src/include/access/relscan.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * relscan.h
   4  *        POSTGRES relation scan descriptor definitions.
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * src/include/access/relscan.h
  11  *
  12  *-------------------------------------------------------------------------
  13  */
  14 #ifndef RELSCAN_H
  15 #define RELSCAN_H
  16
  17 #include "access/htup_details.h"
  18 #include "access/itup.h"
  19 #include "port/atomics.h"
  20 #include "storage/buf.h"
  21 #include "storage/spin.h"
  22 #include "utils/relcache.h"
  23
  24
  25 struct ParallelTableScanDescData;
  26
  27 /*
  28  * Generic descriptor for table scans. This is the base-class for table scans,
  29  * which needs to be embedded in the scans of individual AMs.
  30  */
  31 typedef struct TableScanDescData
  32 {
  33         /* scan parameters */
  34         Relation        rs_rd;                  /* heap relation descriptor */
  35         struct SnapshotData *rs_snapshot;       /* snapshot to see */
  36         int                     rs_nkeys;               /* number of scan keys */
  37         struct ScanKeyData *rs_key; /* array of scan key descriptors */
  38
  39         /* Range of ItemPointers for table_scan_getnextslot_tidrange() to scan. */
  40         ItemPointerData rs_mintid;
  41         ItemPointerData rs_maxtid;
  42
  43         /*
  44          * Information about type and behaviour of the scan, a bitmask of members
  45          * of the ScanOptions enum (see tableam.h).
  46          */
  47         uint32          rs_flags;
  48
  49         struct ParallelTableScanDescData *rs_parallel;  /* parallel scan
  50                                                                                                          * information */
  51 } TableScanDescData;
  52 typedef struct TableScanDescData *TableScanDesc;
  53
  54 /*
  55  * Shared state for parallel table scan.
  56  *
  57  * Each backend participating in a parallel table scan has its own
  58  * TableScanDesc in backend-private memory, and those objects all contain a
  59  * pointer to this structure.  The information here must be sufficient to
  60  * properly initialize each new TableScanDesc as workers join the scan, and it
  61  * must act as a information what to scan for those workers.
  62  */
  63 typedef struct ParallelTableScanDescData
  64 {
  65         Oid                     phs_relid;              /* OID of relation to scan */
  66         bool            phs_syncscan;   /* report location to syncscan logic? */
  67         bool            phs_snapshot_any;       /* SnapshotAny, not phs_snapshot_data? */
  68         Size            phs_snapshot_off;       /* data for snapshot */
  69 } ParallelTableScanDescData;
  70 typedef struct ParallelTableScanDescData *ParallelTableScanDesc;
  71
  72 /*
  73  * Shared state for parallel table scans, for block oriented storage.
  74  */
  75 typedef struct ParallelBlockTableScanDescData
  76 {
  77         ParallelTableScanDescData base;
  78
  79         BlockNumber phs_nblocks;        /* # blocks in relation at start of scan */
  80         slock_t         phs_mutex;              /* mutual exclusion for setting startblock */
  81         BlockNumber phs_startblock; /* starting block number */
  82         pg_atomic_uint64 phs_nallocated;        /* number of blocks allocated to
  83                                                                                  * workers so far. */
  84 }                       ParallelBlockTableScanDescData;
  85 typedef struct ParallelBlockTableScanDescData *ParallelBlockTableScanDesc;
  86
  87 /*
  88  * Per backend state for parallel table scan, for block-oriented storage.
  89  */
  90 typedef struct ParallelBlockTableScanWorkerData
  91 {
  92         uint64          phsw_nallocated;        /* Current # of blocks into the scan */
  93         uint32          phsw_chunk_remaining;   /* # blocks left in this chunk */
  94         uint32          phsw_chunk_size;        /* The number of blocks to allocate in
  95                                                                          * each I/O chunk for the scan */
  96 } ParallelBlockTableScanWorkerData;
  97 typedef struct ParallelBlockTableScanWorkerData *ParallelBlockTableScanWorker;
  98
  99 /*
 100  * Base class for fetches from a table via an index. This is the base-class
 101  * for such scans, which needs to be embedded in the respective struct for
 102  * individual AMs.
 103  */
 104 typedef struct IndexFetchTableData
 105 {
 106         Relation        rel;
 107 } IndexFetchTableData;
 108
 109 /*
 110  * We use the same IndexScanDescData structure for both amgettuple-based
 111  * and amgetbitmap-based index scans.  Some fields are only relevant in
 112  * amgettuple-based scans.
 113  */
 114 typedef struct IndexScanDescData
 115 {
 116         /* scan parameters */
 117         Relation        heapRelation;   /* heap relation descriptor, or NULL */
 118         Relation        indexRelation;  /* index relation descriptor */
 119         struct SnapshotData *xs_snapshot;       /* snapshot to see */
 120         int                     numberOfKeys;   /* number of index qualifier conditions */
 121         int                     numberOfOrderBys;       /* number of ordering operators */
 122         struct ScanKeyData *keyData;    /* array of index qualifier descriptors */
 123         struct ScanKeyData *orderByData;        /* array of ordering op descriptors */
 124         bool            xs_want_itup;   /* caller requests index tuples */
 125         bool            xs_temp_snap;   /* unregister snapshot at scan end? */
 126
 127         /* signaling to index AM about killing index tuples */
 128         bool            kill_prior_tuple;       /* last-returned tuple is dead */
 129         bool            ignore_killed_tuples;   /* do not return killed entries */
 130         bool            xactStartedInRecovery;  /* prevents killing/seeing killed
 131                                                                                  * tuples */
 132
 133         /* index access method's private state */
 134         void       *opaque;                     /* access-method-specific info */
 135
 136         /*
 137          * In an index-only scan, a successful amgettuple call must fill either
 138          * xs_itup (and xs_itupdesc) or xs_hitup (and xs_hitupdesc) to provide the
 139          * data returned by the scan.  It can fill both, in which case the heap
 140          * format will be used.
 141          */
 142         IndexTuple      xs_itup;                /* index tuple returned by AM */
 143         struct TupleDescData *xs_itupdesc;      /* rowtype descriptor of xs_itup */
 144         HeapTuple       xs_hitup;               /* index data returned by AM, as HeapTuple */
 145         struct TupleDescData *xs_hitupdesc; /* rowtype descriptor of xs_hitup */
 146
 147         ItemPointerData xs_heaptid; /* result */
 148         bool            xs_heap_continue;       /* T if must keep walking, potential
 149                                                                          * further results */
 150         IndexFetchTableData *xs_heapfetch;
 151
 152         bool            xs_recheck;             /* T means scan keys must be rechecked */
 153
 154         /*
 155          * When fetching with an ordering operator, the values of the ORDER BY
 156          * expressions of the last returned tuple, according to the index.  If
 157          * xs_recheckorderby is true, these need to be rechecked just like the
 158          * scan keys, and the values returned here are a lower-bound on the actual
 159          * values.
 160          */
 161         Datum      *xs_orderbyvals;
 162         bool       *xs_orderbynulls;
 163         bool            xs_recheckorderby;
 164
 165         /* parallel index scan information, in shared memory */
 166         struct ParallelIndexScanDescData *parallel_scan;
 167 }                       IndexScanDescData;
 168
 169 /* Generic structure for parallel scans */
 170 typedef struct ParallelIndexScanDescData
 171 {
 172         Oid                     ps_relid;
 173         Oid                     ps_indexid;
 174         Size            ps_offset;              /* Offset in bytes of am specific structure */
 175         char            ps_snapshot_data[FLEXIBLE_ARRAY_MEMBER];
 176 }                       ParallelIndexScanDescData;
 177
 178 struct TupleTableSlot;
 179
 180 /* Struct for storage-or-index scans of system tables */
 181 typedef struct SysScanDescData
 182 {
 183         Relation        heap_rel;               /* catalog being scanned */
 184         Relation        irel;                   /* NULL if doing heap scan */
 185         struct TableScanDescData *scan; /* only valid in storage-scan case */
 186         struct IndexScanDescData *iscan;        /* only valid in index-scan case */
 187         struct SnapshotData *snapshot;  /* snapshot to unregister at end of scan */
 188         struct TupleTableSlot *slot;
 189 }                       SysScanDescData;
 190
 191 #endif                                                  /* RELSCAN_H */