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/*-------------------------------------------------------------------------
*
* skey.h
* POSTGRES scan key definitions.
*
*
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/skey.h,v 1.32 2006/03/05 15:58:53 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef SKEY_H
#define SKEY_H
#include "access/attnum.h"
#include "fmgr.h"
/*
* Strategy numbers identify the semantics that particular operators have
* with respect to particular operator classes. In some cases a strategy
* subtype (an OID) is used as further information.
*/
typedef uint16 StrategyNumber;
#define InvalidStrategy ((StrategyNumber) 0)
/*
* We define the strategy numbers for B-tree indexes here, to avoid having
* to import access/nbtree.h into a lot of places that shouldn't need it.
*/
#define BTLessStrategyNumber 1
#define BTLessEqualStrategyNumber 2
#define BTEqualStrategyNumber 3
#define BTGreaterEqualStrategyNumber 4
#define BTGreaterStrategyNumber 5
#define BTMaxStrategyNumber 5
/*
* A ScanKey represents the application of a comparison operator between
* a table or index column and a constant. When it's part of an array of
* ScanKeys, the comparison conditions are implicitly ANDed. The index
* column is the left argument of the operator, if it's a binary operator.
* (The data structure can support unary indexable operators too; in that
* case sk_argument would go unused. This is not currently implemented.)
*
* For an index scan, sk_strategy and sk_subtype must be set correctly for
* the operator. When using a ScanKey in a heap scan, these fields are not
* used and may be set to InvalidStrategy/InvalidOid.
*
* Note: in some places, ScanKeys are used as a convenient representation
* for the invocation of an access method support procedure. In this case
* sk_strategy/sk_subtype are not meaningful, and sk_func may refer to a
* function that returns something other than boolean.
*/
typedef struct ScanKeyData
{
int sk_flags; /* flags, see below */
AttrNumber sk_attno; /* table or index column number */
StrategyNumber sk_strategy; /* operator strategy number */
Oid sk_subtype; /* strategy subtype */
FmgrInfo sk_func; /* lookup info for function to call */
Datum sk_argument; /* data to compare */
} ScanKeyData;
typedef ScanKeyData *ScanKey;
/*
* About row comparisons:
*
* The ScanKey data structure also supports row comparisons, that is ordered
* tuple comparisons like (x, y) > (c1, c2), having the SQL-spec semantics
* "x > c1 OR (x = c1 AND y > c2)". Note that this is currently only
* implemented for btree index searches, not for heapscans or any other index
* type. A row comparison is represented by a "header" ScanKey entry plus
* a separate array of ScanKeys, one for each column of the row comparison.
* The header entry has these properties:
* sk_flags = SK_ROW_HEADER
* sk_attno = index column number for leading column of row comparison
* sk_strategy = btree strategy code for semantics of row comparison
* (ie, < <= > or >=)
* sk_subtype, sk_func: not used
* sk_argument: pointer to subsidiary ScanKey array
* If the header is part of a ScanKey array that's sorted by attno, it
* must be sorted according to the leading column number.
*
* The subsidiary ScanKey array appears in logical column order of the row
* comparison, which may be different from index column order. The array
* elements are like a normal ScanKey array except that:
* sk_flags must include SK_ROW_MEMBER, plus SK_ROW_END in the last
* element (needed since row header does not include a count)
* sk_func points to the btree comparison support function for the
* opclass, NOT the operator's implementation function.
* sk_strategy must be the same in all elements of the subsidiary array,
* that is, the same as in the header entry.
*/
/*
* ScanKeyData sk_flags
*
* sk_flags bits 0-15 are reserved for system-wide use (symbols for those
* bits should be defined here). Bits 16-31 are reserved for use within
* individual index access methods.
*/
#define SK_ISNULL 0x0001 /* sk_argument is NULL */
#define SK_UNARY 0x0002 /* unary operator (currently unsupported) */
#define SK_ROW_HEADER 0x0004 /* row comparison header (see above) */
#define SK_ROW_MEMBER 0x0008 /* row comparison member (see above) */
#define SK_ROW_END 0x0010 /* last row comparison member (see above) */
/*
* prototypes for functions in access/common/scankey.c
*/
extern void ScanKeyInit(ScanKey entry,
AttrNumber attributeNumber,
StrategyNumber strategy,
RegProcedure procedure,
Datum argument);
extern void ScanKeyEntryInitialize(ScanKey entry,
int flags,
AttrNumber attributeNumber,
StrategyNumber strategy,
Oid subtype,
RegProcedure procedure,
Datum argument);
extern void ScanKeyEntryInitializeWithInfo(ScanKey entry,
int flags,
AttrNumber attributeNumber,
StrategyNumber strategy,
Oid subtype,
FmgrInfo *finfo,
Datum argument);
#endif /* SKEY_H */
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