mirror of https://github.com/postgres/postgres
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
61 lines
1.6 KiB
61 lines
1.6 KiB
/*-------------------------------------------------------------------------
|
|
*
|
|
* skipsupport.c
|
|
* Support routines for B-Tree skip scan.
|
|
*
|
|
*
|
|
* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
*
|
|
* IDENTIFICATION
|
|
* src/backend/utils/adt/skipsupport.c
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
|
|
#include "postgres.h"
|
|
|
|
#include "access/nbtree.h"
|
|
#include "utils/lsyscache.h"
|
|
#include "utils/skipsupport.h"
|
|
|
|
/*
|
|
* Fill in SkipSupport given an operator class (opfamily + opcintype).
|
|
*
|
|
* On success, returns skip support struct, allocating in caller's memory
|
|
* context. Otherwise returns NULL, indicating that operator class has no
|
|
* skip support function.
|
|
*/
|
|
SkipSupport
|
|
PrepareSkipSupportFromOpclass(Oid opfamily, Oid opcintype, bool reverse)
|
|
{
|
|
Oid skipSupportFunction;
|
|
SkipSupport sksup;
|
|
|
|
/* Look for a skip support function */
|
|
skipSupportFunction = get_opfamily_proc(opfamily, opcintype, opcintype,
|
|
BTSKIPSUPPORT_PROC);
|
|
if (!OidIsValid(skipSupportFunction))
|
|
return NULL;
|
|
|
|
sksup = palloc(sizeof(SkipSupportData));
|
|
OidFunctionCall1(skipSupportFunction, PointerGetDatum(sksup));
|
|
|
|
if (reverse)
|
|
{
|
|
/*
|
|
* DESC/reverse case: swap low_elem with high_elem, and swap decrement
|
|
* with increment
|
|
*/
|
|
Datum low_elem = sksup->low_elem;
|
|
SkipSupportIncDec decrement = sksup->decrement;
|
|
|
|
sksup->low_elem = sksup->high_elem;
|
|
sksup->decrement = sksup->increment;
|
|
|
|
sksup->high_elem = low_elem;
|
|
sksup->increment = decrement;
|
|
}
|
|
|
|
return sksup;
|
|
}
|
|
|