Horton

Re: generic plans and "initial" pruning

Alexander Law <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Amit Langote <amitlangote09@gmail.com>, Tomas Vondra <tomas@vondra.me>
Cc: Robert Haas <robertmhaas@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>, Daniel Gustafsson <daniel@yesql.se>, David Rowley <dgrowleyml@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Thom Brown <thom@linux.com>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2025-02-14T21:00:00Z
Lists: pgsql-hackers 
Hello Amit,

06.02.2025 04:35, Amit Langote wrote:
> I plan to push 0001 tomorrow, barring any objections.
>

Please try the following script:
CREATE TABLE pt (a int, b int) PARTITION BY range (a);
CREATE TABLE tp1 PARTITION OF pt FOR VALUES FROM (1) TO (2);
CREATE TABLE tp2 PARTITION OF pt FOR VALUES FROM (2) TO (3);

MERGE INTO pt
USING (SELECT pg_backend_pid() AS pid) AS q JOIN tp1 ON (q.pid = tp1.a)
ON pt.a = tp1.a
WHEN MATCHED THEN DELETE;

which fails for me with segfault:
Program terminated with signal SIGSEGV, Segmentation fault.
#0  ExecInitMerge (mtstate=0x5a9b9fbccae0, estate=0x5a9b9fbcbe20) at nodeModifyTable.c:3680
3680                    relationDesc = RelationGetDescr(resultRelInfo->ri_RelationDesc);
(gdb) bt
#0  ExecInitMerge (mtstate=0x5a9b9fbccae0, estate=0x5a9b9fbcbe20) at nodeModifyTable.c:3680
#1  0x00005a9b67e6dfb5 in ExecInitModifyTable (node=0x5a9b9fbd5858, estate=0x5a9b9fbcbe20, eflags=0) at 
nodeModifyTable.c:4906
#2  0x00005a9b67e273f7 in ExecInitNode (node=0x5a9b9fbd5858, estate=0x5a9b9fbcbe20, eflags=0) at execProcnode.c:177
#3  0x00005a9b67e1b9d2 in InitPlan (queryDesc=0x5a9b9fbb9970, eflags=0) at execMain.c:1092
#4  0x00005a9b67e1a524 in standard_ExecutorStart (queryDesc=0x5a9b9fbb9970, eflags=0) at execMain.c:268
#5  0x00005a9b67e1a223 in ExecutorStart (queryDesc=0x5a9b9fbb9970, eflags=0) at execMain.c:142
...

starting from cbc127917.

(I've discovered this anomaly with SQLsmith.)

Best regards,
Alexander Lakhin
Neon (https://neon.tech)

Commits

  1. Stamp 19beta1.

  2. Revert "Don't lock partitions pruned by initial pruning"

  3. Ensure first ModifyTable rel initialized if all are pruned

  4. Fix bug in cbc127917 to handle nested Append correctly

  5. Remove unstable test suite added by 525392d57

  6. Don't lock partitions pruned by initial pruning

  7. Fix an oversight in cbc127917 to handle MERGE correctly

  8. Track unpruned relids to avoid processing pruned relations

  9. Perform runtime initial pruning outside ExecInitNode()

  10. Move PartitionPruneInfo out of plan nodes into PlannedStmt

  11. Fix setrefs.c's failure to do expression processing on prune steps.

  12. Remove obsolete executor cleanup code

  13. Revert "Move PartitionPruneInfo out of plan nodes into PlannedStmt"

  14. Move PartitioPruneInfo out of plan nodes into PlannedStmt

  15. Refactor and cleanup runtime partition prune code a little

  16. Remove some unnecessary fields from Plan trees.

  17. Remove more redundant relation locking during executor startup.

  18. Shut down Gather's children before shutting down Gather itself.