src/include/access/relscan.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * relscan.h
   4  *        POSTGRES relation scan descriptor definitions.
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * $PostgreSQL$
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef RELSCAN_H
  15 #define RELSCAN_H
  16
  17 #include "access/htup.h"
  18 #include "access/skey.h"
  19 #include "storage/bufpage.h"
  20 #include "utils/snapshot.h"
  21
  22
  23 typedef struct HeapScanDescData
  24 {
  25         /* scan parameters */
  26         Relation        rs_rd;                  /* heap relation descriptor */
  27         Snapshot        rs_snapshot;    /* snapshot to see */
  28         int                     rs_nkeys;               /* number of scan keys */
  29         ScanKey         rs_key;                 /* array of scan key descriptors */
  30         bool            rs_bitmapscan;  /* true if this is really a bitmap scan */
  31         bool            rs_pageatatime; /* verify visibility page-at-a-time? */
  32         bool            rs_allow_strat; /* allow or disallow use of access strategy */
  33         bool            rs_allow_sync;  /* allow or disallow use of syncscan */
  34
  35         /* state set up at initscan time */
  36         BlockNumber rs_nblocks;         /* number of blocks to scan */
  37         BlockNumber rs_startblock;      /* block # to start at */
  38         BufferAccessStrategy rs_strategy;       /* access strategy for reads */
  39         bool            rs_syncscan;    /* report location to syncscan logic? */
  40
  41         /* scan current state */
  42         bool            rs_inited;              /* false = scan not init'd yet */
  43         HeapTupleData rs_ctup;          /* current tuple in scan, if any */
  44         BlockNumber rs_cblock;          /* current block # in scan, if any */
  45         Buffer          rs_cbuf;                /* current buffer in scan, if any */
  46         /* NB: if rs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
  47         ItemPointerData rs_mctid;       /* marked scan position, if any */
  48
  49         /* these fields only used in page-at-a-time mode and for bitmap scans */
  50         int                     rs_cindex;              /* current tuple's index in vistuples */
  51         int                     rs_mindex;              /* marked tuple's saved index */
  52         int                     rs_ntuples;             /* number of visible tuples on page */
  53         OffsetNumber rs_vistuples[MaxHeapTuplesPerPage];        /* their offsets */
  54 } HeapScanDescData;
  55
  56 typedef HeapScanDescData *HeapScanDesc;
  57
  58 /*
  59  * We use the same IndexScanDescData structure for both amgettuple-based
  60  * and amgetmulti-based index scans.  Some fields are only relevant in
  61  * amgettuple-based scans.
  62  */
  63 typedef struct IndexScanDescData
  64 {
  65         /* scan parameters */
  66         Relation        heapRelation;   /* heap relation descriptor, or NULL */
  67         Relation        indexRelation;  /* index relation descriptor */
  68         Snapshot        xs_snapshot;    /* snapshot to see */
  69         int                     numberOfKeys;   /* number of scan keys */
  70         ScanKey         keyData;                /* array of scan key descriptors */
  71         bool            is_multiscan;   /* TRUE = using amgetmulti */
  72
  73         /* signaling to index AM about killing index tuples */
  74         bool            kill_prior_tuple;               /* last-returned tuple is dead */
  75         bool            ignore_killed_tuples;   /* do not return killed entries */
  76
  77         /* index access method's private state */
  78         void       *opaque;                     /* access-method-specific info */
  79
  80         /*
  81          * xs_ctup/xs_cbuf are valid after a successful index_getnext. After
  82          * index_getnext_indexitem, xs_ctup.t_self contains the heap tuple TID
  83          * from the index entry, but its other fields are not valid.
  84          */
  85         HeapTupleData xs_ctup;          /* current heap tuple, if any */
  86         Buffer          xs_cbuf;                /* current heap buffer in scan, if any */
  87         /* NB: if xs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
  88         TransactionId xs_prev_xmax; /* previous HOT chain member's XMAX, if any */
  89         OffsetNumber xs_next_hot;       /* next member of HOT chain, if any */
  90         bool            xs_hot_dead;    /* T if all members of HOT chain are dead */
  91 } IndexScanDescData;
  92
  93 typedef IndexScanDescData *IndexScanDesc;
  94
  95
  96 /*
  97  * HeapScanIsValid
  98  *              True iff the heap scan is valid.
  99  */
 100 #define HeapScanIsValid(scan) PointerIsValid(scan)
 101
 102 /*
 103  * IndexScanIsValid
 104  *              True iff the index scan is valid.
 105  */
 106 #define IndexScanIsValid(scan) PointerIsValid(scan)
 107
 108 #endif   /* RELSCAN_H */