granicus.if.org Git - postgresql/blob - src/backend/access/gist/gistscan.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * gistscan.c
   4  *        routines to manage scans on GiST index relations
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/access/gist/gistscan.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #include "postgres.h"
  16
  17 #include "access/genam.h"
  18 #include "access/gist_private.h"
  19 #include "access/gistscan.h"
  20 #include "access/relscan.h"
  21 #include "storage/bufmgr.h"
  22 #include "utils/memutils.h"
  23
  24 static void gistfreestack(GISTSearchStack *s);
  25
  26 Datum
  27 gistbeginscan(PG_FUNCTION_ARGS)
  28 {
  29         Relation        r = (Relation) PG_GETARG_POINTER(0);
  30         int                     nkeys = PG_GETARG_INT32(1);
  31         int                     norderbys = PG_GETARG_INT32(2);
  32         IndexScanDesc scan;
  33         GISTScanOpaque so;
  34
  35         /* no order by operators allowed */
  36         Assert(norderbys == 0);
  37
  38         scan = RelationGetIndexScan(r, nkeys, norderbys);
  39
  40         /* initialize opaque data */
  41         so = (GISTScanOpaque) palloc(sizeof(GISTScanOpaqueData));
  42         so->stack = NULL;
  43         so->tempCxt = createTempGistContext();
  44         so->curbuf = InvalidBuffer;
  45         so->giststate = (GISTSTATE *) palloc(sizeof(GISTSTATE));
  46         initGISTstate(so->giststate, scan->indexRelation);
  47
  48         scan->opaque = so;
  49
  50         PG_RETURN_POINTER(scan);
  51 }
  52
  53 Datum
  54 gistrescan(PG_FUNCTION_ARGS)
  55 {
  56         IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
  57         ScanKey         key = (ScanKey) PG_GETARG_POINTER(1);
  58         /* remaining arguments are ignored */
  59         GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
  60         int                     i;
  61
  62         /* rescan an existing indexscan --- reset state */
  63         gistfreestack(so->stack);
  64         so->stack = NULL;
  65         /* drop pins on buffers -- no locks held */
  66         if (BufferIsValid(so->curbuf))
  67         {
  68                 ReleaseBuffer(so->curbuf);
  69                 so->curbuf = InvalidBuffer;
  70         }
  71
  72         /*
  73          * Clear all the pointers.
  74          */
  75         ItemPointerSetInvalid(&so->curpos);
  76         so->nPageData = so->curPageData = 0;
  77
  78         so->qual_ok = true;
  79
  80         /* Update scan key, if a new one is given */
  81         if (key && scan->numberOfKeys > 0)
  82         {
  83                 memmove(scan->keyData, key,
  84                                 scan->numberOfKeys * sizeof(ScanKeyData));
  85
  86                 /*
  87                  * Modify the scan key so that all the Consistent method is called for
  88                  * all comparisons. The original operator is passed to the Consistent
  89                  * function in the form of its strategy number, which is available
  90                  * from the sk_strategy field, and its subtype from the sk_subtype
  91                  * field.
  92                  *
  93                  * Next, if any of keys is a NULL and that key is not marked with
  94                  * SK_SEARCHNULL/SK_SEARCHNOTNULL then nothing can be found (ie, we
  95                  * assume all indexable operators are strict).
  96                  */
  97                 for (i = 0; i < scan->numberOfKeys; i++)
  98                 {
  99                         ScanKey         skey = &(scan->keyData[i]);
 100
 101                         skey->sk_func = so->giststate->consistentFn[skey->sk_attno - 1];
 102
 103                         if (skey->sk_flags & SK_ISNULL)
 104                         {
 105                                 if (!(skey->sk_flags & (SK_SEARCHNULL | SK_SEARCHNOTNULL)))
 106                                         so->qual_ok = false;
 107                         }
 108                 }
 109         }
 110
 111         PG_RETURN_VOID();
 112 }
 113
 114 Datum
 115 gistmarkpos(PG_FUNCTION_ARGS)
 116 {
 117         elog(ERROR, "GiST does not support mark/restore");
 118         PG_RETURN_VOID();
 119 }
 120
 121 Datum
 122 gistrestrpos(PG_FUNCTION_ARGS)
 123 {
 124         elog(ERROR, "GiST does not support mark/restore");
 125         PG_RETURN_VOID();
 126 }
 127
 128 Datum
 129 gistendscan(PG_FUNCTION_ARGS)
 130 {
 131         IndexScanDesc scan = (IndexScanDesc) PG_GETARG_POINTER(0);
 132         GISTScanOpaque so = (GISTScanOpaque) scan->opaque;
 133
 134         gistfreestack(so->stack);
 135         if (so->giststate != NULL)
 136                 freeGISTstate(so->giststate);
 137         /* drop pins on buffers -- we aren't holding any locks */
 138         if (BufferIsValid(so->curbuf))
 139                 ReleaseBuffer(so->curbuf);
 140         MemoryContextDelete(so->tempCxt);
 141         pfree(so);
 142
 143         PG_RETURN_VOID();
 144 }
 145
 146 static void
 147 gistfreestack(GISTSearchStack *s)
 148 {
 149         while (s != NULL)
 150         {
 151                 GISTSearchStack *p = s->next;
 152
 153                 pfree(s);
 154                 s = p;
 155         }
 156 }