Horton

Re: Add SPLIT PARTITION/MERGE PARTITIONS commands

jian he <jian.universality@gmail.com>

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From: jian he <jian.universality@gmail.com>
To: Dmitry Koval <d.koval@postgrespro.ru>
Cc: Alexander Korotkov <aekorotkov@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-08-21T06:45:12Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Adjust errcode in checkPartition()

  2. Fix usage of palloc() in MERGE/SPLIT PARTITION(s) code

  3. Implement ALTER TABLE ... SPLIT PARTITION ... command

  4. Implement ALTER TABLE ... MERGE PARTITIONS ... command

  5. Calculate agglevelsup correctly when Aggref contains a CTE.

  6. Use PqMsg_* macros in applyparallelworker.c.

  7. Restrict psql meta-commands in plain-text dumps.

  8. Ensure we have a snapshot when updating various system catalogs.

  9. Use specific collation where needed in new test

  10. Expand virtual generated columns in the planner

  11. Virtual generated columns

  12. Define PG_LOGICAL_DIR for path pg_logical/ in data folder

  13. Revert support for ALTER TABLE ... MERGE/SPLIT PARTITION(S) commands

  14. Avoid repeated table name lookups in createPartitionTable()

  15. Provide deterministic order for catalog queries in partition_split.sql

  16. Don't copy extended statistics during MERGE/SPLIT partition operations

  17. Fix the name collision detection in MERGE/SPLIT partition operations

  18. Fix regression tests conflict in 3ca43dbbb6

  19. Add permission check for MERGE/SPLIT partition operations

  20. Fix one more portability shortcoming in new test_pg_dump test.

  21. Inherit parent's AM for partition MERGE/SPLIT operations

  22. Add tab completion for partition MERGE/SPLIT operations

  23. Rename tables in tests of partition MERGE/SPLIT operations

  24. Make new partitions with parent's persistence during MERGE/SPLIT

  25. Document the way partition MERGE/SPLIT operations create new partitions

  26. Change the way ATExecMergePartitions() handles the name collision

  27. Grammar fixes for split/merge partitions code

  28. Checks for ALTER TABLE ... SPLIT/MERGE PARTITIONS ... commands

  29. Fix some grammer errors from error messages and codes comments

  30. Support TZ and OF format codes in to_timestamp().

  31. Support identity columns in partitioned tables

  32. Fix indentation in twophase.c

  33. Fix corner-case planner failure for MERGE.

  34. Doc: fix documentation example for bytea hex output format.

  35. Avoid repeated name lookups during table and index DDL.

Attachments

On Thu, Aug 21, 2025 at 10:53 AM jian he <jian.universality@gmail.com> wrote:
>
> > this time, I only checked
> > v52-0001-Implement-ALTER-TABLE-.-MERGE-PARTITIONS-.-comma.patch
> >


hi.
we may need to change checkPartition.

+-- ERROR:  "sales_apr2022" is not a table
+ALTER TABLE sales_range MERGE PARTITIONS (sales_feb2022,
sales_mar2022, sales_apr2022) INTO sales_feb_mar_apr2022;
+ERROR:  "sales_apr2022" is not a table
+HINT:  ALTER TABLE ... MERGE PARTITIONS can only merge partitions
don't have sub-partitions

+ERROR:  "sales_apr2022" is not a table
the above error message seems not intuitive to me.
IMV, the error message pattern should be something like:
ERROR: can not merge relation \"%s\"  with other partitions
DETAIL:  "sales_apr2022" is not a table
HINT:  ALTER TABLE ... MERGE PARTITIONS can only merge partitions
don't have sub-partition


+/*
+ * checkPartition
+ * Check whether partRelOid is a leaf partition of the parent table (rel).
+ * Partition with OID partRelOid must be locked before function call.
+ */
+static void
+checkPartition(Relation rel, Oid partRelOid)
"Partition with OID partRelOid must be locked before function call."
we can remove this sentence.
otherwise, "function call" seems confusing?


+SET search_path = pg_temp, partitions_merge_schema, public;
+
+BEGIN;
+CREATE TABLE t (i int) PARTITION BY RANGE (i);
+CREATE TABLE tp_0_1 PARTITION OF t FOR VALUES FROM (0) TO (1);
+CREATE TABLE tp_1_2 PARTITION OF t FOR VALUES FROM (1) TO (2);
+SELECT c.oid::pg_catalog.regclass, c.relpersistence FROM
pg_catalog.pg_class c WHERE c.oid = 't'::regclass;
+EXECUTE get_partition_info('{t}');
+DEALLOCATE get_partition_info;
+SET search_path = partitions_merge_schema, pg_temp, public;
+
+-- Can't merge temporary partitions into a persistent partition
+ALTER TABLE t MERGE PARTITIONS (tp_0_1, tp_1_2) INTO tp_0_2;
+ROLLBACK;

"+-- Can't merge temporary partitions into a persistent partition"
means
+ALTER TABLE t MERGE PARTITIONS (tp_0_1, tp_1_2) INTO tp_0_2;
should error out, but it didn't.
then I found out:

+/*
+ * ALTER TABLE <name> MERGE PARTITIONS <partition-list> INTO <partition-name>
+ */
+static void
+ATExecMergePartitions(List **wqueue, AlteredTableInfo *tab, Relation rel,
+  PartitionCmd *cmd, AlterTableUtilityContext *context)
+{
....
+ /*
+ * Look up existing relation by new partition name, check we have
+ * permission to create there, lock it against concurrent drop, and mark
+ * stmt->relation as RELPERSISTENCE_TEMP if a temporary namespace is
+ * selected.
+ */
+ cmd->name->relpersistence = rel->rd_rel->relpersistence;
+ RangeVarGetAndCheckCreationNamespace(cmd->name, NoLock, &existingRelid);

``cmd->name->relpersistence`` will be adjusted in
RangeVarGetAndCheckCreationNamespace->RangeVarAdjustRelationPersistence.

+ cmd->name->relpersistence = rel->rd_rel->relpersistence;
seems wrong?
comments "stmt->relation" not sure what it refers to?


attached patch did following the changes:
* remove line  ``cmd->name->relpersistence = rel->rd_rel->relpersistence;``
* refactor relpersistence, temp schema related regress tests.