/* -------------------------------------------------------------------------
 *
 * skey.h
 *	  openGauss scan key definitions.
 *
 *
 * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/skey.h
 *
 * -------------------------------------------------------------------------
 */
#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

#ifndef MADLIB
static_assert(BTMaxStrategyNumber == 5, "Strategy Number is not matched");
#endif

/*
 * 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.
 *
 * If the operator is collation-sensitive, sk_collation must be set
 * correctly as well.
 *
 * A ScanKey can also represent a ScalarArrayOpExpr, that is a condition
 * "column op ANY(ARRAY[...])".  This is signaled by the SK_SEARCHARRAY
 * flag bit.  The sk_argument is not a value of the operator's right-hand
 * argument type, but rather an array of such values, and the per-element
 * comparisons are to be ORed together.
 *
 * A ScanKey can also represent a condition "column IS NULL" or "column
 * IS NOT NULL"; these cases are signaled by the SK_SEARCHNULL and
 * SK_SEARCHNOTNULL flag bits respectively.  The argument is always NULL,
 * and the sk_strategy, sk_subtype, sk_collation, and sk_func fields are
 * not used (unless set by the index AM).
 *
 * SK_SEARCHARRAY, SK_SEARCHNULL and SK_SEARCHNOTNULL are supported only
 * for index scans, not heap scans; and not all index AMs support them,
 * only those that set amsearcharray or amsearchnulls respectively.
 *
 * A ScanKey can also represent an ordering operator invocation, that is
 * an ordering requirement "ORDER BY indexedcol op constant".  This looks
 * the same as a comparison operator, except that the operator doesn't
 * (usually) yield boolean.  We mark such ScanKeys with SK_ORDER_BY.
 * SK_SEARCHARRAY, SK_SEARCHNULL, SK_SEARCHNOTNULL cannot be used here.
 *
 * 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 (but sk_collation can be); and
 * sk_func may refer to a function that returns something other than boolean.
 */
typedef struct ScanKeyData {
    uint32 sk_flags;            /* flags, see below */
    AttrNumber sk_attno;        /* table or index column number */
    StrategyNumber sk_strategy; /* operator strategy number */
    Oid sk_subtype;             /* strategy subtype */
    Oid sk_collation;           /* collation to use, if needed */
    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_collation, 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.
 * SK_SEARCHARRAY, SK_SEARCHNULL, SK_SEARCHNOTNULL cannot be used here.
 */

/*
 * 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 (not supported!) */
#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 */
#define SK_SEARCHARRAY 0x0020 /* scankey represents ScalarArrayOp */
#define SK_SEARCHNULL 0x0040  /* scankey represents "col IS NULL" */
#define SK_SEARCHNOTNULL                                     \
    0x0080                 /* scankey represents "col IS NOT \
                            * NULL" */
#define SK_ORDER_BY 0x0100 /* scankey is for ORDER BY op */

/*
 * prototypes for functions in access/common/scankey.c
 */
extern void ScanKeyInit(
    ScanKey entry, AttrNumber attribute_number, StrategyNumber strategy, RegProcedure procedure, Datum argument);
extern void ScanKeyEntryInitialize(ScanKey entry, uint32 flags, AttrNumber attribute_number, StrategyNumber strategy,
    Oid subtype, Oid collation, RegProcedure procedure, Datum argument);
extern void ScanKeyEntryInitializeWithInfo(ScanKey entry, uint32 flags, AttrNumber attribute_number,
    StrategyNumber strategy, Oid subtype, Oid collation, FmgrInfo* finfo, Datum argument);

#endif /* SKEY_H */