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: 2025-08-20T09:22:47Z
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

hi.
this time, I only checked
v52-0001-Implement-ALTER-TABLE-.-MERGE-PARTITIONS-.-comma.patch

typedef struct PartitionCmd
{
    NodeTag        type;
    RangeVar   *name;            /* name of partition to attach/detach/merge */
    PartitionBoundSpec *bound;    /* FOR VALUES, if attaching */
    List       *partlist;        /* list of partitions, for MERGE PARTITION
                                 * command */
    bool        concurrent;
} PartitionCmd;
The field "partlist" comments are not very helpful, IMO.
I think the following is more descriptive.
/* list of partitions to be merged, used only in ALTER TABLE MERGE PARTITION */


+ /*
+ * Search DEFAULT partition in the list. Open and lock partitions
+ * before calculating the boundary for resulting partition, we also
+ * check for ownership along the way.  We need to use
+ * AccessExclusiveLock here, because these merged partitions will be
+ * detached then dropped in ATExecMergePartitions.
+ */
+ partOid = RangeVarGetRelidExtended(name,
+   AccessExclusiveLock,
+   false,
+   RangeVarCallbackOwnsRelation,
+   NULL);
here "false" should be "0"?


+ /* Ranges of partitions should not overlap. */
+ for (i = 1; i < nparts; i++)
+ {
+ int index = lower_bounds[i]->index;
+ int prev_index = lower_bounds[i - 1]->index;
+ check_two_partitions_bounds_range(parent,
+  (RangeVar *) list_nth(partNames, prev_index),
+  (PartitionBoundSpec *) list_nth(bounds, prev_index),
+  (RangeVar *) list_nth(partNames, index),
+  (PartitionBoundSpec *) list_nth(bounds, index),
+  pstate);
+ }
the comment should be
+ /* Ranges of partitions should be adjacent */


--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -102,11 +102,11 @@ static ObjectAddress AddNewRelationType(const
char *typeName,
  Oid new_row_type,
  Oid new_array_type);
 static void RelationRemoveInheritance(Oid relid);
+static void StoreConstraints(Relation rel, List *cooked_constraints,
+ bool is_internal);
-static void StoreConstraints(Relation rel, List *cooked_constraints,
- bool is_internal);

Is this change necessary?


in  createPartitionTable
+ /* Create the relation. */
+ newRelId = heap_create_with_catalog(newPartName->relname,
+ namespaceId,
+ parent_rel->rd_rel->reltablespace,
....
+ newPartName->relpersistence,
....
+
+ /*
+ * We intended to create the partition with the same persistence as the
+ * parent table, but we still need to recheck because that might be
+ * affected by the search_path.  If the parent is permanent, so must be
+ * all of its partitions.
+ */
+ if (parent_rel->rd_rel->relpersistence != RELPERSISTENCE_TEMP &&
+ newRel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
+ ereport(ERROR,
+ errcode(ERRCODE_WRONG_OBJECT_TYPE),
+ errmsg("cannot create a temporary relation as partition of permanent
relation \"%s\"",
+   RelationGetRelationName(parent_rel)));
+
+ /* Permanent rels cannot be partitions belonging to temporary parent */
+ if (newRel->rd_rel->relpersistence != RELPERSISTENCE_TEMP &&
+ parent_rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
+ ereport(ERROR,
+ errcode(ERRCODE_WRONG_OBJECT_TYPE),
+ errmsg("cannot create a permanent relation as partition of temporary
relation \"%s\"",
+   RelationGetRelationName(parent_rel)));

i raised this question in [1], you replied at [2].
I still think it's not intuitive.
parent->relpersistence is fixed. and newRel->relpersistence is the same as
the same as newPartName->relpersistence, see heap_create_with_catalog.
These relpersistence error checks can happen before heap_create_with_catalog.

I added a regress test for src/test/modules/test_ddl_deparse.
I refactored regress to make
src/test/regress/expected/partition_merge.out less verbose.

[1]  https://postgr.es/m/CACJufxHM0sD8opy2hUxXLcdY3CQOCaMfsQtJs7yF3TS2YxSqKg@mail.gmail.com
[2] https://postgr.es/m/195b67ee-ef41-4451-9396-844442eef1a4@postgrespro.ru