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Reset, not recreate, execGrouping.c style hashtables.

Browse Source 
This uses the facility added in the preceding commit to fix
performance issues caused by rebuilding the hashtable (with its
comparator expression being the most expensive bit), after every
reset. That's especially important when the comparator is JIT
compiled.

Bug: #15592 #15486
Reported-By: Jakub Janeček, Dmitry Marakasov
Author: Andres Freund
Discussion:
    https://postgr.es/m/15486-05850f065da42931@postgresql.org
    https://postgr.es/m/20190114180423.ywhdg2iagzvh43we@alap3.anarazel.de
Backpatch: 11, where I broke this in bf6c614a2f
This commit is contained in:
Andres Freund
2019-02-09 00:35:57 -08:00
parent 317ffdfeaa
commit 356687bd82
4 changed files with 79 additions and 64 deletions
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57
src/backend/executor/nodeSubplan.c
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@@ -481,8 +481,8 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
Assert(subplan->subLinkType == ANY_SUBLINK);
/*
* If we already had any hash tables, destroy 'em; then create empty hash
* table(s).
* If we already had any hash tables, reset 'em; otherwise create empty
* hash table(s).
*
* If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
* NULL) results of the IN operation, then we have to store subplan output
@@ -505,17 +505,21 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
if (nbuckets < 1)
nbuckets = 1;
node->hashtable = BuildTupleHashTable(node->parent,
node->descRight,
ncols,
node->keyColIdx,
node->tab_eq_funcoids,
node->tab_hash_funcs,
nbuckets,
0,
node->hashtablecxt,
node->hashtempcxt,
false);
if (node->hashtable)
ResetTupleHashTable(node->hashtable);
else
node->hashtable = BuildTupleHashTableExt(node->parent,
node->descRight,
ncols,
node->keyColIdx,
node->tab_eq_funcoids,
node->tab_hash_funcs,
nbuckets,
0,
node->planstate->state->es_query_cxt,
node->hashtablecxt,
node->hashtempcxt,
false);
if (!subplan->unknownEqFalse)
{
@@ -527,17 +531,22 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
if (nbuckets < 1)
nbuckets = 1;
}
node->hashnulls = BuildTupleHashTable(node->parent,
node->descRight,
ncols,
node->keyColIdx,
node->tab_eq_funcoids,
node->tab_hash_funcs,
nbuckets,
0,
node->hashtablecxt,
node->hashtempcxt,
false);
if (node->hashnulls)
ResetTupleHashTable(node->hashtable);
else
node->hashnulls = BuildTupleHashTableExt(node->parent,
node->descRight,
ncols,
node->keyColIdx,
node->tab_eq_funcoids,
node->tab_hash_funcs,
nbuckets,
0,
node->planstate->state->es_query_cxt,
node->hashtablecxt,
node->hashtempcxt,
false);
}
/*