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Make the conditions in IsIndexUsableForReplicaIdentityFull() more explicit

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IsIndexUsableForReplicaIdentityFull() described a number of conditions
that a suitable index has to fulfill.  But not all of these were
actually checked in the code.  Instead, it appeared to rely on
get_equal_strategy_number() to filter out any indexes that are not
btree or hash.  As we look to generalize index AM capabilities, this
would possibly break if we added additional support in
get_equal_strategy_number().  Instead, write out code to check for the
required capabilities explicitly.  This shouldn't change any behaviors
at the moment.

Reviewed-by: Paul Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com
This commit is contained in:
Peter Eisentraut 2024-12-10 13:11:34 +01:00
parent a2a475b011
commit 13544e790e
1 changed files with 25 additions and 27 deletions
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52
src/backend/replication/logical/relation.c
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@ -17,9 +17,7 @@
#include "postgres.h"
#ifdef USE_ASSERT_CHECKING
#include "access/amapi.h"
#endif
#include "access/genam.h"
#include "access/table.h"
#include "catalog/namespace.h"
@ -798,9 +796,10 @@ FindUsableIndexForReplicaIdentityFull(Relation localrel, AttrMap *attrmap)
/*
* Returns true if the index is usable for replica identity full.
*
* The index must be btree or hash, non-partial, and the leftmost field must be
* a column (not an expression) that references the remote relation column. These
* limitations help to keep the index scan similar to PK/RI index scans.
* The index must have an equal strategy for each key column, be non-partial,
* and the leftmost field must be a column (not an expression) that references
* the remote relation column. These limitations help to keep the index scan
* similar to PK/RI index scans.
*
* attrmap is a map of local attributes to remote ones. We can consult this
* map to check whether the local index attribute has a corresponding remote
@ -813,19 +812,6 @@ FindUsableIndexForReplicaIdentityFull(Relation localrel, AttrMap *attrmap)
* compare the tuples for non-PK/RI index scans. See
* RelationFindReplTupleByIndex().
*
* The reasons why only Btree and Hash indexes can be considered as usable are:
*
* 1) Other index access methods don't have a fixed strategy for equality
* operation. Refer get_equal_strategy_number().
*
* 2) For indexes other than PK and REPLICA IDENTITY, we need to match the
* local and remote tuples. The equality routine tuples_equal() cannot accept
* a datatype (e.g. point or box) that does not have a default operator class
* for Btree or Hash.
*
* XXX: Note that BRIN and GIN indexes do not implement "amgettuple" which
* will be used later to fetch the tuples. See RelationFindReplTupleByIndex().
*
* XXX: To support partial indexes, the required changes are likely to be larger.
* If none of the tuples satisfy the expression for the index scan, we fall-back
* to sequential execution, which might not be a good idea in some cases.
@ -853,6 +839,21 @@ IsIndexUsableForReplicaIdentityFull(Relation idxrel, AttrMap *attrmap)
return false;
}
/*
* For indexes other than PK and REPLICA IDENTITY, we need to match the
* local and remote tuples. The equality routine tuples_equal() cannot
* accept a data type where the type cache cannot provide an equality
* operator.
*/
for (int i = 0; i < idxrel->rd_att->natts; i++)
{
TypeCacheEntry *typentry;
typentry = lookup_type_cache(TupleDescAttr(idxrel->rd_att, i)->atttypid, TYPECACHE_EQ_OPR_FINFO);
if (!OidIsValid(typentry->eq_opr_finfo.fn_oid))
return false;
}
/* The leftmost index field must not be an expression */
keycol = idxrel->rd_index->indkey.values[0];
if (!AttributeNumberIsValid(keycol))
@ -867,15 +868,12 @@ IsIndexUsableForReplicaIdentityFull(Relation idxrel, AttrMap *attrmap)
attrmap->attnums[AttrNumberGetAttrOffset(keycol)] < 0)
return false;
#ifdef USE_ASSERT_CHECKING
{
IndexAmRoutine *amroutine;
/* The given index access method must implement amgettuple. */
amroutine = GetIndexAmRoutineByAmId(idxrel->rd_rel->relam, false);
Assert(amroutine->amgettuple != NULL);
}
#endif
/*
* The given index access method must implement "amgettuple", which will
* be used later to fetch the tuples. See RelationFindReplTupleByIndex().
*/
if (GetIndexAmRoutineByAmId(idxrel->rd_rel->relam, false)->amgettuple == NULL)
return false;
return true;
}