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In the executor, use an array of pointers to access the rangetable.

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Instead of doing a lot of list_nth() accesses to es_range_table,
create a flattened pointer array during executor startup and index
into that to get at individual RangeTblEntrys.

This eliminates one source of O(N^2) behavior with lots of partitions.
(I'm not exactly convinced that it's the most important source, but
it's an easy one to fix.)

Amit Langote and David Rowley

Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp
This commit is contained in:
Tom Lane
2018-10-04 15:48:17 -04:00
parent 9ddef36278
commit d73f4c74dd
11 changed files with 87 additions and 52 deletions
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49
src/backend/executor/execUtils.c
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@ -26,6 +26,8 @@
*
* ExecOpenScanRelation Common code for scan node init routines.
*
* ExecInitRangeTable Set up executor's range-table-related data.
*
* ExecGetRangeTableRelation Fetch Relation for a rangetable entry.
*
* executor_errposition Report syntactic position of an error.
@ -108,6 +110,8 @@ CreateExecutorState(void)
estate->es_snapshot = InvalidSnapshot; /* caller must initialize this */
estate->es_crosscheck_snapshot = InvalidSnapshot; /* no crosscheck */
estate->es_range_table = NIL;
estate->es_range_table_array = NULL;
estate->es_range_table_size = 0;
estate->es_relations = NULL;
estate->es_plannedstmt = NULL;
@ -670,6 +674,43 @@ ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags)
return rel;
}
/*
* ExecInitRangeTable
* Set up executor's range-table-related data
*
* We build an array from the range table list to allow faster lookup by RTI.
* (The es_range_table field is now somewhat redundant, but we keep it to
* avoid breaking external code unnecessarily.)
* This is also a convenient place to set up the parallel es_relations array.
*/
void
ExecInitRangeTable(EState *estate, List *rangeTable)
{
Index rti;
ListCell *lc;
/* Remember the range table List as-is */
estate->es_range_table = rangeTable;
/* Set up the equivalent array representation */
estate->es_range_table_size = list_length(rangeTable);
estate->es_range_table_array = (RangeTblEntry **)
palloc(estate->es_range_table_size * sizeof(RangeTblEntry *));
rti = 0;
foreach(lc, rangeTable)
{
estate->es_range_table_array[rti++] = lfirst_node(RangeTblEntry, lc);
}
/*
* Allocate an array to store an open Relation corresponding to each
* rangetable entry, and initialize entries to NULL. Relations are opened
* and stored here as needed.
*/
estate->es_relations = (Relation *)
palloc0(estate->es_range_table_size * sizeof(Relation));
}
/*
* ExecGetRangeTableRelation
* Open the Relation for a range table entry, if not already done
@ -681,13 +722,13 @@ ExecGetRangeTableRelation(EState *estate, Index rti)
{
Relation rel;
Assert(rti > 0 && rti <= list_length(estate->es_range_table));
Assert(rti > 0 && rti <= estate->es_range_table_size);
rel = estate->es_relations[rti - 1];
if (rel == NULL)
{
/* First time through, so open the relation */
RangeTblEntry *rte = rt_fetch(rti, estate->es_range_table);
RangeTblEntry *rte = exec_rt_fetch(rti, estate);
Assert(rte->rtekind == RTE_RELATION);
@ -876,7 +917,7 @@ ExecLockNonLeafAppendTables(List *partitioned_rels, EState *estate)
ListCell *l;
Index rti = lfirst_int(lc);
bool is_result_rel = false;
Oid relid = getrelid(rti, estate->es_range_table);
Oid relid = exec_rt_fetch(rti, estate)->relid;
/* If this is a result relation, already locked in InitPlan */
foreach(l, stmt->nonleafResultRelations)
@ -911,7 +952,7 @@ ExecLockNonLeafAppendTables(List *partitioned_rels, EState *estate)
else
lockmode = AccessShareLock;
Assert(lockmode == rt_fetch(rti, estate->es_range_table)->rellockmode);
Assert(lockmode == exec_rt_fetch(rti, estate)->rellockmode);
LockRelationOid(relid, lockmode);
}