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Don't require sort support functions to provide a comparator.

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This could be useful for datatypes like text, where we might want
to optimize for some collations but not others.  However, this patch
doesn't introduce any new sortsupport functions that work this way;
it merely revises the code so that future patches may do so.

Patch by me.  Review by Peter Geoghegan.
This commit is contained in:
Robert Haas
2014-08-06 16:06:06 -04:00
parent 873de34b71
commit 1d41739e5a
4 changed files with 35 additions and 73 deletions
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42
src/backend/utils/sort/sortsupport.c
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@@ -18,6 +18,7 @@
/* See sortsupport.h */
#define SORTSUPPORT_INCLUDE_DEFINITIONS
#include "access/nbtree.h"
#include "fmgr.h"
#include "utils/lsyscache.h"
#include "utils/sortsupport.h"
@@ -94,24 +95,43 @@ PrepareSortSupportComparisonShim(Oid cmpFunc, SortSupport ssup)
void
PrepareSortSupportFromOrderingOp(Oid orderingOp, SortSupport ssup)
{
Oid sortFunction;
bool issupport;
Oid sortSupportFunction;
Oid opfamily;
Oid opcintype;
int16 strategy;
if (!get_sort_function_for_ordering_op(orderingOp,
&sortFunction,
&issupport,
&ssup->ssup_reverse))
Assert(ssup->comparator == NULL);
/* Find the operator in pg_amop */
if (!get_ordering_op_properties(orderingOp, &opfamily, &opcintype,
&strategy))
elog(ERROR, "operator %u is not a valid ordering operator",
orderingOp);
ssup->ssup_reverse = (strategy == BTGreaterStrategyNumber);
if (issupport)
/* Look for a sort support function */
sortSupportFunction = get_opfamily_proc(opfamily, opcintype, opcintype,
BTSORTSUPPORT_PROC);
if (OidIsValid(sortSupportFunction))
{
/* The sort support function should provide a comparator */
OidFunctionCall1(sortFunction, PointerGetDatum(ssup));
Assert(ssup->comparator != NULL);
/*
* The sort support function can provide a comparator, but it can
* also choose not to so (e.g. based on the selected collation).
*/
OidFunctionCall1(sortSupportFunction, PointerGetDatum(ssup));
}
else
if (ssup->comparator == NULL)
{
Oid sortFunction;
sortFunction = get_opfamily_proc(opfamily, opcintype, opcintype,
BTORDER_PROC);
if (!OidIsValid(sortFunction))
elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
BTORDER_PROC, opcintype, opcintype, opfamily);
/* We'll use a shim to call the old-style btree comparator */
PrepareSortSupportComparisonShim(sortFunction, ssup);
}