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/*------------------------------------------------------------------------- * * xlogreader.h * Definitions for the generic XLog reading facility * * Portions Copyright (c) 2013-2016, PostgreSQL Global Development Group * * IDENTIFICATION * src/include/access/xlogreader.h * * NOTES * See the definition of the XLogReaderState struct for instructions on * how to use the XLogReader infrastructure. * * The basic idea is to allocate an XLogReaderState via * XLogReaderAllocate(), and call XLogReadRecord() until it returns NULL. * * After reading a record with XLogReadRecord(), it's decomposed into * the per-block and main data parts, and the parts can be accessed * with the XLogRec* macros and functions. You can also decode a * record that's already constructed in memory, without reading from * disk, by calling the DecodeXLogRecord() function. *------------------------------------------------------------------------- */ #ifndef XLOGREADER_H #define XLOGREADER_H #include "access/xlogrecord.h" typedef struct XLogReaderState XLogReaderState; /* Function type definition for the read_page callback */ typedef int (*XLogPageReadCB) (XLogReaderState *xlogreader, XLogRecPtr targetPagePtr, int reqLen, XLogRecPtr targetRecPtr, char *readBuf, TimeLineID *pageTLI); typedef struct { /* Is this block ref in use? */ bool in_use; /* Identify the block this refers to */ RelFileNode rnode; ForkNumber forknum; BlockNumber blkno; /* copy of the fork_flags field from the XLogRecordBlockHeader */ uint8 flags; /* Information on full-page image, if any */ bool has_image; char *bkp_image; uint16 hole_offset; uint16 hole_length; uint16 bimg_len; uint8 bimg_info; /* Buffer holding the rmgr-specific data associated with this block */ bool has_data; char *data; uint16 data_len; uint16 data_bufsz; } DecodedBkpBlock; struct XLogReaderState { /* ---------------------------------------- * Public parameters * ---------------------------------------- */ /* * Data input callback (mandatory). * * This callback shall read at least reqLen valid bytes of the xlog page * starting at targetPagePtr, and store them in readBuf. The callback * shall return the number of bytes read (never more than XLOG_BLCKSZ), or * -1 on failure. The callback shall sleep, if necessary, to wait for the * requested bytes to become available. The callback will not be invoked * again for the same page unless more than the returned number of bytes * are needed. * * targetRecPtr is the position of the WAL record we're reading. Usually * it is equal to targetPagePtr + reqLen, but sometimes xlogreader needs * to read and verify the page or segment header, before it reads the * actual WAL record it's interested in. In that case, targetRecPtr can * be used to determine which timeline to read the page from. * * The callback shall set *pageTLI to the TLI of the file the page was * read from. It is currently used only for error reporting purposes, to * reconstruct the name of the WAL file where an error occurred. */ XLogPageReadCB read_page; /* * System identifier of the xlog files we're about to read. Set to zero * (the default value) if unknown or unimportant. */ uint64 system_identifier; /* * Opaque data for callbacks to use. Not used by XLogReader. */ void *private_data; /* * Start and end point of last record read. EndRecPtr is also used as the * position to read next, if XLogReadRecord receives an invalid recptr. */ XLogRecPtr ReadRecPtr; /* start of last record read */ XLogRecPtr EndRecPtr; /* end+1 of last record read */ /* ---------------------------------------- * Decoded representation of current record * * Use XLogRecGet* functions to investigate the record; these fields * should not be accessed directly. * ---------------------------------------- */ XLogRecord *decoded_record; /* currently decoded record */ char *main_data; /* record's main data portion */ uint32 main_data_len; /* main data portion's length */ uint32 main_data_bufsz; /* allocated size of the buffer */ RepOriginId record_origin; /* information about blocks referenced by the record. */ DecodedBkpBlock blocks[XLR_MAX_BLOCK_ID + 1]; int max_block_id; /* highest block_id in use (-1 if none) */ /* ---------------------------------------- * private/internal state * ---------------------------------------- */ /* * Buffer for currently read page (XLOG_BLCKSZ bytes, valid up to at least * readLen bytes) */ char *readBuf; uint32 readLen; /* last read segment, segment offset, TLI for data currently in readBuf */ XLogSegNo readSegNo; uint32 readOff; TimeLineID readPageTLI; /* * beginning of prior page read, and its TLI. Doesn't necessarily * correspond to what's in readBuf; used for timeline sanity checks. */ XLogRecPtr latestPagePtr; TimeLineID latestPageTLI; /* beginning of the WAL record being read. */ XLogRecPtr currRecPtr; /* Buffer for current ReadRecord result (expandable) */ char *readRecordBuf; uint32 readRecordBufSize; /* Buffer to hold error message */ char *errormsg_buf; /* * Set at the end of recovery: the start point of a partial record at the * end of WAL (InvalidXLogRecPtr if there wasn't one), and the start * location of its first contrecord that went missing. */ XLogRecPtr abortedRecPtr; XLogRecPtr missingContrecPtr; /* Set when XLP_FIRST_IS_OVERWRITE_CONTRECORD is found */ XLogRecPtr overwrittenRecPtr; }; /* Get a new XLogReader */ extern XLogReaderState *XLogReaderAllocate(XLogPageReadCB pagereadfunc, void *private_data); /* Free an XLogReader */ extern void XLogReaderFree(XLogReaderState *state); /* Read the next XLog record. Returns NULL on end-of-WAL or failure */ extern struct XLogRecord *XLogReadRecord(XLogReaderState *state, XLogRecPtr recptr, char **errormsg); /* Validate a page */ extern bool XLogReaderValidatePageHeader(XLogReaderState *state, XLogRecPtr recptr, char *phdr); /* Invalidate read state */ extern void XLogReaderInvalReadState(XLogReaderState *state); #ifdef FRONTEND extern XLogRecPtr XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr); #endif /* FRONTEND */ /* Functions for decoding an XLogRecord */ extern bool DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errmsg); #define XLogRecGetTotalLen(decoder) ((decoder)->decoded_record->xl_tot_len) #define XLogRecGetPrev(decoder) ((decoder)->decoded_record->xl_prev) #define XLogRecGetInfo(decoder) ((decoder)->decoded_record->xl_info) #define XLogRecGetRmid(decoder) ((decoder)->decoded_record->xl_rmid) #define XLogRecGetXid(decoder) ((decoder)->decoded_record->xl_xid) #define XLogRecGetOrigin(decoder) ((decoder)->record_origin) #define XLogRecGetData(decoder) ((decoder)->main_data) #define XLogRecGetDataLen(decoder) ((decoder)->main_data_len) #define XLogRecHasAnyBlockRefs(decoder) ((decoder)->max_block_id >= 0) #define XLogRecHasBlockRef(decoder, block_id) \ ((decoder)->blocks[block_id].in_use) #define XLogRecHasBlockImage(decoder, block_id) \ ((decoder)->blocks[block_id].has_image) extern bool RestoreBlockImage(XLogReaderState *recoder, uint8 block_id, char *dst); extern char *XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len); extern bool XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id, RelFileNode *rnode, ForkNumber *forknum, BlockNumber *blknum); #endif /* XLOGREADER_H */