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6bd4f401b0
ReadNewTransactionId from GetSnapshotData --- with a "latestCompletedXid" variable that is updated during transaction commit or abort. Since latestCompletedXid is written only in places that had to lock ProcArrayLock exclusively anyway, and is read only in places that had to lock ProcArrayLock shared anyway, it adds no new locking requirements to the system despite being cluster-wide. Moreover, removing ReadNewTransactionId from snapshot acquisition eliminates the need to take both XidGenLock and ProcArrayLock at the same time. Since XidGenLock is sometimes held across I/O this can be a significant win. Some preliminary benchmarking suggested that this patch has no effect on average throughput but can significantly improve the worst-case transaction times seen in pgbench. Concept by Florian Pflug, implementation by Tom Lane.
189 lines
6.0 KiB
C
189 lines
6.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* xact.h
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* postgres transaction system definitions
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*
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*
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* Portions Copyright (c) 1996-2007, 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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* $PostgreSQL: pgsql/src/include/access/xact.h,v 1.90 2007/09/08 20:31:15 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef XACT_H
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#define XACT_H
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#include "access/xlog.h"
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#include "nodes/pg_list.h"
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#include "storage/relfilenode.h"
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#include "utils/timestamp.h"
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/*
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* Xact isolation levels
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*/
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#define XACT_READ_UNCOMMITTED 0
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#define XACT_READ_COMMITTED 1
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#define XACT_REPEATABLE_READ 2
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#define XACT_SERIALIZABLE 3
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extern int DefaultXactIsoLevel;
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extern int XactIsoLevel;
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/*
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* We only implement two isolation levels internally. This macro should
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* be used to check which one is selected.
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*/
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#define IsXactIsoLevelSerializable (XactIsoLevel >= XACT_REPEATABLE_READ)
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/* Xact read-only state */
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extern bool DefaultXactReadOnly;
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extern bool XactReadOnly;
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/* Asynchronous commits */
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extern bool XactSyncCommit;
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/*
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* start- and end-of-transaction callbacks for dynamically loaded modules
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*/
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typedef enum
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{
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XACT_EVENT_COMMIT,
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XACT_EVENT_ABORT,
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XACT_EVENT_PREPARE
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} XactEvent;
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typedef void (*XactCallback) (XactEvent event, void *arg);
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typedef enum
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{
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SUBXACT_EVENT_START_SUB,
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SUBXACT_EVENT_COMMIT_SUB,
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SUBXACT_EVENT_ABORT_SUB
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} SubXactEvent;
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typedef void (*SubXactCallback) (SubXactEvent event, SubTransactionId mySubid,
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SubTransactionId parentSubid, void *arg);
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/* ----------------
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* transaction-related XLOG entries
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* ----------------
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*/
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/*
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* XLOG allows to store some information in high 4 bits of log
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* record xl_info field
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*/
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#define XLOG_XACT_COMMIT 0x00
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#define XLOG_XACT_PREPARE 0x10
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#define XLOG_XACT_ABORT 0x20
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#define XLOG_XACT_COMMIT_PREPARED 0x30
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#define XLOG_XACT_ABORT_PREPARED 0x40
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typedef struct xl_xact_commit
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{
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TimestampTz xact_time; /* time of commit */
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int nrels; /* number of RelFileNodes */
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int nsubxacts; /* number of subtransaction XIDs */
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/* Array of RelFileNode(s) to drop at commit */
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RelFileNode xnodes[1]; /* VARIABLE LENGTH ARRAY */
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/* ARRAY OF COMMITTED SUBTRANSACTION XIDs FOLLOWS */
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} xl_xact_commit;
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#define MinSizeOfXactCommit offsetof(xl_xact_commit, xnodes)
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typedef struct xl_xact_abort
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{
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TimestampTz xact_time; /* time of abort */
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int nrels; /* number of RelFileNodes */
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int nsubxacts; /* number of subtransaction XIDs */
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/* Array of RelFileNode(s) to drop at abort */
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RelFileNode xnodes[1]; /* VARIABLE LENGTH ARRAY */
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/* ARRAY OF ABORTED SUBTRANSACTION XIDs FOLLOWS */
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} xl_xact_abort;
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#define MinSizeOfXactAbort offsetof(xl_xact_abort, xnodes)
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/*
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* COMMIT_PREPARED and ABORT_PREPARED are identical to COMMIT/ABORT records
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* except that we have to store the XID of the prepared transaction explicitly
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* --- the XID in the record header will be for the transaction doing the
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* COMMIT PREPARED or ABORT PREPARED command.
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*/
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typedef struct xl_xact_commit_prepared
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{
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TransactionId xid; /* XID of prepared xact */
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xl_xact_commit crec; /* COMMIT record */
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/* MORE DATA FOLLOWS AT END OF STRUCT */
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} xl_xact_commit_prepared;
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#define MinSizeOfXactCommitPrepared offsetof(xl_xact_commit_prepared, crec.xnodes)
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typedef struct xl_xact_abort_prepared
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{
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TransactionId xid; /* XID of prepared xact */
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xl_xact_abort arec; /* ABORT record */
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/* MORE DATA FOLLOWS AT END OF STRUCT */
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} xl_xact_abort_prepared;
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#define MinSizeOfXactAbortPrepared offsetof(xl_xact_abort_prepared, arec.xnodes)
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/* ----------------
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* extern definitions
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* ----------------
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*/
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extern bool IsTransactionState(void);
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extern bool IsAbortedTransactionBlockState(void);
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extern TransactionId GetTopTransactionId(void);
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extern TransactionId GetTopTransactionIdIfAny(void);
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extern TransactionId GetCurrentTransactionId(void);
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extern TransactionId GetCurrentTransactionIdIfAny(void);
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extern SubTransactionId GetCurrentSubTransactionId(void);
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extern CommandId GetCurrentCommandId(void);
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extern TimestampTz GetCurrentTransactionStartTimestamp(void);
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extern TimestampTz GetCurrentStatementStartTimestamp(void);
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extern TimestampTz GetCurrentTransactionStopTimestamp(void);
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extern void SetCurrentStatementStartTimestamp(void);
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extern int GetCurrentTransactionNestLevel(void);
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extern bool TransactionIdIsCurrentTransactionId(TransactionId xid);
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extern void CommandCounterIncrement(void);
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extern void ForceSyncCommit(void);
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extern void StartTransactionCommand(void);
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extern void CommitTransactionCommand(void);
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extern void AbortCurrentTransaction(void);
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extern void BeginTransactionBlock(void);
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extern bool EndTransactionBlock(void);
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extern bool PrepareTransactionBlock(char *gid);
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extern void UserAbortTransactionBlock(void);
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extern void ReleaseSavepoint(List *options);
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extern void DefineSavepoint(char *name);
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extern void RollbackToSavepoint(List *options);
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extern void BeginInternalSubTransaction(char *name);
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extern void ReleaseCurrentSubTransaction(void);
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extern void RollbackAndReleaseCurrentSubTransaction(void);
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extern bool IsSubTransaction(void);
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extern bool IsTransactionBlock(void);
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extern bool IsTransactionOrTransactionBlock(void);
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extern char TransactionBlockStatusCode(void);
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extern void AbortOutOfAnyTransaction(void);
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extern void PreventTransactionChain(bool isTopLevel, const char *stmtType);
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extern void RequireTransactionChain(bool isTopLevel, const char *stmtType);
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extern bool IsInTransactionChain(bool isTopLevel);
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extern void RegisterXactCallback(XactCallback callback, void *arg);
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extern void UnregisterXactCallback(XactCallback callback, void *arg);
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extern void RegisterSubXactCallback(SubXactCallback callback, void *arg);
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extern void UnregisterSubXactCallback(SubXactCallback callback, void *arg);
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extern TransactionId RecordTransactionCommit(void);
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extern int xactGetCommittedChildren(TransactionId **ptr);
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extern void xact_redo(XLogRecPtr lsn, XLogRecord *record);
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extern void xact_desc(StringInfo buf, uint8 xl_info, char *rec);
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#endif /* XACT_H */
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