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Improve INTERSECT/EXCEPT hashing by realizing that we don't need to make any

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hashtable entries for tuples that are found only in the second input: they
can never contribute to the output.  Furthermore, this implies that the
planner should endeavor to put first the smaller (in number of groups) input
relation for an INTERSECT.  Implement that, and upgrade prepunion's estimation
of the number of rows returned by setops so that there's some amount of sanity
in the estimate of which one is smaller.
This commit is contained in:
Tom Lane
2008-08-07 19:35:02 +00:00
parent 368df30427
commit af95d7aa63
9 changed files with 278 additions and 159 deletions
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104
src/backend/optimizer/util/tlist.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.80 2008/08/07 01:11:50 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.81 2008/08/07 19:35:02 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -133,6 +133,69 @@ add_to_flat_tlist(List *tlist, List *vars)
}
/*
* get_tlist_exprs
* Get just the expression subtrees of a tlist
*
* Resjunk columns are ignored unless includeJunk is true
*/
List *
get_tlist_exprs(List *tlist, bool includeJunk)
{
List *result = NIL;
ListCell *l;
foreach(l, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
if (tle->resjunk && !includeJunk)
continue;
result = lappend(result, tle->expr);
}
return result;
}
/*
* Does tlist have same output datatypes as listed in colTypes?
*
* Resjunk columns are ignored if junkOK is true; otherwise presence of
* a resjunk column will always cause a 'false' result.
*
* Note: currently no callers care about comparing typmods.
*/
bool
tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK)
{
ListCell *l;
ListCell *curColType = list_head(colTypes);
foreach(l, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
if (tle->resjunk)
{
if (!junkOK)
return false;
}
else
{
if (curColType == NULL)
return false; /* tlist longer than colTypes */
if (exprType((Node *) tle->expr) != lfirst_oid(curColType))
return false;
curColType = lnext(curColType);
}
}
if (curColType != NULL)
return false; /* tlist shorter than colTypes */
return true;
}
/*
* get_sortgroupref_tle
* Find the targetlist entry matching the given SortGroupRef index,
@@ -303,42 +366,3 @@ grouping_is_hashable(List *groupClause)
}
return true;
}
/*
* Does tlist have same output datatypes as listed in colTypes?
*
* Resjunk columns are ignored if junkOK is true; otherwise presence of
* a resjunk column will always cause a 'false' result.
*
* Note: currently no callers care about comparing typmods.
*/
bool
tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK)
{
ListCell *l;
ListCell *curColType = list_head(colTypes);
foreach(l, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
if (tle->resjunk)
{
if (!junkOK)
return false;
}
else
{
if (curColType == NULL)
return false; /* tlist longer than colTypes */
if (exprType((Node *) tle->expr) != lfirst_oid(curColType))
return false;
curColType = lnext(curColType);
}
}
if (curColType != NULL)
return false; /* tlist shorter than colTypes */
return true;
}