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relscan.h
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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 
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. */
42 
43  /*
44  * Information about type and behaviour of the scan, a bitmask of members
45  * of the ScanOptions enum (see tableam.h).
46  */
48 
49  struct ParallelTableScanDescData *rs_parallel; /* parallel scan
50  * information */
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  */
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 */
71 
72 /*
73  * Shared state for parallel table scans, for block oriented storage.
74  */
76 {
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. */
86 
87 /*
88  * Per backend state for parallel table scan, for block-oriented storage.
89  */
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 */
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 {
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 
148  bool xs_heap_continue; /* T if must keep walking, potential
149  * further results */
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  */
164 
165  /* parallel index scan information, in shared memory */
168 
169 /* Generic structure for parallel scans */
171 {
174  Size ps_offset; /* Offset in bytes of am specific structure */
175  char ps_snapshot_data[FLEXIBLE_ARRAY_MEMBER];
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 */
190 
191 #endif /* RELSCAN_H */
pg_atomic_uint64 phs_nallocated
Definition: relscan.h:82
int slock_t
Definition: s_lock.h:958
Relation irel
Definition: relscan.h:184
ItemPointerData rs_mintid
Definition: relscan.h:40
Relation heap_rel
Definition: relscan.h:183
struct IndexFetchTableData IndexFetchTableData
ParallelTableScanDescData base
Definition: relscan.h:77
struct ScanKeyData * orderByData
Definition: relscan.h:123
IndexTuple xs_itup
Definition: relscan.h:142
struct TableScanDescData TableScanDescData
struct SnapshotData * snapshot
Definition: relscan.h:187
struct ParallelBlockTableScanWorkerData ParallelBlockTableScanWorkerData
struct ParallelBlockTableScanDescData * ParallelBlockTableScanDesc
Definition: relscan.h:85
struct ParallelBlockTableScanDescData ParallelBlockTableScanDescData
struct TupleDescData * xs_itupdesc
Definition: relscan.h:143
struct TupleDescData * xs_hitupdesc
Definition: relscan.h:145
#define FLEXIBLE_ARRAY_MEMBER
Definition: c.h:350
Datum * xs_orderbyvals
Definition: relscan.h:161
bool xs_recheckorderby
Definition: relscan.h:163
struct SnapshotData * xs_snapshot
Definition: relscan.h:119
uint32 BlockNumber
Definition: block.h:31
unsigned int Oid
Definition: postgres_ext.h:31
uint32 rs_flags
Definition: relscan.h:47
struct IndexScanDescData * iscan
Definition: relscan.h:186
struct TupleTableSlot * slot
Definition: relscan.h:188
bool ignore_killed_tuples
Definition: relscan.h:129
Relation indexRelation
Definition: relscan.h:118
Relation heapRelation
Definition: relscan.h:117
bool * xs_orderbynulls
Definition: relscan.h:162
struct TableScanDescData * scan
Definition: relscan.h:185
ItemPointerData xs_heaptid
Definition: relscan.h:147
bool xactStartedInRecovery
Definition: relscan.h:130
unsigned int uint32
Definition: c.h:441
struct ScanKeyData * rs_key
Definition: relscan.h:37
struct IndexScanDescData IndexScanDescData
ItemPointerData rs_maxtid
Definition: relscan.h:41
struct ParallelIndexScanDescData * parallel_scan
Definition: relscan.h:166
uintptr_t Datum
Definition: postgres.h:411
struct SysScanDescData SysScanDescData
IndexFetchTableData * xs_heapfetch
Definition: relscan.h:150
struct ParallelTableScanDescData * ParallelTableScanDesc
Definition: relscan.h:70
size_t Size
Definition: c.h:540
bool xs_heap_continue
Definition: relscan.h:148
Relation rs_rd
Definition: relscan.h:34
struct ScanKeyData * keyData
Definition: relscan.h:122
struct SnapshotData * rs_snapshot
Definition: relscan.h:35
HeapTuple xs_hitup
Definition: relscan.h:144
bool kill_prior_tuple
Definition: relscan.h:128
struct ParallelTableScanDescData * rs_parallel
Definition: relscan.h:49
int numberOfOrderBys
Definition: relscan.h:121
struct ParallelTableScanDescData ParallelTableScanDescData
struct ParallelIndexScanDescData ParallelIndexScanDescData
struct ParallelBlockTableScanWorkerData * ParallelBlockTableScanWorker
Definition: relscan.h:97
struct TableScanDescData * TableScanDesc
Definition: relscan.h:52