PostgreSQL Source Code  git master
relscan.h
Go to the documentation of this file.
1 /*-------------------------------------------------------------------------
2  *
3  * relscan.h
4  * POSTGRES relation scan descriptor definitions.
5  *
6  *
7  * Portions Copyright (c) 1996-2019, 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 
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  /*
40  * Information about type and behaviour of the scan, a bitmask of members
41  * of the ScanOptions enum (see tableam.h).
42  */
44 
45  struct ParallelTableScanDescData *rs_parallel; /* parallel scan
46  * information */
47 
50 
51 /*
52  * Shared state for parallel table scan.
53  *
54  * Each backend participating in a parallel table scan has its own
55  * TableScanDesc in backend-private memory, and those objects all contain a
56  * pointer to this structure. The information here must be sufficient to
57  * properly initialize each new TableScanDesc as workers join the scan, and it
58  * must act as a information what to scan for those workers.
59  */
61 {
62  Oid phs_relid; /* OID of relation to scan */
63  bool phs_syncscan; /* report location to syncscan logic? */
64  bool phs_snapshot_any; /* SnapshotAny, not phs_snapshot_data? */
65  Size phs_snapshot_off; /* data for snapshot */
68 
69 /*
70  * Shared state for parallel table scans, for block oriented storage.
71  */
73 {
75 
76  BlockNumber phs_nblocks; /* # blocks in relation at start of scan */
77  slock_t phs_mutex; /* mutual exclusion for setting startblock */
78  BlockNumber phs_startblock; /* starting block number */
79  pg_atomic_uint64 phs_nallocated; /* number of blocks allocated to
80  * workers so far. */
83 
84 /*
85  * Base class for fetches from a table via an index. This is the base-class
86  * for such scans, which needs to be embedded in the respective struct for
87  * individual AMs.
88  */
89 typedef struct IndexFetchTableData
90 {
93 
94 /*
95  * We use the same IndexScanDescData structure for both amgettuple-based
96  * and amgetbitmap-based index scans. Some fields are only relevant in
97  * amgettuple-based scans.
98  */
99 typedef struct IndexScanDescData
100 {
101  /* scan parameters */
102  Relation heapRelation; /* heap relation descriptor, or NULL */
103  Relation indexRelation; /* index relation descriptor */
104  struct SnapshotData *xs_snapshot; /* snapshot to see */
105  int numberOfKeys; /* number of index qualifier conditions */
106  int numberOfOrderBys; /* number of ordering operators */
107  struct ScanKeyData *keyData; /* array of index qualifier descriptors */
108  struct ScanKeyData *orderByData; /* array of ordering op descriptors */
109  bool xs_want_itup; /* caller requests index tuples */
110  bool xs_temp_snap; /* unregister snapshot at scan end? */
111 
112  /* signaling to index AM about killing index tuples */
113  bool kill_prior_tuple; /* last-returned tuple is dead */
114  bool ignore_killed_tuples; /* do not return killed entries */
115  bool xactStartedInRecovery; /* prevents killing/seeing killed
116  * tuples */
117 
118  /* index access method's private state */
119  void *opaque; /* access-method-specific info */
120 
121  /*
122  * In an index-only scan, a successful amgettuple call must fill either
123  * xs_itup (and xs_itupdesc) or xs_hitup (and xs_hitupdesc) to provide the
124  * data returned by the scan. It can fill both, in which case the heap
125  * format will be used.
126  */
127  IndexTuple xs_itup; /* index tuple returned by AM */
128  struct TupleDescData *xs_itupdesc; /* rowtype descriptor of xs_itup */
129  HeapTuple xs_hitup; /* index data returned by AM, as HeapTuple */
130  struct TupleDescData *xs_hitupdesc; /* rowtype descriptor of xs_hitup */
131 
133  bool xs_heap_continue; /* T if must keep walking, potential
134  * further results */
136 
137  bool xs_recheck; /* T means scan keys must be rechecked */
138 
139  /*
140  * When fetching with an ordering operator, the values of the ORDER BY
141  * expressions of the last returned tuple, according to the index. If
142  * xs_recheckorderby is true, these need to be rechecked just like the
143  * scan keys, and the values returned here are a lower-bound on the actual
144  * values.
145  */
149 
150  /* parallel index scan information, in shared memory */
153 
154 /* Generic structure for parallel scans */
156 {
159  Size ps_offset; /* Offset in bytes of am specific structure */
160  char ps_snapshot_data[FLEXIBLE_ARRAY_MEMBER];
162 
163 struct TupleTableSlot;
164 
165 /* Struct for storage-or-index scans of system tables */
166 typedef struct SysScanDescData
167 {
168  Relation heap_rel; /* catalog being scanned */
169  Relation irel; /* NULL if doing heap scan */
170  struct TableScanDescData *scan; /* only valid in storage-scan case */
171  struct IndexScanDescData *iscan; /* only valid in index-scan case */
172  struct SnapshotData *snapshot; /* snapshot to unregister at end of scan */
175 
176 #endif /* RELSCAN_H */
pg_atomic_uint64 phs_nallocated
Definition: relscan.h:79
int slock_t
Definition: s_lock.h:934
Relation irel
Definition: relscan.h:169
Relation heap_rel
Definition: relscan.h:168
struct IndexFetchTableData IndexFetchTableData
ParallelTableScanDescData base
Definition: relscan.h:74
struct ScanKeyData * orderByData
Definition: relscan.h:108
IndexTuple xs_itup
Definition: relscan.h:127
struct TableScanDescData TableScanDescData
struct SnapshotData * snapshot
Definition: relscan.h:172
struct ParallelBlockTableScanDescData * ParallelBlockTableScanDesc
Definition: relscan.h:82
struct ParallelBlockTableScanDescData ParallelBlockTableScanDescData
struct TupleDescData * xs_itupdesc
Definition: relscan.h:128
struct TupleDescData * xs_hitupdesc
Definition: relscan.h:130
Datum * xs_orderbyvals
Definition: relscan.h:146
bool xs_recheckorderby
Definition: relscan.h:148
struct SnapshotData * xs_snapshot
Definition: relscan.h:104
uint32 BlockNumber
Definition: block.h:31
unsigned int Oid
Definition: postgres_ext.h:31
uint32 rs_flags
Definition: relscan.h:43
struct IndexScanDescData * iscan
Definition: relscan.h:171
struct TupleTableSlot * slot
Definition: relscan.h:173
bool ignore_killed_tuples
Definition: relscan.h:114
Relation indexRelation
Definition: relscan.h:103
Relation heapRelation
Definition: relscan.h:102
bool * xs_orderbynulls
Definition: relscan.h:147
struct TableScanDescData * scan
Definition: relscan.h:170
ItemPointerData xs_heaptid
Definition: relscan.h:132
bool xactStartedInRecovery
Definition: relscan.h:115
unsigned int uint32
Definition: c.h:358
struct ScanKeyData * rs_key
Definition: relscan.h:37
struct IndexScanDescData IndexScanDescData
struct ParallelIndexScanDescData * parallel_scan
Definition: relscan.h:151
uintptr_t Datum
Definition: postgres.h:367
struct SysScanDescData SysScanDescData
IndexFetchTableData * xs_heapfetch
Definition: relscan.h:135
struct ParallelTableScanDescData * ParallelTableScanDesc
Definition: relscan.h:67
size_t Size
Definition: c.h:466
bool xs_heap_continue
Definition: relscan.h:133
Relation rs_rd
Definition: relscan.h:34
struct ScanKeyData * keyData
Definition: relscan.h:107
struct SnapshotData * rs_snapshot
Definition: relscan.h:35
HeapTuple xs_hitup
Definition: relscan.h:129
bool kill_prior_tuple
Definition: relscan.h:113
struct ParallelTableScanDescData * rs_parallel
Definition: relscan.h:45
int numberOfOrderBys
Definition: relscan.h:106
Relation rel
Definition: relscan.h:91
struct ParallelTableScanDescData ParallelTableScanDescData
struct ParallelIndexScanDescData ParallelIndexScanDescData
struct TableScanDescData * TableScanDesc
Definition: relscan.h:49