1 /*-------------------------------------------------------------------------
4 * POSTGRES relation scan descriptor definitions.
7 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
10 * src/include/access/relscan.h
12 *-------------------------------------------------------------------------
17 #include "access/genam.h"
18 #include "access/heapam.h"
19 #include "access/htup_details.h"
20 #include "access/itup.h"
21 #include "access/tupdesc.h"
24 * Shared state for parallel heap scan.
26 * Each backend participating in a parallel heap scan has its own
27 * HeapScanDesc in backend-private memory, and those objects all contain
28 * a pointer to this structure. The information here must be sufficient
29 * to properly initialize each new HeapScanDesc as workers join the scan,
30 * and it must act as a font of block numbers for those workers.
32 typedef struct ParallelHeapScanDescData
34 Oid phs_relid; /* OID of relation to scan */
35 bool phs_syncscan; /* report location to syncscan logic? */
36 BlockNumber phs_nblocks; /* # blocks in relation at start of scan */
37 slock_t phs_mutex; /* mutual exclusion for block number fields */
38 BlockNumber phs_startblock; /* starting block number */
39 BlockNumber phs_cblock; /* current block number */
40 char phs_snapshot_data[FLEXIBLE_ARRAY_MEMBER];
41 } ParallelHeapScanDescData;
43 typedef struct HeapScanDescData
46 Relation rs_rd; /* heap relation descriptor */
47 Snapshot rs_snapshot; /* snapshot to see */
48 int rs_nkeys; /* number of scan keys */
49 ScanKey rs_key; /* array of scan key descriptors */
50 bool rs_bitmapscan; /* true if this is really a bitmap scan */
51 bool rs_samplescan; /* true if this is really a sample scan */
52 bool rs_pageatatime; /* verify visibility page-at-a-time? */
53 bool rs_allow_strat; /* allow or disallow use of access strategy */
54 bool rs_allow_sync; /* allow or disallow use of syncscan */
55 bool rs_temp_snap; /* unregister snapshot at scan end? */
57 /* state set up at initscan time */
58 BlockNumber rs_nblocks; /* total number of blocks in rel */
59 BlockNumber rs_startblock; /* block # to start at */
60 BlockNumber rs_numblocks; /* max number of blocks to scan */
61 /* rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */
62 BufferAccessStrategy rs_strategy; /* access strategy for reads */
63 bool rs_syncscan; /* report location to syncscan logic? */
65 /* scan current state */
66 bool rs_inited; /* false = scan not init'd yet */
67 HeapTupleData rs_ctup; /* current tuple in scan, if any */
68 BlockNumber rs_cblock; /* current block # in scan, if any */
69 Buffer rs_cbuf; /* current buffer in scan, if any */
70 /* NB: if rs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
71 ParallelHeapScanDesc rs_parallel; /* parallel scan information */
73 /* these fields only used in page-at-a-time mode and for bitmap scans */
74 int rs_cindex; /* current tuple's index in vistuples */
75 int rs_ntuples; /* number of visible tuples on page */
76 OffsetNumber rs_vistuples[MaxHeapTuplesPerPage]; /* their offsets */
80 * We use the same IndexScanDescData structure for both amgettuple-based
81 * and amgetbitmap-based index scans. Some fields are only relevant in
82 * amgettuple-based scans.
84 typedef struct IndexScanDescData
87 Relation heapRelation; /* heap relation descriptor, or NULL */
88 Relation indexRelation; /* index relation descriptor */
89 Snapshot xs_snapshot; /* snapshot to see */
90 int numberOfKeys; /* number of index qualifier conditions */
91 int numberOfOrderBys; /* number of ordering operators */
92 ScanKey keyData; /* array of index qualifier descriptors */
93 ScanKey orderByData; /* array of ordering op descriptors */
94 bool xs_want_itup; /* caller requests index tuples */
96 /* signaling to index AM about killing index tuples */
97 bool kill_prior_tuple; /* last-returned tuple is dead */
98 bool ignore_killed_tuples; /* do not return killed entries */
99 bool xactStartedInRecovery; /* prevents killing/seeing killed
102 /* index access method's private state */
103 void *opaque; /* access-method-specific info */
105 /* in an index-only scan, this is valid after a successful amgettuple */
106 IndexTuple xs_itup; /* index tuple returned by AM */
107 TupleDesc xs_itupdesc; /* rowtype descriptor of xs_itup */
109 /* xs_ctup/xs_cbuf/xs_recheck are valid after a successful index_getnext */
110 HeapTupleData xs_ctup; /* current heap tuple, if any */
111 Buffer xs_cbuf; /* current heap buffer in scan, if any */
112 /* NB: if xs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
113 bool xs_recheck; /* T means scan keys must be rechecked */
116 * When fetching with an ordering operator, the values of the ORDER BY
117 * expressions of the last returned tuple, according to the index. If
118 * xs_recheckorderby is true, these need to be rechecked just like the
119 * scan keys, and the values returned here are a lower-bound on the actual
122 Datum *xs_orderbyvals;
123 bool *xs_orderbynulls;
124 bool xs_recheckorderby;
126 /* state data for traversing HOT chains in index_getnext */
127 bool xs_continue_hot; /* T if must keep walking HOT chain */
130 /* Struct for heap-or-index scans of system tables */
131 typedef struct SysScanDescData
133 Relation heap_rel; /* catalog being scanned */
134 Relation irel; /* NULL if doing heap scan */
135 HeapScanDesc scan; /* only valid in heap-scan case */
136 IndexScanDesc iscan; /* only valid in index-scan case */
137 Snapshot snapshot; /* snapshot to unregister at end of scan */
140 #endif /* RELSCAN_H */