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Undo planner extended statistics override (#6492)

marcocitus/sync-via-executor
Önder Kalacı 2023-01-04 13:25:57 +01:00 committed by GitHub
parent a1aa96b32c
commit eb75decbeb
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1 changed files with 7 additions and 27 deletions
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34
src/backend/distributed/planner/distributed_planner.c
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@ -1940,37 +1940,17 @@ multi_relation_restriction_hook(PlannerInfo *root, RelOptInfo *relOptInfo,
{
cacheEntry = GetCitusTableCacheEntry(rte->relid);
#if PG_VERSION_NUM == PG_VERSION_15
/*
* The statistics objects of the distributed table are not relevant
* for the distributed planning, so we can override it.
* Postgres 15.0 had a bug regarding inherited statistics expressions,
* which is fixed in 15.1 via Postgres commit
* 1f1865e9083625239769c26f68b9c2861b8d4b1c.
*
* Normally, we should not need this. However, the combination of
* Postgres commit 269b532aef55a579ae02a3e8e8df14101570dfd9 and
* Citus function AdjustPartitioningForDistributedPlanning()
* forces us to do this. The commit expects statistics objects
* of partitions to have "inh" flag set properly. Whereas, the
* function overrides "inh" flag. To avoid Postgres to throw error,
* we override statlist such that Postgres does not try to process
* any statistics objects during the standard_planner() on the
* coordinator. In the end, we do not need the standard_planner()
* on the coordinator to generate an optimized plan. We call
* into standard_planner() for other purposes, such as generating the
* relationRestrictionContext here.
*
* AdjustPartitioningForDistributedPlanning() is a hack that we use
* to prevent Postgres' standard_planner() to expand all the partitions
* for the distributed planning when a distributed partitioned table
* is queried. It is required for both correctness and performance
* reasons. Although we can eliminate the use of the function for
* the correctness (e.g., make sure that rest of the planner can handle
* partitions), it's performance implication is hard to avoid. Certain
* planning logic of Citus (such as router or query pushdown) relies
* heavily on the relationRestrictionList. If
* AdjustPartitioningForDistributedPlanning() is removed, all the
* partitions show up in the, causing high planning times for
* such queries.
* Hence, we only set this value on exactly PG15.0
*/
relOptInfo->statlist = NIL;
#endif
relationRestrictionContext->allReferenceTables &=
IsCitusTableTypeCacheEntry(cacheEntry, REFERENCE_TABLE);