src/include/nodes/tidbitmap.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * tidbitmap.h
   4  *        PostgreSQL tuple-id (TID) bitmap package
   5  *
   6  * This module provides bitmap data structures that are spiritually
   7  * similar to Bitmapsets, but are specially adapted to store sets of
   8  * tuple identifiers (TIDs), or ItemPointers.  In particular, the division
   9  * of an ItemPointer into BlockNumber and OffsetNumber is catered for.
  10  * Also, since we wish to be able to store very large tuple sets in
  11  * memory with this data structure, we support "lossy" storage, in which
  12  * we no longer remember individual tuple offsets on a page but only the
  13  * fact that a particular page needs to be visited.
  14  *
  15  *
  16  * Copyright (c) 2003-2008, PostgreSQL Global Development Group
  17  *
  18  * $PostgreSQL$
  19  *
  20  *-------------------------------------------------------------------------
  21  */
  22 #ifndef TIDBITMAP_H
  23 #define TIDBITMAP_H
  24
  25 #include "storage/itemptr.h"
  26
  27
  28 /*
  29  * Actual bitmap representation is private to tidbitmap.c.      Callers can
  30  * do IsA(x, TIDBitmap) on it, but nothing else.
  31  */
  32 typedef struct TIDBitmap TIDBitmap;
  33
  34 /* Result structure for tbm_iterate */
  35 typedef struct
  36 {
  37         BlockNumber blockno;            /* page number containing tuples */
  38         int                     ntuples;                /* -1 indicates lossy result */
  39         bool            recheck;                /* should the tuples be rechecked? */
  40         /* Note: recheck is always true if ntuples < 0 */
  41         OffsetNumber offsets[1];        /* VARIABLE LENGTH ARRAY */
  42 } TBMIterateResult;                             /* VARIABLE LENGTH STRUCT */
  43
  44 /* function prototypes in nodes/tidbitmap.c */
  45
  46 extern TIDBitmap *tbm_create(long maxbytes);
  47 extern void tbm_free(TIDBitmap *tbm);
  48
  49 extern void tbm_add_tuples(TIDBitmap *tbm,
  50                                                    const ItemPointer tids, int ntids,
  51                                                    bool recheck);
  52
  53 extern void tbm_union(TIDBitmap *a, const TIDBitmap *b);
  54 extern void tbm_intersect(TIDBitmap *a, const TIDBitmap *b);
  55
  56 extern bool tbm_is_empty(const TIDBitmap *tbm);
  57
  58 extern void tbm_begin_iterate(TIDBitmap *tbm);
  59 extern TBMIterateResult *tbm_iterate(TIDBitmap *tbm);
  60
  61 #endif   /* TIDBITMAP_H */