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/*------------------------------------------------------------------------- * * skey.h * POSTGRES 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 /* * 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 { 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 */ 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 attributeNumber, StrategyNumber strategy, RegProcedure procedure, Datum argument); extern void ScanKeyEntryInitialize(ScanKey entry, int flags, AttrNumber attributeNumber, StrategyNumber strategy, Oid subtype, Oid collation, RegProcedure procedure, Datum argument); extern void ScanKeyEntryInitializeWithInfo(ScanKey entry, int flags, AttrNumber attributeNumber, StrategyNumber strategy, Oid subtype, Oid collation, FmgrInfo *finfo, Datum argument); #endif /* SKEY_H */