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Revert "Fix parallel-safety check of expressions and predicate for index builds" 

This reverts commit eae7be600b, following a discussion with Tom Lane,
due to concerns that this impacts the decisions made by the planner for
the number of workers spawned based on the inlining and const-folding of
index expressions and predicate for cases that would have worked until
this commit.

Discussion: https://postgr.es/m/162802.1709746091@sss.pgh.pa.us
Backpatch-through: 12
This commit is contained in:
Michael Paquier 2024-03-07 08:31:04 +09:00
parent 3b671dcf53
commit e82b64a92c
5 changed files with 2 additions and 121 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/backend/optimizer/plan/planner.c
View File

@ -6143,18 +6143,10 @@ plan_create_index_workers(Oid tableOid, Oid indexOid)
* Currently, parallel workers can't access the leader's temporary tables.
* Furthermore, any index predicate or index expressions must be parallel
* safe.
*
* Fetch the list of expressions and predicates directly from the
* catalogs. Retrieving this information from the relcache would cause
* the expressions and predicates to be flattened, losing properties that
* can be important to check if parallel workers can be used. For
* example, immutable parallel-unsafe functions, that cannot be used in
* parallel workers, would be changed to Const nodes, that are safe in
* parallel workers.
*/
if (heap->rd_rel->relpersistence == RELPERSISTENCE_TEMP ||
!is_parallel_safe(root, (Node *) get_index_expressions(indexOid)) ||
!is_parallel_safe(root, (Node *) get_index_predicate(indexOid)))
!is_parallel_safe(root, (Node *) RelationGetIndexExpressions(index)) ||
!is_parallel_safe(root, (Node *) RelationGetIndexPredicate(index)))
{
parallel_workers = 0;
goto done;

68
src/backend/utils/cache/lsyscache.c vendored
View File

@ -3510,74 +3510,6 @@ get_index_column_opclass(Oid index_oid, int attno)
return opclass;
}
/*
* get_index_expressions
*
* Given the index OID, its a List of its expressions or NIL if none.
*/
List *
get_index_expressions(Oid index_oid)
{
List *result;
HeapTuple tuple;
Datum exprDatum;
bool isnull;
char *exprString;
tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(index_oid));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for index %u", index_oid);
exprDatum = SysCacheGetAttr(INDEXRELID, tuple,
Anum_pg_index_indexprs, &isnull);
if (isnull)
{
ReleaseSysCache(tuple);
return NIL;
}
exprString = TextDatumGetCString(exprDatum);
result = (List *) stringToNode(exprString);
pfree(exprString);
ReleaseSysCache(tuple);
return result;
}
/*
* get_index_predicate
*
* Given the index OID, return a List of its predicate or NIL if none.
*/
List *
get_index_predicate(Oid index_oid)
{
List *result;
HeapTuple tuple;
Datum predDatum;
bool isnull;
char *predString;
tuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(index_oid));
if (!HeapTupleIsValid(tuple))
elog(ERROR, "cache lookup failed for index %u", index_oid);
predDatum = SysCacheGetAttr(INDEXRELID, tuple,
Anum_pg_index_indpred, &isnull);
if (isnull)
{
ReleaseSysCache(tuple);
return NIL;
}
predString = TextDatumGetCString(predDatum);
result = (List *) stringToNode(predString);
pfree(predString);
ReleaseSysCache(tuple);
return result;
}
/*
* get_index_isreplident
*

2
src/include/utils/lsyscache.h
View File

@ -195,8 +195,6 @@ extern Oid get_range_collation(Oid rangeOid);
extern Oid get_range_multirange(Oid rangeOid);
extern Oid get_multirange_range(Oid multirangeOid);
extern Oid get_index_column_opclass(Oid index_oid, int attno);
extern List *get_index_expressions(Oid index_oid);
extern List *get_index_predicate(Oid index_oid);
extern bool get_index_isreplident(Oid index_oid);
extern bool get_index_isvalid(Oid index_oid);
extern bool get_index_isclustered(Oid index_oid);

19
src/test/regress/expected/btree_index.out
View File

@ -387,22 +387,3 @@ ALTER INDEX btree_part_idx ALTER COLUMN id SET (n_distinct=100);
ERROR: ALTER action ALTER COLUMN ... SET cannot be performed on relation "btree_part_idx"
DETAIL: This operation is not supported for partitioned indexes.
DROP TABLE btree_part;
-- Test with index expression and predicate that include a parallel unsafe
-- function.
CREATE FUNCTION para_unsafe_f() RETURNS int IMMUTABLE PARALLEL UNSAFE
AS $$
BEGIN
RETURN 0;
EXCEPTION WHEN OTHERS THEN
RETURN 1;
END$$ LANGUAGE plpgsql;
CREATE TABLE btree_para_bld(i int);
ALTER TABLE btree_para_bld SET (parallel_workers = 4);
SET max_parallel_maintenance_workers TO 4;
-- With parallel-unsafe expression
CREATE INDEX ON btree_para_bld((i + para_unsafe_f()));
-- With parallel-unsafe predicate
CREATE INDEX ON btree_para_bld(i) WHERE i > para_unsafe_f();
RESET max_parallel_maintenance_workers;
DROP TABLE btree_para_bld;
DROP FUNCTION para_unsafe_f;

22
src/test/regress/sql/btree_index.sql
View File

@ -242,25 +242,3 @@ CREATE TABLE btree_part (id int4) PARTITION BY RANGE (id);
CREATE INDEX btree_part_idx ON btree_part(id);
ALTER INDEX btree_part_idx ALTER COLUMN id SET (n_distinct=100);
DROP TABLE btree_part;
-- Test with index expression and predicate that include a parallel unsafe
-- function.
CREATE FUNCTION para_unsafe_f() RETURNS int IMMUTABLE PARALLEL UNSAFE
AS $$
BEGIN
RETURN 0;
EXCEPTION WHEN OTHERS THEN
RETURN 1;
END$$ LANGUAGE plpgsql;
CREATE TABLE btree_para_bld(i int);
ALTER TABLE btree_para_bld SET (parallel_workers = 4);
SET max_parallel_maintenance_workers TO 4;
-- With parallel-unsafe expression
CREATE INDEX ON btree_para_bld((i + para_unsafe_f()));
-- With parallel-unsafe predicate
CREATE INDEX ON btree_para_bld(i) WHERE i > para_unsafe_f();
RESET max_parallel_maintenance_workers;
DROP TABLE btree_para_bld;
DROP FUNCTION para_unsafe_f;