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This clause changes the behavior of SELECT locking clauses in the presence of locked rows: instead of causing a process to block waiting for the locks held by other processes (or raise an error, with NOWAIT), SKIP LOCKED makes the new reader skip over such rows. While this is not appropriate behavior for general purposes, there are some cases in which it is useful, such as queue-like tables. Catalog version bumped because this patch changes the representation of stored rules. Reviewed by Craig Ringer (based on a previous attempt at an implementation by Simon Riggs, who also provided input on the syntax used in the current patch), David Rowley, and Álvaro Herrera. Author: Thomas Munro
185 lines
6.8 KiB
C
185 lines
6.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* heapam.h
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* POSTGRES heap access method definitions.
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*
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*
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* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/access/heapam.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef HEAPAM_H
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#define HEAPAM_H
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#include "access/sdir.h"
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#include "access/skey.h"
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#include "nodes/primnodes.h"
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#include "storage/bufpage.h"
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#include "storage/lock.h"
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#include "utils/lockwaitpolicy.h"
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#include "utils/relcache.h"
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#include "utils/snapshot.h"
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/* "options" flag bits for heap_insert */
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#define HEAP_INSERT_SKIP_WAL 0x0001
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#define HEAP_INSERT_SKIP_FSM 0x0002
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#define HEAP_INSERT_FROZEN 0x0004
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typedef struct BulkInsertStateData *BulkInsertState;
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/*
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* Possible lock modes for a tuple.
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*/
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typedef enum LockTupleMode
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{
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/* SELECT FOR KEY SHARE */
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LockTupleKeyShare,
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/* SELECT FOR SHARE */
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LockTupleShare,
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/* SELECT FOR NO KEY UPDATE, and UPDATEs that don't modify key columns */
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LockTupleNoKeyExclusive,
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/* SELECT FOR UPDATE, UPDATEs that modify key columns, and DELETE */
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LockTupleExclusive
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} LockTupleMode;
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#define MaxLockTupleMode LockTupleExclusive
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/*
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* When heap_update, heap_delete, or heap_lock_tuple fail because the target
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* tuple is already outdated, they fill in this struct to provide information
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* to the caller about what happened.
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* ctid is the target's ctid link: it is the same as the target's TID if the
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* target was deleted, or the location of the replacement tuple if the target
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* was updated.
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* xmax is the outdating transaction's XID. If the caller wants to visit the
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* replacement tuple, it must check that this matches before believing the
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* replacement is really a match.
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* cmax is the outdating command's CID, but only when the failure code is
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* HeapTupleSelfUpdated (i.e., something in the current transaction outdated
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* the tuple); otherwise cmax is zero. (We make this restriction because
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* HeapTupleHeaderGetCmax doesn't work for tuples outdated in other
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* transactions.)
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*/
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typedef struct HeapUpdateFailureData
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{
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ItemPointerData ctid;
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TransactionId xmax;
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CommandId cmax;
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} HeapUpdateFailureData;
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/* ----------------
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* function prototypes for heap access method
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*
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* heap_create, heap_create_with_catalog, and heap_drop_with_catalog
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* are declared in catalog/heap.h
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* ----------------
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*/
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/* in heap/heapam.c */
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extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
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extern Relation try_relation_open(Oid relationId, LOCKMODE lockmode);
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extern Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
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extern Relation relation_openrv_extended(const RangeVar *relation,
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LOCKMODE lockmode, bool missing_ok);
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extern void relation_close(Relation relation, LOCKMODE lockmode);
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extern Relation heap_open(Oid relationId, LOCKMODE lockmode);
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extern Relation heap_openrv(const RangeVar *relation, LOCKMODE lockmode);
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extern Relation heap_openrv_extended(const RangeVar *relation,
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LOCKMODE lockmode, bool missing_ok);
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#define heap_close(r,l) relation_close(r,l)
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/* struct definition appears in relscan.h */
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typedef struct HeapScanDescData *HeapScanDesc;
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/*
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* HeapScanIsValid
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* True iff the heap scan is valid.
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*/
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#define HeapScanIsValid(scan) PointerIsValid(scan)
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extern HeapScanDesc heap_beginscan(Relation relation, Snapshot snapshot,
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int nkeys, ScanKey key);
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extern HeapScanDesc heap_beginscan_catalog(Relation relation, int nkeys,
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ScanKey key);
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extern HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot,
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int nkeys, ScanKey key,
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bool allow_strat, bool allow_sync);
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extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
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int nkeys, ScanKey key);
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extern void heap_rescan(HeapScanDesc scan, ScanKey key);
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extern void heap_endscan(HeapScanDesc scan);
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extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
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extern bool heap_fetch(Relation relation, Snapshot snapshot,
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HeapTuple tuple, Buffer *userbuf, bool keep_buf,
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Relation stats_relation);
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extern bool heap_hot_search_buffer(ItemPointer tid, Relation relation,
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Buffer buffer, Snapshot snapshot, HeapTuple heapTuple,
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bool *all_dead, bool first_call);
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extern bool heap_hot_search(ItemPointer tid, Relation relation,
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Snapshot snapshot, bool *all_dead);
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extern void heap_get_latest_tid(Relation relation, Snapshot snapshot,
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ItemPointer tid);
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extern void setLastTid(const ItemPointer tid);
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extern BulkInsertState GetBulkInsertState(void);
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extern void FreeBulkInsertState(BulkInsertState);
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extern Oid heap_insert(Relation relation, HeapTuple tup, CommandId cid,
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int options, BulkInsertState bistate);
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extern void heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
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CommandId cid, int options, BulkInsertState bistate);
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extern HTSU_Result heap_delete(Relation relation, ItemPointer tid,
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CommandId cid, Snapshot crosscheck, bool wait,
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HeapUpdateFailureData *hufd);
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extern HTSU_Result heap_update(Relation relation, ItemPointer otid,
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HeapTuple newtup,
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CommandId cid, Snapshot crosscheck, bool wait,
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HeapUpdateFailureData *hufd, LockTupleMode *lockmode);
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extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
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CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
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bool follow_update,
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Buffer *buffer, HeapUpdateFailureData *hufd);
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extern void heap_inplace_update(Relation relation, HeapTuple tuple);
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extern bool heap_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
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TransactionId cutoff_multi);
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extern bool heap_tuple_needs_freeze(HeapTupleHeader tuple, TransactionId cutoff_xid,
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MultiXactId cutoff_multi, Buffer buf);
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extern Oid simple_heap_insert(Relation relation, HeapTuple tup);
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extern void simple_heap_delete(Relation relation, ItemPointer tid);
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extern void simple_heap_update(Relation relation, ItemPointer otid,
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HeapTuple tup);
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extern void heap_markpos(HeapScanDesc scan);
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extern void heap_restrpos(HeapScanDesc scan);
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extern void heap_sync(Relation relation);
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/* in heap/pruneheap.c */
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extern void heap_page_prune_opt(Relation relation, Buffer buffer);
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extern int heap_page_prune(Relation relation, Buffer buffer,
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TransactionId OldestXmin,
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bool report_stats, TransactionId *latestRemovedXid);
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extern void heap_page_prune_execute(Buffer buffer,
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OffsetNumber *redirected, int nredirected,
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OffsetNumber *nowdead, int ndead,
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OffsetNumber *nowunused, int nunused);
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extern void heap_get_root_tuples(Page page, OffsetNumber *root_offsets);
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/* in heap/syncscan.c */
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extern void ss_report_location(Relation rel, BlockNumber location);
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extern BlockNumber ss_get_location(Relation rel, BlockNumber relnblocks);
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extern void SyncScanShmemInit(void);
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extern Size SyncScanShmemSize(void);
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#endif /* HEAPAM_H */
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