xact.h

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/*-------------------------------------------------------------------------
 *
 * xact.h
 *    postgres transaction system definitions
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/xact.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef XACT_H
#define XACT_H

#include "access/xlog.h"
#include "nodes/pg_list.h"
#include "storage/relfilenode.h"


/*
 * Xact isolation levels
 */
#define XACT_READ_UNCOMMITTED   0
#define XACT_READ_COMMITTED     1
#define XACT_REPEATABLE_READ    2
#define XACT_SERIALIZABLE       3

extern int  DefaultXactIsoLevel;
extern PGDLLIMPORT int XactIsoLevel;

/*
 * We implement three isolation levels internally.
 * The two stronger ones use one snapshot per database transaction;
 * the others use one snapshot per statement.
 * Serializable uses predicate locks in addition to snapshots.
 * These macros should be used to check which isolation level is selected.
 */
#define IsolationUsesXactSnapshot() (XactIsoLevel >= XACT_REPEATABLE_READ)
#define IsolationIsSerializable() (XactIsoLevel == XACT_SERIALIZABLE)

/* Xact read-only state */
extern bool DefaultXactReadOnly;
extern bool XactReadOnly;

/*
 * Xact is deferrable -- only meaningful (currently) for read only
 * SERIALIZABLE transactions
 */
extern bool DefaultXactDeferrable;
extern bool XactDeferrable;

typedef enum
{
    SYNCHRONOUS_COMMIT_OFF,     /* asynchronous commit */
    SYNCHRONOUS_COMMIT_LOCAL_FLUSH,     /* wait for local flush only */
    SYNCHRONOUS_COMMIT_REMOTE_WRITE,    /* wait for local flush and remote
                                         * write */
    SYNCHRONOUS_COMMIT_REMOTE_FLUSH     /* wait for local and remote flush */
}   SyncCommitLevel;

/* Define the default setting for synchonous_commit */
#define SYNCHRONOUS_COMMIT_ON   SYNCHRONOUS_COMMIT_REMOTE_FLUSH

/* Synchronous commit level */
extern int  synchronous_commit;

/* Kluge for 2PC support */
extern bool MyXactAccessedTempRel;

/*
 *  start- and end-of-transaction callbacks for dynamically loaded modules
 */
typedef enum
{
    XACT_EVENT_COMMIT,
    XACT_EVENT_ABORT,
    XACT_EVENT_PREPARE,
    XACT_EVENT_PRE_COMMIT,
    XACT_EVENT_PRE_PREPARE
} XactEvent;

typedef void (*XactCallback) (XactEvent event, void *arg);

typedef enum
{
    SUBXACT_EVENT_START_SUB,
    SUBXACT_EVENT_COMMIT_SUB,
    SUBXACT_EVENT_ABORT_SUB,
    SUBXACT_EVENT_PRE_COMMIT_SUB
} SubXactEvent;

typedef void (*SubXactCallback) (SubXactEvent event, SubTransactionId mySubid,
                                    SubTransactionId parentSubid, void *arg);


/* ----------------
 *      transaction-related XLOG entries
 * ----------------
 */

/*
 * XLOG allows to store some information in high 4 bits of log
 * record xl_info field
 */
#define XLOG_XACT_COMMIT            0x00
#define XLOG_XACT_PREPARE           0x10
#define XLOG_XACT_ABORT             0x20
#define XLOG_XACT_COMMIT_PREPARED   0x30
#define XLOG_XACT_ABORT_PREPARED    0x40
#define XLOG_XACT_ASSIGNMENT        0x50
#define XLOG_XACT_COMMIT_COMPACT    0x60

typedef struct xl_xact_assignment
{
    TransactionId xtop;         /* assigned XID's top-level XID */
    int         nsubxacts;      /* number of subtransaction XIDs */
    TransactionId xsub[1];      /* assigned subxids */
} xl_xact_assignment;

#define MinSizeOfXactAssignment offsetof(xl_xact_assignment, xsub)

typedef struct xl_xact_commit_compact
{
    TimestampTz xact_time;      /* time of commit */
    int         nsubxacts;      /* number of subtransaction XIDs */
    /* ARRAY OF COMMITTED SUBTRANSACTION XIDs FOLLOWS */
    TransactionId subxacts[1];  /* VARIABLE LENGTH ARRAY */
} xl_xact_commit_compact;

#define MinSizeOfXactCommitCompact offsetof(xl_xact_commit_compact, subxacts)

typedef struct xl_xact_commit
{
    TimestampTz xact_time;      /* time of commit */
    uint32      xinfo;          /* info flags */
    int         nrels;          /* number of RelFileNodes */
    int         nsubxacts;      /* number of subtransaction XIDs */
    int         nmsgs;          /* number of shared inval msgs */
    Oid         dbId;           /* MyDatabaseId */
    Oid         tsId;           /* MyDatabaseTableSpace */
    /* Array of RelFileNode(s) to drop at commit */
    RelFileNode xnodes[1];      /* VARIABLE LENGTH ARRAY */
    /* ARRAY OF COMMITTED SUBTRANSACTION XIDs FOLLOWS */
    /* ARRAY OF SHARED INVALIDATION MESSAGES FOLLOWS */
} xl_xact_commit;

#define MinSizeOfXactCommit offsetof(xl_xact_commit, xnodes)

/*
 * These flags are set in the xinfo fields of WAL commit records,
 * indicating a variety of additional actions that need to occur
 * when emulating transaction effects during recovery.
 * They are named XactCompletion... to differentiate them from
 * EOXact... routines which run at the end of the original
 * transaction completion.
 */
#define XACT_COMPLETION_UPDATE_RELCACHE_FILE    0x01
#define XACT_COMPLETION_FORCE_SYNC_COMMIT       0x02

/* Access macros for above flags */
#define XactCompletionRelcacheInitFileInval(xinfo)  (xinfo & XACT_COMPLETION_UPDATE_RELCACHE_FILE)
#define XactCompletionForceSyncCommit(xinfo)        (xinfo & XACT_COMPLETION_FORCE_SYNC_COMMIT)

typedef struct xl_xact_abort
{
    TimestampTz xact_time;      /* time of abort */
    int         nrels;          /* number of RelFileNodes */
    int         nsubxacts;      /* number of subtransaction XIDs */
    /* Array of RelFileNode(s) to drop at abort */
    RelFileNode xnodes[1];      /* VARIABLE LENGTH ARRAY */
    /* ARRAY OF ABORTED SUBTRANSACTION XIDs FOLLOWS */
} xl_xact_abort;

/* Note the intentional lack of an invalidation message array c.f. commit */

#define MinSizeOfXactAbort offsetof(xl_xact_abort, xnodes)

/*
 * COMMIT_PREPARED and ABORT_PREPARED are identical to COMMIT/ABORT records
 * except that we have to store the XID of the prepared transaction explicitly
 * --- the XID in the record header will be for the transaction doing the
 * COMMIT PREPARED or ABORT PREPARED command.
 */

typedef struct xl_xact_commit_prepared
{
    TransactionId xid;          /* XID of prepared xact */
    xl_xact_commit crec;        /* COMMIT record */
    /* MORE DATA FOLLOWS AT END OF STRUCT */
} xl_xact_commit_prepared;

#define MinSizeOfXactCommitPrepared offsetof(xl_xact_commit_prepared, crec.xnodes)

typedef struct xl_xact_abort_prepared
{
    TransactionId xid;          /* XID of prepared xact */
    xl_xact_abort arec;         /* ABORT record */
    /* MORE DATA FOLLOWS AT END OF STRUCT */
} xl_xact_abort_prepared;

#define MinSizeOfXactAbortPrepared offsetof(xl_xact_abort_prepared, arec.xnodes)


/* ----------------
 *      extern definitions
 * ----------------
 */
extern bool IsTransactionState(void);
extern bool IsAbortedTransactionBlockState(void);
extern TransactionId GetTopTransactionId(void);
extern TransactionId GetTopTransactionIdIfAny(void);
extern TransactionId GetCurrentTransactionId(void);
extern TransactionId GetCurrentTransactionIdIfAny(void);
extern TransactionId GetStableLatestTransactionId(void);
extern SubTransactionId GetCurrentSubTransactionId(void);
extern bool SubTransactionIsActive(SubTransactionId subxid);
extern CommandId GetCurrentCommandId(bool used);
extern TimestampTz GetCurrentTransactionStartTimestamp(void);
extern TimestampTz GetCurrentStatementStartTimestamp(void);
extern TimestampTz GetCurrentTransactionStopTimestamp(void);
extern void SetCurrentStatementStartTimestamp(void);
extern int  GetCurrentTransactionNestLevel(void);
extern bool TransactionIdIsCurrentTransactionId(TransactionId xid);
extern void CommandCounterIncrement(void);
extern void ForceSyncCommit(void);
extern void StartTransactionCommand(void);
extern void CommitTransactionCommand(void);
extern void AbortCurrentTransaction(void);
extern void BeginTransactionBlock(void);
extern bool EndTransactionBlock(void);
extern bool PrepareTransactionBlock(char *gid);
extern void UserAbortTransactionBlock(void);
extern void ReleaseSavepoint(List *options);
extern void DefineSavepoint(char *name);
extern void RollbackToSavepoint(List *options);
extern void BeginInternalSubTransaction(char *name);
extern void ReleaseCurrentSubTransaction(void);
extern void RollbackAndReleaseCurrentSubTransaction(void);
extern bool IsSubTransaction(void);
extern bool IsTransactionBlock(void);
extern bool IsTransactionOrTransactionBlock(void);
extern char TransactionBlockStatusCode(void);
extern void AbortOutOfAnyTransaction(void);
extern void PreventTransactionChain(bool isTopLevel, const char *stmtType);
extern void RequireTransactionChain(bool isTopLevel, const char *stmtType);
extern bool IsInTransactionChain(bool isTopLevel);
extern void RegisterXactCallback(XactCallback callback, void *arg);
extern void UnregisterXactCallback(XactCallback callback, void *arg);
extern void RegisterSubXactCallback(SubXactCallback callback, void *arg);
extern void UnregisterSubXactCallback(SubXactCallback callback, void *arg);

extern int  xactGetCommittedChildren(TransactionId **ptr);

extern void xact_redo(XLogRecPtr lsn, XLogRecord *record);
extern void xact_desc(StringInfo buf, uint8 xl_info, char *rec);

#endif   /* XACT_H */