diff options
Diffstat (limited to 'src/include/access/xlogreader.h')
| -rw-r--r-- | src/include/access/xlogreader.h | 153 |
1 files changed, 78 insertions, 75 deletions
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h index 21d200d3df6..d27c0cd281c 100644 --- a/src/include/access/xlogreader.h +++ b/src/include/access/xlogreader.h @@ -56,65 +56,17 @@ typedef struct WALSegmentContext } WALSegmentContext; typedef struct XLogReaderState XLogReaderState; +typedef struct XLogFindNextRecordState XLogFindNextRecordState; -/* Function type definitions for various xlogreader interactions */ -typedef int (*XLogPageReadCB) (XLogReaderState *xlogreader, - XLogRecPtr targetPagePtr, - int reqLen, - XLogRecPtr targetRecPtr, - char *readBuf); +/* Function type definition for the segment cleanup callback */ +typedef void (*WALSegmentCleanupCB) (XLogReaderState *xlogreader); + +/* Function type definition for the open/close callbacks for WALRead() */ typedef void (*WALSegmentOpenCB) (XLogReaderState *xlogreader, XLogSegNo nextSegNo, TimeLineID *tli_p); typedef void (*WALSegmentCloseCB) (XLogReaderState *xlogreader); -typedef struct XLogReaderRoutine -{ - /* - * Data input callback - * - * 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 ->seg.ws_tli to the TLI of the file the page was - * read from. - */ - XLogPageReadCB page_read; - - /* - * Callback to open the specified WAL segment for reading. ->seg.ws_file - * shall be set to the file descriptor of the opened segment. In case of - * failure, an error shall be raised by the callback and it shall not - * return. - * - * "nextSegNo" is the number of the segment to be opened. - * - * "tli_p" is an input/output argument. WALRead() uses it to pass the - * timeline in which the new segment should be found, but the callback can - * use it to return the TLI that it actually opened. - */ - WALSegmentOpenCB segment_open; - - /* - * WAL segment close callback. ->seg.ws_file shall be set to a negative - * number. - */ - WALSegmentCloseCB segment_close; -} XLogReaderRoutine; - -#define XL_ROUTINE(...) &(XLogReaderRoutine){__VA_ARGS__} - typedef struct { /* Is this block ref in use? */ @@ -144,12 +96,36 @@ typedef struct uint16 data_bufsz; } DecodedBkpBlock; +/* Return code from XLogReadRecord */ +typedef enum XLogReadRecordResult +{ + XLREAD_SUCCESS, /* record is successfully read */ + XLREAD_NEED_DATA, /* need more data. see XLogReadRecord. */ + XLREAD_FAIL /* failed during reading a record */ +} XLogReadRecordResult; + +/* + * internal state of XLogReadRecord + * + * XLogReadState runs a state machine while reading a record. Theses states + * are not seen outside the function. Each state may repeat several times + * exiting requesting caller for new data. See the comment of XLogReadRecrod + * for details. + */ +typedef enum XLogReadRecordState +{ + XLREAD_NEXT_RECORD, + XLREAD_TOT_LEN, + XLREAD_FIRST_FRAGMENT, + XLREAD_CONTINUATION +} XLogReadRecordState; + struct XLogReaderState { /* * Operational callbacks */ - XLogReaderRoutine routine; + WALSegmentCleanupCB cleanup_cb; /* ---------------------------------------- * Public parameters @@ -163,18 +139,30 @@ struct XLogReaderState 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. Calling XLogBeginRead() sets EndRecPtr to the * starting position and ReadRecPtr to invalid. */ - XLogRecPtr ReadRecPtr; /* start of last record read */ + XLogRecPtr ReadRecPtr; /* start of last record read or being read */ XLogRecPtr EndRecPtr; /* end+1 of last record read */ + XLogRecPtr PrevRecPtr; /* start of previous record read */ + /* ---------------------------------------- + * Communication with page reader + * readBuf is XLOG_BLCKSZ bytes, valid up to at least reqLen bytes. + * ---------------------------------------- + */ + /* variables the clients of xlogreader can examine */ + XLogRecPtr readPagePtr; /* page pointer to read */ + int32 reqLen; /* bytes requested to the caller */ + char *readBuf; /* buffer to store data */ + bool page_verified; /* is the page header on the buffer verified? */ + bool record_verified;/* is the current record header verified? */ + + /* variables set by the client of xlogreader */ + int32 readLen; /* actual bytes copied into readBuf by client, + * which should be >= reqLen. Client should + * use XLogReaderSetInputData() to set. */ /* ---------------------------------------- * Decoded representation of current record @@ -203,13 +191,6 @@ struct XLogReaderState * ---------------------------------------- */ - /* - * Buffer for currently read page (XLOG_BLCKSZ bytes, valid up to at least - * readLen bytes) - */ - char *readBuf; - uint32 readLen; - /* last read XLOG position for data currently in readBuf */ WALSegmentContext segcxt; WALOpenSegment seg; @@ -222,8 +203,6 @@ struct XLogReaderState XLogRecPtr latestPagePtr; TimeLineID latestPageTLI; - /* beginning of the WAL record being read. */ - XLogRecPtr currRecPtr; /* timeline to read it from, 0 if a lookup is required */ TimeLineID currTLI; @@ -250,16 +229,37 @@ struct XLogReaderState char *readRecordBuf; uint32 readRecordBufSize; + /* + * XLogReadRecord() state + */ + XLogReadRecordState readRecordState; /* state machine state */ + int recordGotLen; /* amount of current record that has already + * been read */ + int recordRemainLen; /* length of current record that remains */ + XLogRecPtr recordContRecPtr; /* where the current record continues */ + /* Buffer to hold error message */ char *errormsg_buf; }; +struct XLogFindNextRecordState +{ + XLogReaderState *reader_state; + XLogRecPtr targetRecPtr; + XLogRecPtr currRecPtr; +}; + +/* Report that data is available for decoding. */ +static inline void +XLogReaderSetInputData(XLogReaderState *state, int32 len) +{ + state->readLen = len; +} + /* Get a new XLogReader */ extern XLogReaderState *XLogReaderAllocate(int wal_segment_size, const char *waldir, - XLogReaderRoutine *routine, - void *private_data); -extern XLogReaderRoutine *LocalXLogReaderRoutine(void); + WALSegmentCleanupCB cleanup_cb); /* Free an XLogReader */ extern void XLogReaderFree(XLogReaderState *state); @@ -267,12 +267,14 @@ extern void XLogReaderFree(XLogReaderState *state); /* Position the XLogReader to given record */ extern void XLogBeginRead(XLogReaderState *state, XLogRecPtr RecPtr); #ifdef FRONTEND -extern XLogRecPtr XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr); +extern XLogFindNextRecordState *InitXLogFindNextRecord(XLogReaderState *reader_state, XLogRecPtr start_ptr); +extern bool XLogFindNextRecord(XLogFindNextRecordState *state); #endif /* FRONTEND */ /* Read the next XLog record. Returns NULL on end-of-WAL or failure */ -extern struct XLogRecord *XLogReadRecord(XLogReaderState *state, - char **errormsg); +extern XLogReadRecordResult XLogReadRecord(XLogReaderState *state, + XLogRecord **record, + char **errormsg); /* Validate a page */ extern bool XLogReaderValidatePageHeader(XLogReaderState *state, @@ -292,6 +294,7 @@ typedef struct WALReadError } WALReadError; extern bool WALRead(XLogReaderState *state, + WALSegmentOpenCB segopenfn, WALSegmentCloseCB sgclosefn, char *buf, XLogRecPtr startptr, Size count, TimeLineID tli, WALReadError *errinfo); |