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2c03216d83
Each WAL record now carries information about the modified relation and block(s) in a standardized format. That makes it easier to write tools that need that information, like pg_rewind, prefetching the blocks to speed up recovery, etc. There's a whole new API for building WAL records, replacing the XLogRecData chains used previously. The new API consists of XLogRegister* functions, which are called for each buffer and chunk of data that is added to the record. The new API also gives more control over when a full-page image is written, by passing flags to the XLogRegisterBuffer function. This also simplifies the XLogReadBufferForRedo() calls. The function can dig the relation and block number from the WAL record, so they no longer need to be passed as arguments. For the convenience of redo routines, XLogReader now disects each WAL record after reading it, copying the main data part and the per-block data into MAXALIGNed buffers. The data chunks are not aligned within the WAL record, but the redo routines can assume that the pointers returned by XLogRecGet* functions are. Redo routines are now passed the XLogReaderState, which contains the record in the already-disected format, instead of the plain XLogRecord. The new record format also makes the fixed size XLogRecord header smaller, by removing the xl_len field. The length of the "main data" portion is now stored at the end of the WAL record, and there's a separate header after XLogRecord for it. The alignment padding at the end of XLogRecord is also removed. This compansates for the fact that the new format would otherwise be more bulky than the old format. Reviewed by Andres Freund, Amit Kapila, Michael Paquier, Alvaro Herrera, Fujii Masao.
56 lines
1.5 KiB
C
56 lines
1.5 KiB
C
/*
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* clog.h
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*
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* PostgreSQL transaction-commit-log manager
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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/clog.h
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*/
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#ifndef CLOG_H
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#define CLOG_H
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#include "access/xlogreader.h"
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#include "lib/stringinfo.h"
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/*
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* Possible transaction statuses --- note that all-zeroes is the initial
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* state.
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*
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* A "subcommitted" transaction is a committed subtransaction whose parent
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* hasn't committed or aborted yet.
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*/
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typedef int XidStatus;
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#define TRANSACTION_STATUS_IN_PROGRESS 0x00
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#define TRANSACTION_STATUS_COMMITTED 0x01
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#define TRANSACTION_STATUS_ABORTED 0x02
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#define TRANSACTION_STATUS_SUB_COMMITTED 0x03
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extern void TransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
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TransactionId *subxids, XidStatus status, XLogRecPtr lsn);
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extern XidStatus TransactionIdGetStatus(TransactionId xid, XLogRecPtr *lsn);
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extern Size CLOGShmemBuffers(void);
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extern Size CLOGShmemSize(void);
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extern void CLOGShmemInit(void);
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extern void BootStrapCLOG(void);
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extern void StartupCLOG(void);
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extern void TrimCLOG(void);
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extern void ShutdownCLOG(void);
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extern void CheckPointCLOG(void);
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extern void ExtendCLOG(TransactionId newestXact);
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extern void TruncateCLOG(TransactionId oldestXact);
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/* XLOG stuff */
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#define CLOG_ZEROPAGE 0x00
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#define CLOG_TRUNCATE 0x10
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extern void clog_redo(XLogReaderState *record);
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extern void clog_desc(StringInfo buf, XLogReaderState *record);
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extern const char *clog_identify(uint8 info);
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#endif /* CLOG_H */
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