VERSION_(XX+1), PG_VERSION_NUM <
PG_VERSION_(XX+1) ifs in the codebase
5. delete ruleutils_xx.c file
6. cleanup normalize.sed file from pg14 specific lines
7. delete all alternative output files for that particular PG version,
server_version_ge variable helps here
This is prep work for successful compilation with PG17
PG17added foreach_ptr, foreach_int and foreach_oid macros
Relevant PG commit
14dd0f27d7cd56ffae9ecdbe324965073d01a9ff
14dd0f27d7
We already have these macros, but they are different with the
PG17 ones because our macros take a DECLARED variable, whereas
the PG16 macros declare a locally-scoped loop variable themselves.
Hence I am renaming our macros to foreach_declared_
I am separating this into its own PR since it touches many files. The
main compilation PR is https://github.com/citusdata/citus/pull/7699
DESCRIPTION: Fix performance issue when creating distributed tables if
many already exist
This builds on the work to speed up EnsureSequenceTypeSupported, and now
does something similar for SequenceUsedInDistributedTable.
SequenceUsedInDistributedTable had a similar O(number of citus tables)
operation. This fixes that and speeds up creation of distributed tables
significantly when many distributed tables already exist.
Fixes#7022
DESCRIPTION: Fix performance issue when creating distributed tables and many already exist
EnsureSequenceTypeSupported was doing an O(number of distributed tables)
operation. This can become very slow with lots of Citus tables, which
now happens much more frequently in practice due to schema based sharding.
Partially addresses #7022
Moves the following functions to the Citus internal schema:
citus_internal_local_blocked_processes
citus_internal_global_blocked_processes
citus_internal_mark_node_not_synced
citus_internal_unregister_tenant_schema_globally
citus_internal_update_none_dist_table_metadata
citus_internal_update_placement_metadata
citus_internal_update_relation_colocation
citus_internal_start_replication_origin_tracking
citus_internal_stop_replication_origin_tracking
citus_internal_is_replication_origin_tracking_active
#7405
---------
Co-authored-by: Jelte Fennema-Nio <jelte.fennema@microsoft.com>
Moves the following functions:
citus_internal_delete_colocation_metadata
citus_internal_delete_partition_metadata
citus_internal_delete_placement_metadata
citus_internal_delete_shard_metadata
citus_internal_delete_tenant_schema
Move more functions to citus_internal schema, the list:
citus_internal_add_placement_metadata
citus_internal_add_shard_metadata
citus_internal_add_tenant_schema
citus_internal_adjust_local_clock_to_remote
citus_internal_database_command
#7405
Move citus_internal_acquire_citus_advisory_object_class_lock and
citus_internal_add_colocation_metadata functions from pg_catalog to
citus_internal.
#7405
DESCRIPTION: Adds support for 2PC from non-Citus main databases
This PR only adds support for `CREATE USER` queries, other queries need
to be added. But it should be simple because this PR creates the
underlying structure.
Citus main database is the database where the Citus extension is
created. A non-main database is all the other databases that are in the
same node with a Citus main database.
When a `CREATE USER` query is run on a non-main database we:
1. Run `start_management_transaction` on the main database. This
function saves the outer transaction's xid (the non-main database
query's transaction id) and marks the current query as main db command.
2. Run `execute_command_on_remote_nodes_as_user("CREATE USER
<username>", <username to run the command>)` on the main database. This
function creates the users in the rest of the cluster by running the
query on the other nodes. The user on the current node is created by the
query on the outer, non-main db, query to make sure consequent commands
in the same transaction can see this user.
3. Run `mark_object_distributed` on the main database. This function
adds the user to `pg_dist_object` in all of the nodes, including the
current one.
This PR also implements transaction recovery for the queries from
non-main databases.
This change adds a script to programatically group all includes in a
specific order. The script was used as a one time invocation to group
and sort all includes throught our formatted code. The grouping is as
follows:
- System includes (eg. `#include<...>`)
- Postgres.h (eg. `#include "postgres.h"`)
- Toplevel imports from postgres, not contained in a directory (eg.
`#include "miscadmin.h"`)
- General postgres includes (eg . `#include "nodes/..."`)
- Toplevel citus includes, not contained in a directory (eg. `#include
"citus_verion.h"`)
- Columnar includes (eg. `#include "columnar/..."`)
- Distributed includes (eg. `#include "distributed/..."`)
Because it is quite hard to understand the difference between toplevel
citus includes and toplevel postgres includes it hardcodes the list of
toplevel citus includes. In the same manner it assumes anything not
prefixed with `columnar/` or `distributed/` as a postgres include.
The sorting/grouping is enforced by CI. Since we do so with our own
script there are not changes required in our uncrustify configuration.
DESCRIPTION: Adds support for propagating `CREATE`/`DROP` database
In this PR, create and drop database support is added.
For CREATE DATABASE:
* "oid" option is not supported
* specifying "strategy" to be different than "wal_log" is not supported
* specifying "template" to be different than "template1" is not
supported
The last two are because those are not saved in `pg_database` and when
activating a node, we cannot assume what parameters were provided when
creating the database.
And "oid" is not supported because whether user specified an arbitrary
oid when creating the database is not saved in pg_database and we want
to avoid from oid collisions that might arise from attempting to use an
auto-assigned oid on workers.
Finally, in case of node activation, GRANTs for the database are also
propagated.
---------
Co-authored-by: Jelte Fennema-Nio <github-tech@jeltef.nl>
Co-authored-by: Jelte Fennema-Nio <jelte.fennema@microsoft.com>
Co-authored-by: Onur Tirtir <onurcantirtir@gmail.com>
DESCRIPTION: Adds support from issuing role management commands from worker nodes
It's unlikely to get into a distributed deadlock with role commands, we
don't care much about them at the moment.
There were several attempts to reduce the chances of a deadlock but we
didn't any of them merged into main branch yet, see:
#7325#7016#7009
Index scans in PG16 return empty sets because of extra compatibility
enforcement for `ScanKeyInit` arguments.
Could be one of the relevant PG commits:
c8b2ef05f4
This PR fixes all incompatible `RegProcedure` and `Datum` arguments in
all `ScanKeyInit` functions used throughout the codebase.
Helpful for https://github.com/citusdata/citus/pull/6952
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
Adds Support for Single Shard Tables in
`update_distributed_table_colocation`.
This PR changes checks that make sure tables should be hash distributed
table to hash or single shard distributed tables.
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.
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.
We need to break sequence dependency for a table while creating the
table during non-transactional metadata sync to ensure idempotency of
the creation of the table.
**Problem:**
When we send `SELECT
pg_catalog.worker_drop_sequence_dependency(logicalrelid::regclass::text)
FROM pg_dist_partition` to workers during the non-transactional sync,
table might not be in `pg_dist_partition` at worker, and sequence
dependency is not broken at the worker.
**Solution:**
We break sequence dependency via `SELECT
pg_catalog.worker_drop_sequence_dependency(logicalrelid::regclass::text)`
for each table while creating it at the workers. It is safe to send
since the udf is a no-op when there is no sequence dependency.
DESCRIPTION: Fixes a bug related to sequence idempotency at
non-transactional sync.
Fixes https://github.com/citusdata/citus/issues/6888.
Add new metadata sync methods which uses MemorySyncContext api so that during the sync we can
- free memory to prevent OOM,
- use either transactional or nontransactional modes according to the GUC .
- Create MetadataSyncContext api to encapsulate
both transactional and nontransactional modes,
- Add a GUC to switch between metadata sync transaction modes.
This pull request proposes a change to the logic used for propagating
identity columns to worker nodes in citus. Instead of creating a
dependent sequence for each identity column and changing its default
value to `nextval(seq)/worker_nextval(seq)`, this update will pass the
identity columns as-is to the worker nodes.
Please note that there are a few limitations to this change.
1. Only bigint identity columns will be allowed in distributed tables to
ensure compatibility with the DDL from any node functionality. Our
current distributed sequence implementation only allows insert
statements from all nodes for bigint sequences.
2. `alter_distributed_table` and `undistribute_table` operations will
not be allowed for tables with identity columns. This is because we do
not have a proper way of keeping sequence states consistent across the
cluster.
DESCRIPTION: Prevents using identity columns on data types other than
`bigint` on distributed tables
DESCRIPTION: Prevents using `alter_distributed_table` and
`undistribute_table` UDFs when a table has identity columns
DESCRIPTION: Fixes a bug that prevents enforcing identity column
restrictions on worker nodes
Depends on #6740Fixes#6694
Now that we will soon add another table type having DISTRIBUTE_BY_NONE
as distribution method and that we want the code to interpret such
tables mostly as distributed tables, let's make the definition of those
other two table types more strict by removing
CITUS_TABLE_WITH_NO_DIST_KEY
macro.
And instead, use HasDistributionKey() check in the places where the
logic applies to all table types that have / don't have a distribution
key. In future PRs, we might want to convert some of those
HasDistributionKey() checks if logic only applies to Citus local /
reference tables, not the others.
And adding HasDistributionKey() also allows us to consider having
DISTRIBUTE_BY_NONE as the distribution method as a "table attribute"
that can apply to distributed tables too, rather something that
determines the table type.
DESCRIPTION: Drop `SHARD_STATE_TO_DELETE` and use the cleanup records
instead
Drops the shard state that is used to mark shards as orphaned. Now we
insert cleanup records into `pg_dist_cleanup` so "orphaned" shards will
be dropped either by maintenance daemon or internal cleanup calls. With
this PR, we make the "cleanup orphaned shards" functions to be no-op, as
they would not be needed anymore.
This PR includes some naming changes about placement functions. We don't
need functions that filter orphaned shards, as there will be no orphaned
shards anymore.
We will also be introducing a small script with this PR, for users with
orphaned shards. We'll basically delete the orphaned shard entries from
`pg_dist_placement` and insert cleanup records into `pg_dist_cleanup`
for each one of them, during Citus upgrade.
We also have a lot of flakiness fixes in this PR.
Co-authored-by: Jelte Fennema <github-tech@jeltef.nl>
Added create_distributed_table_concurrently which is nonblocking variant of create_distributed_table.
It bases on the split API which takes advantage of logical replication to support nonblocking split operations.
Co-authored-by: Marco Slot <marco.slot@gmail.com>
Co-authored-by: aykutbozkurt <aykut.bozkurt1995@gmail.com>
There are 3 different ways that a sequence can be interacting
with tables. (1) and (2) are already supported. This commit adds
support for (3).
(1) column DEFAULT nextval('seq'):
The dependency is roughly like below,
and ExpandCitusSupportedTypes() is responsible
for finding the depending sequences.
schema <--- table <--- column <---- default value
^ |
|------------------ sequence <--------|
(2) serial columns: Bigserial/small serial etc:
The dependency is roughly like below,
and ExpandCitusSupportedTypes() is responsible
for finding the depending sequences.
schema <--- table <--- column <---- default value
^ |
| |
sequence <--------|
(3) Sequence OWNED BY table.column: Added support for
this type of resolution in this commit.
The dependency is almost like the following, and
ExpandCitusSupportedTypes() is NOT responsible for finding
the dependency.
schema <--- table <--- column
^
|
sequence
* Remove if conditions with PG_VERSION_NUM < 13
* Remove server_above_twelve(&eleven) checks from tests
* Fix tests
* Remove pg12 and pg11 alternative test output files
* Remove pg12 specific normalization rules
* Some more if conditions in the code
* Change RemoteCollationIdExpression and some pg12/pg13 comments
* Remove some more normalization rules
Muhammad Usama
Karina
ibrahim halatci
manaldush
Naisila Puka
michailtoksovo
Jelte Fennema-Nio
Hanefi Onaldi
eaydingol
Halil Ozan Akgül
Nils Dijk
Gürkan İndibay
Onur Tirtir
aykut-bozkurt
aykutbozkurt
Gokhan Gulbiz
Marco Slot
Ahmet Gedemenli
Marco Slot
Önder Kalacı