xact.h

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * xact.h
 *    postgres transaction system definitions
 *
 *
 * Portions Copyright (c) 1996-2018, 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/xlogreader.h"
#include "lib/stringinfo.h"
#include "nodes/pg_list.h"
#include "storage/relfilenode.h"
#include "storage/sinval.h"
#include "utils/datetime.h"

/*
 * Maximum size of Global Transaction ID (including '\0').
 *
 * Note that the max value of GIDSIZE must fit in the uint16 gidlen,
 * specified in TwoPhaseFileHeader.
 */
#define GIDSIZE 200

/*
 * 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 */
    SYNCHRONOUS_COMMIT_REMOTE_APPLY /* wait for local flush and remote apply */
}           SyncCommitLevel;

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

/* Synchronous commit level */
extern int  synchronous_commit;

/*
 * Miscellaneous flag bits to record events which occur on the top level
 * transaction. These flags are only persisted in MyXactFlags and are intended
 * so we remember to do certain things later in the transaction. This is
 * globally accessible, so can be set from anywhere in the code which requires
 * recording flags.
 */
extern int  MyXactFlags;

/*
 * XACT_FLAGS_ACCESSEDTEMPREL - set when a temporary relation is accessed. We
 * don't allow PREPARE TRANSACTION in that case.
 */
#define XACT_FLAGS_ACCESSEDTEMPREL              (1U << 0)

/*
 * XACT_FLAGS_ACQUIREDACCESSEXCLUSIVELOCK - records whether the top level xact
 * logged any Access Exclusive Locks.
 */
#define XACT_FLAGS_ACQUIREDACCESSEXCLUSIVELOCK  (1U << 1)


/*
 *  start- and end-of-transaction callbacks for dynamically loaded modules
 */
typedef enum
{
    XACT_EVENT_COMMIT,
    XACT_EVENT_PARALLEL_COMMIT,
    XACT_EVENT_ABORT,
    XACT_EVENT_PARALLEL_ABORT,
    XACT_EVENT_PREPARE,
    XACT_EVENT_PRE_COMMIT,
    XACT_EVENT_PARALLEL_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. We use 3 for the opcode, and one about an optional flag variable.
 */
#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
/* free opcode 0x60 */
/* free opcode 0x70 */

/* mask for filtering opcodes out of xl_info */
#define XLOG_XACT_OPMASK            0x70

/* does this record have a 'xinfo' field or not */
#define XLOG_XACT_HAS_INFO          0x80

/*
 * The following flags, stored in xinfo, determine which information is
 * contained in commit/abort records.
 */
#define XACT_XINFO_HAS_DBINFO           (1U << 0)
#define XACT_XINFO_HAS_SUBXACTS         (1U << 1)
#define XACT_XINFO_HAS_RELFILENODES     (1U << 2)
#define XACT_XINFO_HAS_INVALS           (1U << 3)
#define XACT_XINFO_HAS_TWOPHASE         (1U << 4)
#define XACT_XINFO_HAS_ORIGIN           (1U << 5)
#define XACT_XINFO_HAS_AE_LOCKS         (1U << 6)
#define XACT_XINFO_HAS_GID              (1U << 7)

/*
 * Also stored in xinfo, these 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_APPLY_FEEDBACK          (1U << 29)
#define XACT_COMPLETION_UPDATE_RELCACHE_FILE    (1U << 30)
#define XACT_COMPLETION_FORCE_SYNC_COMMIT       (1U << 31)

/* Access macros for above flags */
#define XactCompletionApplyFeedback(xinfo) \
    ((xinfo & XACT_COMPLETION_APPLY_FEEDBACK) != 0)
#define XactCompletionRelcacheInitFileInval(xinfo) \
    ((xinfo & XACT_COMPLETION_UPDATE_RELCACHE_FILE) != 0)
#define XactCompletionForceSyncCommit(xinfo) \
    ((xinfo & XACT_COMPLETION_FORCE_SYNC_COMMIT) != 0)

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

#define MinSizeOfXactAssignment offsetof(xl_xact_assignment, xsub)

/*
 * Commit and abort records can contain a lot of information. But a large
 * portion of the records won't need all possible pieces of information. So we
 * only include what's needed.
 *
 * A minimal commit/abort record only consists of a xl_xact_commit/abort
 * struct. The presence of additional information is indicated by bits set in
 * 'xl_xact_xinfo->xinfo'. The presence of the xinfo field itself is signalled
 * by a set XLOG_XACT_HAS_INFO bit in the xl_info field.
 *
 * NB: All the individual data chunks should be sized to multiples of
 * sizeof(int) and only require int32 alignment. If they require bigger
 * alignment, they need to be copied upon reading.
 */

/* sub-records for commit/abort */

typedef struct xl_xact_xinfo
{
    /*
     * Even though we right now only require 1 byte of space in xinfo we use
     * four so following records don't have to care about alignment. Commit
     * records can be large, so copying large portions isn't attractive.
     */
    uint32      xinfo;
} xl_xact_xinfo;

typedef struct xl_xact_dbinfo
{
    Oid         dbId;           /* MyDatabaseId */
    Oid         tsId;           /* MyDatabaseTableSpace */
} xl_xact_dbinfo;

typedef struct xl_xact_subxacts
{
    int         nsubxacts;      /* number of subtransaction XIDs */
    TransactionId subxacts[FLEXIBLE_ARRAY_MEMBER];
} xl_xact_subxacts;
#define MinSizeOfXactSubxacts offsetof(xl_xact_subxacts, subxacts)

typedef struct xl_xact_relfilenodes
{
    int         nrels;          /* number of subtransaction XIDs */
    RelFileNode xnodes[FLEXIBLE_ARRAY_MEMBER];
} xl_xact_relfilenodes;
#define MinSizeOfXactRelfilenodes offsetof(xl_xact_relfilenodes, xnodes)

typedef struct xl_xact_invals
{
    int         nmsgs;          /* number of shared inval msgs */
    SharedInvalidationMessage msgs[FLEXIBLE_ARRAY_MEMBER];
} xl_xact_invals;
#define MinSizeOfXactInvals offsetof(xl_xact_invals, msgs)

typedef struct xl_xact_twophase
{
    TransactionId xid;
} xl_xact_twophase;

typedef struct xl_xact_origin
{
    XLogRecPtr  origin_lsn;
    TimestampTz origin_timestamp;
} xl_xact_origin;

typedef struct xl_xact_commit
{
    TimestampTz xact_time;      /* time of commit */

    /* xl_xact_xinfo follows if XLOG_XACT_HAS_INFO */
    /* xl_xact_dbinfo follows if XINFO_HAS_DBINFO */
    /* xl_xact_subxacts follows if XINFO_HAS_SUBXACT */
    /* xl_xact_relfilenodes follows if XINFO_HAS_RELFILENODES */
    /* xl_xact_invals follows if XINFO_HAS_INVALS */
    /* xl_xact_twophase follows if XINFO_HAS_TWOPHASE */
    /* twophase_gid follows if XINFO_HAS_GID. As a null-terminated string. */
    /* xl_xact_origin follows if XINFO_HAS_ORIGIN, stored unaligned! */
} xl_xact_commit;
#define MinSizeOfXactCommit (offsetof(xl_xact_commit, xact_time) + sizeof(TimestampTz))

typedef struct xl_xact_abort
{
    TimestampTz xact_time;      /* time of abort */

    /* xl_xact_xinfo follows if XLOG_XACT_HAS_INFO */
    /* xl_xact_dbinfo follows if XINFO_HAS_DBINFO */
    /* xl_xact_subxacts follows if HAS_SUBXACT */
    /* xl_xact_relfilenodes follows if HAS_RELFILENODES */
    /* No invalidation messages needed. */
    /* xl_xact_twophase follows if XINFO_HAS_TWOPHASE */
    /* twophase_gid follows if XINFO_HAS_GID. As a null-terminated string. */
    /* xl_xact_origin follows if XINFO_HAS_ORIGIN, stored unaligned! */
} xl_xact_abort;
#define MinSizeOfXactAbort sizeof(xl_xact_abort)

/*
 * Commit/Abort records in the above form are a bit verbose to parse, so
 * there's a deconstructed versions generated by ParseCommit/AbortRecord() for
 * easier consumption.
 */
typedef struct xl_xact_parsed_commit
{
    TimestampTz xact_time;
    uint32      xinfo;

    Oid         dbId;           /* MyDatabaseId */
    Oid         tsId;           /* MyDatabaseTableSpace */

    int         nsubxacts;
    TransactionId *subxacts;

    int         nrels;
    RelFileNode *xnodes;

    int         nmsgs;
    SharedInvalidationMessage *msgs;

    TransactionId twophase_xid; /* only for 2PC */
    char        twophase_gid[GIDSIZE];  /* only for 2PC */
    int         nabortrels;     /* only for 2PC */
    RelFileNode *abortnodes;    /* only for 2PC */

    XLogRecPtr  origin_lsn;
    TimestampTz origin_timestamp;
} xl_xact_parsed_commit;

typedef xl_xact_parsed_commit xl_xact_parsed_prepare;

typedef struct xl_xact_parsed_abort
{
    TimestampTz xact_time;
    uint32      xinfo;

    Oid         dbId;           /* MyDatabaseId */
    Oid         tsId;           /* MyDatabaseTableSpace */

    int         nsubxacts;
    TransactionId *subxacts;

    int         nrels;
    RelFileNode *xnodes;

    TransactionId twophase_xid; /* only for 2PC */
    char        twophase_gid[GIDSIZE];  /* only for 2PC */

    XLogRecPtr  origin_lsn;
    TimestampTz origin_timestamp;
} xl_xact_parsed_abort;


/* ----------------
 *      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 void MarkCurrentTransactionIdLoggedIfAny(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(const char *gid);
extern void UserAbortTransactionBlock(void);
extern void BeginImplicitTransactionBlock(void);
extern void EndImplicitTransactionBlock(void);
extern void ReleaseSavepoint(const char *name);
extern void DefineSavepoint(const char *name);
extern void RollbackToSavepoint(const char *name);
extern void BeginInternalSubTransaction(const char *name);
extern void ReleaseCurrentSubTransaction(void);
extern void RollbackAndReleaseCurrentSubTransaction(void);
extern bool IsSubTransaction(void);
extern Size EstimateTransactionStateSpace(void);
extern void SerializeTransactionState(Size maxsize, char *start_address);
extern void StartParallelWorkerTransaction(char *tstatespace);
extern void EndParallelWorkerTransaction(void);
extern bool IsTransactionBlock(void);
extern bool IsTransactionOrTransactionBlock(void);
extern char TransactionBlockStatusCode(void);
extern void AbortOutOfAnyTransaction(void);
extern void PreventInTransactionBlock(bool isTopLevel, const char *stmtType);
extern void RequireTransactionBlock(bool isTopLevel, const char *stmtType);
extern void WarnNoTransactionBlock(bool isTopLevel, const char *stmtType);
extern bool IsInTransactionBlock(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 XLogRecPtr XactLogCommitRecord(TimestampTz commit_time,
                    int nsubxacts, TransactionId *subxacts,
                    int nrels, RelFileNode *rels,
                    int nmsgs, SharedInvalidationMessage *msgs,
                    bool relcacheInval, bool forceSync,
                    int xactflags,
                    TransactionId twophase_xid,
                    const char *twophase_gid);

extern XLogRecPtr XactLogAbortRecord(TimestampTz abort_time,
                   int nsubxacts, TransactionId *subxacts,
                   int nrels, RelFileNode *rels,
                   int xactflags, TransactionId twophase_xid,
                   const char *twophase_gid);
extern void xact_redo(XLogReaderState *record);

/* xactdesc.c */
extern void xact_desc(StringInfo buf, XLogReaderState *record);
extern const char *xact_identify(uint8 info);

/* also in xactdesc.c, so they can be shared between front/backend code */
extern void ParseCommitRecord(uint8 info, xl_xact_commit *xlrec, xl_xact_parsed_commit *parsed);
extern void ParseAbortRecord(uint8 info, xl_xact_abort *xlrec, xl_xact_parsed_abort *parsed);

extern void EnterParallelMode(void);
extern void ExitParallelMode(void);
extern bool IsInParallelMode(void);

#endif                          /* XACT_H */