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postgresql/src/include/access/heapam.h
Simon Riggs d204ef6377 MERGE SQL Command following SQL:2016 
MERGE performs actions that modify rows in the target table
using a source table or query. MERGE provides a single SQL
statement that can conditionally INSERT/UPDATE/DELETE rows
a task that would other require multiple PL statements.
e.g.

MERGE INTO target AS t
USING source AS s
ON t.tid = s.sid
WHEN MATCHED AND t.balance > s.delta THEN
  UPDATE SET balance = t.balance - s.delta
WHEN MATCHED THEN
  DELETE
WHEN NOT MATCHED AND s.delta > 0 THEN
  INSERT VALUES (s.sid, s.delta)
WHEN NOT MATCHED THEN
  DO NOTHING;

MERGE works with regular and partitioned tables, including
column and row security enforcement, as well as support for
row, statement and transition triggers.

MERGE is optimized for OLTP and is parameterizable, though
also useful for large scale ETL/ELT. MERGE is not intended
to be used in preference to existing single SQL commands
for INSERT, UPDATE or DELETE since there is some overhead.
MERGE can be used statically from PL/pgSQL.

MERGE does not yet support inheritance, write rules,
RETURNING clauses, updatable views or foreign tables.
MERGE follows SQL Standard per the most recent SQL:2016.

Includes full tests and documentation, including full
isolation tests to demonstrate the concurrent behavior.

This version written from scratch in 2017 by Simon Riggs,
using docs and tests originally written in 2009. Later work
from Pavan Deolasee has been both complex and deep, leaving
the lead author credit now in his hands.
Extensive discussion of concurrency from Peter Geoghegan,
with thanks for the time and effort contributed.

Various issues reported via sqlsmith by Andreas Seltenreich

Authors: Pavan Deolasee, Simon Riggs
Reviewer: Peter Geoghegan, Amit Langote, Tomas Vondra, Simon Riggs

Discussion:
https://postgr.es/m/CANP8+jKitBSrB7oTgT9CY2i1ObfOt36z0XMraQc+Xrz8QB0nXA@mail.gmail.com
https://postgr.es/m/CAH2-WzkJdBuxj9PO=2QaO9-3h3xGbQPZ34kJH=HukRekwM-GZg@mail.gmail.com
2018-04-03 09:28:16 +01:00

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/*-------------------------------------------------------------------------
*
* heapam.h
* POSTGRES heap access method definitions.
*
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/access/heapam.h
*
*-------------------------------------------------------------------------
*/
#ifndef HEAPAM_H
#define HEAPAM_H
#include "access/sdir.h"
#include "access/skey.h"
#include "nodes/lockoptions.h"
#include "nodes/primnodes.h"
#include "storage/bufpage.h"
#include "storage/lockdefs.h"
#include "utils/relcache.h"
#include "utils/snapshot.h"
/* "options" flag bits for heap_insert */
#define HEAP_INSERT_SKIP_WAL 0x0001
#define HEAP_INSERT_SKIP_FSM 0x0002
#define HEAP_INSERT_FROZEN 0x0004
#define HEAP_INSERT_SPECULATIVE 0x0008
typedef struct BulkInsertStateData *BulkInsertState;
/*
* Possible lock modes for a tuple.
*/
typedef enum LockTupleMode
{
/* SELECT FOR KEY SHARE */
LockTupleKeyShare,
/* SELECT FOR SHARE */
LockTupleShare,
/* SELECT FOR NO KEY UPDATE, and UPDATEs that don't modify key columns */
LockTupleNoKeyExclusive,
/* SELECT FOR UPDATE, UPDATEs that modify key columns, and DELETE */
LockTupleExclusive
} LockTupleMode;
#define MaxLockTupleMode LockTupleExclusive
/*
* When heap_update, heap_delete, or heap_lock_tuple fail because the target
* tuple is already outdated, they fill in this struct to provide information
* to the caller about what happened.
*
* result is the result of HeapTupleSatisfiesUpdate, leading to the failure.
* It's set to HeapTupleMayBeUpdated when there is no failure.
*
* ctid is the target's ctid link: it is the same as the target's TID if the
* target was deleted, or the location of the replacement tuple if the target
* was updated.
*
* xmax is the outdating transaction's XID. If the caller wants to visit the
* replacement tuple, it must check that this matches before believing the
* replacement is really a match.
*
* cmax is the outdating command's CID, but only when the failure code is
* HeapTupleSelfUpdated (i.e., something in the current transaction outdated
* the tuple); otherwise cmax is zero. (We make this restriction because
* HeapTupleHeaderGetCmax doesn't work for tuples outdated in other
* transactions.)
*
* lockmode is only relevant for callers of heap_update() and is the mode which
* the caller should use in case it needs to lock the updated tuple.
*/
typedef struct HeapUpdateFailureData
{
HTSU_Result result;
ItemPointerData ctid;
TransactionId xmax;
CommandId cmax;
LockTupleMode lockmode;
} HeapUpdateFailureData;
/* ----------------
* function prototypes for heap access method
*
* heap_create, heap_create_with_catalog, and heap_drop_with_catalog
* are declared in catalog/heap.h
* ----------------
*/
/* in heap/heapam.c */
extern Relation relation_open(Oid relationId, LOCKMODE lockmode);
extern Relation try_relation_open(Oid relationId, LOCKMODE lockmode);
extern Relation relation_openrv(const RangeVar *relation, LOCKMODE lockmode);
extern Relation relation_openrv_extended(const RangeVar *relation,
LOCKMODE lockmode, bool missing_ok);
extern void relation_close(Relation relation, LOCKMODE lockmode);
extern Relation heap_open(Oid relationId, LOCKMODE lockmode);
extern Relation heap_openrv(const RangeVar *relation, LOCKMODE lockmode);
extern Relation heap_openrv_extended(const RangeVar *relation,
LOCKMODE lockmode, bool missing_ok);
#define heap_close(r,l) relation_close(r,l)
/* struct definitions appear in relscan.h */
typedef struct HeapScanDescData *HeapScanDesc;
typedef struct ParallelHeapScanDescData *ParallelHeapScanDesc;
/*
* HeapScanIsValid
* True iff the heap scan is valid.
*/
#define HeapScanIsValid(scan) PointerIsValid(scan)
extern HeapScanDesc heap_beginscan(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key);
extern HeapScanDesc heap_beginscan_catalog(Relation relation, int nkeys,
ScanKey key);
extern HeapScanDesc heap_beginscan_strat(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key,
bool allow_strat, bool allow_sync);
extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key);
extern HeapScanDesc heap_beginscan_sampling(Relation relation,
Snapshot snapshot, int nkeys, ScanKey key,
bool allow_strat, bool allow_sync, bool allow_pagemode);
extern void heap_setscanlimits(HeapScanDesc scan, BlockNumber startBlk,
BlockNumber endBlk);
extern void heapgetpage(HeapScanDesc scan, BlockNumber page);
extern void heap_rescan(HeapScanDesc scan, ScanKey key);
extern void heap_rescan_set_params(HeapScanDesc scan, ScanKey key,
bool allow_strat, bool allow_sync, bool allow_pagemode);
extern void heap_endscan(HeapScanDesc scan);
extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);
extern Size heap_parallelscan_estimate(Snapshot snapshot);
extern void heap_parallelscan_initialize(ParallelHeapScanDesc target,
Relation relation, Snapshot snapshot);
extern void heap_parallelscan_reinitialize(ParallelHeapScanDesc parallel_scan);
extern HeapScanDesc heap_beginscan_parallel(Relation, ParallelHeapScanDesc);
extern bool heap_fetch(Relation relation, Snapshot snapshot,
HeapTuple tuple, Buffer *userbuf, bool keep_buf,
Relation stats_relation);
extern bool heap_hot_search_buffer(ItemPointer tid, Relation relation,
Buffer buffer, Snapshot snapshot, HeapTuple heapTuple,
bool *all_dead, bool first_call);
extern bool heap_hot_search(ItemPointer tid, Relation relation,
Snapshot snapshot, bool *all_dead);
extern void heap_get_latest_tid(Relation relation, Snapshot snapshot,
ItemPointer tid);
extern void setLastTid(const ItemPointer tid);
extern BulkInsertState GetBulkInsertState(void);
extern void FreeBulkInsertState(BulkInsertState);
extern void ReleaseBulkInsertStatePin(BulkInsertState bistate);
extern Oid heap_insert(Relation relation, HeapTuple tup, CommandId cid,
int options, BulkInsertState bistate);
extern void heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
CommandId cid, int options, BulkInsertState bistate);
extern HTSU_Result heap_delete(Relation relation, ItemPointer tid,
CommandId cid, Snapshot crosscheck, bool wait,
HeapUpdateFailureData *hufd);
extern void heap_finish_speculative(Relation relation, HeapTuple tuple);
extern void heap_abort_speculative(Relation relation, HeapTuple tuple);
extern HTSU_Result heap_update(Relation relation, ItemPointer otid,
HeapTuple newtup,
CommandId cid, Snapshot crosscheck, bool wait,
HeapUpdateFailureData *hufd);
extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
bool follow_update,
Buffer *buffer, HeapUpdateFailureData *hufd);
extern void heap_inplace_update(Relation relation, HeapTuple tuple);
extern bool heap_freeze_tuple(HeapTupleHeader tuple,
TransactionId relfrozenxid, TransactionId relminmxid,
TransactionId cutoff_xid, TransactionId cutoff_multi);
extern bool heap_tuple_needs_freeze(HeapTupleHeader tuple, TransactionId cutoff_xid,
MultiXactId cutoff_multi, Buffer buf);
extern bool heap_tuple_needs_eventual_freeze(HeapTupleHeader tuple);
extern Oid simple_heap_insert(Relation relation, HeapTuple tup);
extern void simple_heap_delete(Relation relation, ItemPointer tid);
extern void simple_heap_update(Relation relation, ItemPointer otid,
HeapTuple tup);
extern void heap_sync(Relation relation);
extern void heap_update_snapshot(HeapScanDesc scan, Snapshot snapshot);
/* in heap/pruneheap.c */
extern void heap_page_prune_opt(Relation relation, Buffer buffer);
extern int heap_page_prune(Relation relation, Buffer buffer,
TransactionId OldestXmin,
bool report_stats, TransactionId *latestRemovedXid);
extern void heap_page_prune_execute(Buffer buffer,
OffsetNumber *redirected, int nredirected,
OffsetNumber *nowdead, int ndead,
OffsetNumber *nowunused, int nunused);
extern void heap_get_root_tuples(Page page, OffsetNumber *root_offsets);
/* in heap/syncscan.c */
extern void ss_report_location(Relation rel, BlockNumber location);
extern BlockNumber ss_get_location(Relation rel, BlockNumber relnblocks);
extern void SyncScanShmemInit(void);
extern Size SyncScanShmemSize(void);
#endif /* HEAPAM_H */
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