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/*-------------------------------------------------------------------------
*
* sortsupport.c
* Support routines for accelerated sorting.
*
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/utils/sort/sortsupport.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/gist.h"
#include "access/nbtree.h"
#include "catalog/pg_am.h"
#include "fmgr.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/sortsupport.h"
/* Info needed to use an old-style comparison function as a sort comparator */
typedef struct
{
FmgrInfo flinfo; /* lookup data for comparison function */
FunctionCallInfoBaseData fcinfo; /* reusable callinfo structure */
} SortShimExtra;
#define SizeForSortShimExtra(nargs) (offsetof(SortShimExtra, fcinfo) + SizeForFunctionCallInfo(nargs))
/*
* Shim function for calling an old-style comparator
*
* This is essentially an inlined version of FunctionCall2Coll(), except
* we assume that the FunctionCallInfoBaseData was already mostly set up by
* PrepareSortSupportComparisonShim.
*/
static int
comparison_shim(Datum x, Datum y, SortSupport ssup)
{
SortShimExtra *extra = (SortShimExtra *) ssup->ssup_extra;
Datum result;
extra->fcinfo.args[0].value = x;
extra->fcinfo.args[1].value = y;
/* just for paranoia's sake, we reset isnull each time */
extra->fcinfo.isnull = false;
result = FunctionCallInvoke(&extra->fcinfo);
/* Check for null result, since caller is clearly not expecting one */
if (extra->fcinfo.isnull)
elog(ERROR, "function %u returned NULL", extra->flinfo.fn_oid);
return result;
}
/*
* Set up a shim function to allow use of an old-style btree comparison
* function as if it were a sort support comparator.
*/
void
PrepareSortSupportComparisonShim(Oid cmpFunc, SortSupport ssup)
{
SortShimExtra *extra;
extra = (SortShimExtra *) MemoryContextAlloc(ssup->ssup_cxt,
SizeForSortShimExtra(2));
/* Lookup the comparison function */
fmgr_info_cxt(cmpFunc, &extra->flinfo, ssup->ssup_cxt);
/* We can initialize the callinfo just once and re-use it */
InitFunctionCallInfoData(extra->fcinfo, &extra->flinfo, 2,
ssup->ssup_collation, NULL, NULL);
extra->fcinfo.args[0].isnull = false;
extra->fcinfo.args[1].isnull = false;
ssup->ssup_extra = extra;
ssup->comparator = comparison_shim;
}
/*
* Look up and call sortsupport function to setup SortSupport comparator;
* or if no such function exists or it declines to set up the appropriate
* state, prepare a suitable shim.
*/
static void
FinishSortSupportFunction(Oid opfamily, Oid opcintype, SortSupport ssup)
{
Oid sortSupportFunction;
/* Look for a sort support function */
sortSupportFunction = get_opfamily_proc(opfamily, opcintype, opcintype,
BTSORTSUPPORT_PROC);
if (OidIsValid(sortSupportFunction))
{
/*
* 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));
}
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);
}
}
/*
* Fill in SortSupport given an ordering operator (btree "<" or ">" operator).
*
* Caller must previously have zeroed the SortSupportData structure and then
* filled in ssup_cxt, ssup_collation, and ssup_nulls_first. This will fill
* in ssup_reverse as well as the comparator function pointer.
*/
void
PrepareSortSupportFromOrderingOp(Oid orderingOp, SortSupport ssup)
{
Oid opfamily;
Oid opcintype;
int16 strategy;
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);
FinishSortSupportFunction(opfamily, opcintype, ssup);
}
/*
* Fill in SortSupport given an index relation, attribute, and strategy.
*
* Caller must previously have zeroed the SortSupportData structure and then
* filled in ssup_cxt, ssup_attno, ssup_collation, and ssup_nulls_first. This
* will fill in ssup_reverse (based on the supplied strategy), as well as the
* comparator function pointer.
*/
void
PrepareSortSupportFromIndexRel(Relation indexRel, int16 strategy,
SortSupport ssup)
{
Oid opfamily = indexRel->rd_opfamily[ssup->ssup_attno - 1];
Oid opcintype = indexRel->rd_opcintype[ssup->ssup_attno - 1];
Assert(ssup->comparator == NULL);
if (indexRel->rd_rel->relam != BTREE_AM_OID)
elog(ERROR, "unexpected non-btree AM: %u", indexRel->rd_rel->relam);
if (strategy != BTGreaterStrategyNumber &&
strategy != BTLessStrategyNumber)
elog(ERROR, "unexpected sort support strategy: %d", strategy);
ssup->ssup_reverse = (strategy == BTGreaterStrategyNumber);
FinishSortSupportFunction(opfamily, opcintype, ssup);
}
/*
* Fill in SortSupport given a GiST index relation
*
* Caller must previously have zeroed the SortSupportData structure and then
* filled in ssup_cxt, ssup_attno, ssup_collation, and ssup_nulls_first. This
* will fill in ssup_reverse (always false for GiST index build), as well as
* the comparator function pointer.
*/
void
PrepareSortSupportFromGistIndexRel(Relation indexRel, SortSupport ssup)
{
Oid opfamily = indexRel->rd_opfamily[ssup->ssup_attno - 1];
Oid opcintype = indexRel->rd_opcintype[ssup->ssup_attno - 1];
Oid sortSupportFunction;
Assert(ssup->comparator == NULL);
if (indexRel->rd_rel->relam != GIST_AM_OID)
elog(ERROR, "unexpected non-gist AM: %u", indexRel->rd_rel->relam);
ssup->ssup_reverse = false;
/*
* Look up the sort support function. This is simpler than for B-tree
* indexes because we don't support the old-style btree comparators.
*/
sortSupportFunction = get_opfamily_proc(opfamily, opcintype, opcintype,
GIST_SORTSUPPORT_PROC);
if (!OidIsValid(sortSupportFunction))
elog(ERROR, "missing support function %d(%u,%u) in opfamily %u",
GIST_SORTSUPPORT_PROC, opcintype, opcintype, opfamily);
OidFunctionCall1(sortSupportFunction, PointerGetDatum(ssup));
}
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