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/*-------------------------------------------------------------------------
*
* xlogreader.h
* Definitions for the generic XLog reading facility
*
* Portions Copyright (c) 2013-2015, 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) */
char *readBuf;
/* last read segment, segment offset, read length, TLI */
XLogSegNo readSegNo;
uint32 readOff;
uint32 readLen;
TimeLineID readPageTLI;
/* beginning of last page read, and its TLI */
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;
};
/* 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);
#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 */
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