Horton

Re: Add SPLIT PARTITION/MERGE PARTITIONS commands

jian he <jian.universality@gmail.com>

View thread
From: jian he <jian.universality@gmail.com>
To: Dmitry Koval <d.koval@postgrespro.ru>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2025-07-16T11:42:38Z
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

bug:

begin;
drop table if exists pks cascade;
create table pks(i int primary key, b int) partition by range (i);
create table pks_34 partition of pks for values from (3) to (6);
create table pks_d partition of pks default;
insert into pks values (0), (1), (3), (4), (5);
commit;
alter table pks_d add constraint cc check(i <> 5);
ALTER TABLE pks SPLIT PARTITION pks_34 INTO
    (PARTITION pks_3 FOR VALUES FROM (3) TO (4),
      PARTITION pks_4 FOR VALUES FROM (4) TO (5));

now pks_d have values(5) for column i, which would violate the
cc check constraint.
------------------------
/*
 * PartitionCmd - info for ALTER TABLE/INDEX ATTACH/DETACH PARTITION commands
 */
typedef struct PartitionCmd
{
    NodeTag        type;
    RangeVar   *name;            /* name of partition to
attach/detach/merge/split */
    PartitionBoundSpec *bound;    /* FOR VALUES, if attaching */
    List       *partlist;        /* list of partitions, for MERGE/SPLIT
                                 * PARTITION command */
    bool        concurrent;
} PartitionCmd;
"ALTER TABLE/INDEX ATTACH/DETACH PARTITION" comments need updated.


SplitPartitionMoveRows
                ereport(ERROR,
                        errcode(ERRCODE_CHECK_VIOLATION),
                        errmsg("can not find partition for split
partition row"),
                        errtable(splitRel));
will this ever be reachable?

in SplitPartitionMoveRows
+ if (sps->bound->is_default)
+ {
+ /* We should not create constraint for detached DEFAULT partition. */
+ defaultPartCtx = pc;
+ }
I am not sure the comment "detached DEFAULT partition" is correct.
the "constraint" is not ideal, better word would be "partition
constraint" or "partition qual".

In ATExecSplitPartition,
we can first create the new partitions and then detach the original partition.
It makes more sense, IMHO.
For example:
ALTER TABLE pks SPLIT PARTITION pks_34 INTO
    (PARTITION pks_3 FOR VALUES FROM (3) TO (4),
     PARTITION pks_4 FOR VALUES FROM (4) TO (6));
In this case, we could first create the relations pks_3 and pks_4, then detach
the partition pks_34

should the newly created partitions be based on the split partition or on the
partitioned table?
In the current v50 implementation, they are based on the partitioned table, but
these newly created partitions based on the split partition also make sense.


+ econtext->ecxt_scantuple = srcslot;
+
+ /* Search partition for current slot srcslot. */
+ foreach(listptr, partContexts)
+ {
+ pc = (SplitPartitionContext *) lfirst(listptr);
+
+ if (pc->partqualstate /* skip DEFAULT partition */ &&
+ ExecCheck(pc->partqualstate, econtext))
+ {
+ found = true;
+ break;
+ }
+ ResetExprContext(econtext);
this ResetExprContext is not needed, if you are evaluate different
ExprState again the same slot. See ExecRelCheck also.


see execute_extension_script
                     control->trusted
                     ? errhint("Must have CREATE privilege on current
database to create this extension.")
                     : errhint("Must be superuser to create this extension.")));
in v50-0002, we can refactor it as like the following
checkPartition(Relation rel, Oid partRelOid, bool is_merge)
{
    Relation    partRel;
    partRel = table_open(partRelOid, NoLock);
    if (partRel->rd_rel->relkind != RELKIND_RELATION)
        ereport(ERROR,
                errcode(ERRCODE_WRONG_OBJECT_TYPE),
                errmsg("\"%s\" is not a table",
RelationGetRelationName(partRel)),
                is_merge
                ? errhint("ALTER TABLE ... MERGE PARTITIONS can only
merge partitions don't have sub-partitions")
                : errhint("ALTER TABLE ... SPLIT PARTITIONS can only
split partitions don't have sub-partitions"));

I did some regress test refactoring to reduce test size.
-SELECT * FROM sales_range;
+SELECT tableoid, * FROM sales_range ORDER BY salesperson_id;

other miscellaneous refactoring is also attached.