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Diffstat (limited to 'src/include/access/skey.h')
| -rw-r--r-- | src/include/access/skey.h | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/src/include/access/skey.h b/src/include/access/skey.h new file mode 100644 index 0000000..7d2df1b --- /dev/null +++ b/src/include/access/skey.h @@ -0,0 +1,151 @@ +/*------------------------------------------------------------------------- + * + * skey.h + * POSTGRES scan key definitions. + * + * + * Portions Copyright (c) 1996-2020, 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 "access/stratnum.h" +#include "fmgr.h" + + +/* + * 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 */ |