@ -101,6 +101,7 @@ typedef enum XLogReadRecordResult
{
XLREAD_SUCCESS , /* record is successfully read */
XLREAD_NEED_DATA , /* need more data. see XLogReadRecord. */
XLREAD_FULL , /* cannot hold more data while reading ahead */
XLREAD_FAIL /* failed during reading a record */
} XLogReadRecordResult ;
@ -120,6 +121,30 @@ typedef enum XLogReadRecordState
XLREAD_CONTINUATION
} XLogReadRecordState ;
/*
* The decoded contents of a record . This occupies a contiguous region of
* memory , with main_data and blocks [ n ] . data pointing to memory after the
* members declared here .
*/
typedef struct DecodedXLogRecord
{
/* Private member used for resource management. */
size_t size ; /* total size of decoded record */
bool oversized ; /* outside the regular decode buffer? */
struct DecodedXLogRecord * next ; /* decoded record queue link */
/* Public members. */
XLogRecPtr lsn ; /* location */
XLogRecPtr next_lsn ; /* location of next record */
XLogRecord header ; /* header */
RepOriginId record_origin ;
TransactionId toplevel_xid ; /* XID of top-level transaction */
char * main_data ; /* record's main data portion */
uint32 main_data_len ; /* main data portion's length */
int max_block_id ; /* highest block_id in use (-1 if none) */
DecodedBkpBlock blocks [ FLEXIBLE_ARRAY_MEMBER ] ;
} DecodedXLogRecord ;
struct XLogReaderState
{
/*
@ -142,10 +167,12 @@ struct XLogReaderState
* 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 .
*
* Start and end point of last record returned by XLogReadRecord ( ) . These
* are also available as record - > lsn and record - > next_lsn .
*/
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
@ -170,27 +197,43 @@ struct XLogReaderState
* Use XLogRecGet * functions to investigate the record ; these fields
* should not be accessed directly .
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
* Start and end point of the last record read and decoded by
* XLogReadRecordInternal ( ) . NextRecPtr is also used as the position to
* decode next . Calling XLogBeginRead ( ) sets NextRecPtr and EndRecPtr to
* the requested starting position .
*/
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 ;
XLogRecPtr DecodeRecPtr ; /* start of last record decoded */
XLogRecPtr NextRecPtr ; /* end+1 of last record decoded */
XLogRecPtr PrevRecPtr ; /* start of previous record decoded */
TransactionId toplevel_xid ; /* XID of top-level transaction */
/* 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) */
/* Last record returned by XLogReadRecord(). */
DecodedXLogRecord * record ;
/* ----------------------------------------
* private / internal state
* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
*/
/*
* Buffer for decoded records . This is a circular buffer , though
* individual records can ' t be split in the middle , so some space is often
* wasted at the end . Oversized records that don ' t fit in this space are
* allocated separately .
*/
char * decode_buffer ;
size_t decode_buffer_size ;
bool free_decode_buffer ; /* need to free? */
char * decode_buffer_head ; /* write head */
char * decode_buffer_tail ; /* read head */
/*
* Queue of records that have been decoded . This is a linked list that
* usually consists of consecutive records in decode_buffer , but may also
* contain oversized records allocated with palloc ( ) .
*/
DecodedXLogRecord * decode_queue_head ; /* newest decoded record */
DecodedXLogRecord * decode_queue_tail ; /* oldest decoded record */
/* last read XLOG position for data currently in readBuf */
WALSegmentContext segcxt ;
WALOpenSegment seg ;
@ -230,7 +273,7 @@ struct XLogReaderState
uint32 readRecordBufSize ;
/*
* XLogReadRecord ( ) state
* XLogReadRecordInternal ( ) state
*/
XLogReadRecordState readRecordState ; /* state machine state */
int recordGotLen ; /* amount of current record that has already
@ -238,8 +281,11 @@ struct XLogReaderState
int recordRemainLen ; /* length of current record that remains */
XLogRecPtr recordContRecPtr ; /* where the current record continues */
DecodedXLogRecord * decoding ; /* record currently being decoded */
/* Buffer to hold error message */
char * errormsg_buf ;
bool errormsg_deferred ;
} ;
struct XLogFindNextRecordState
@ -264,6 +310,11 @@ extern XLogReaderState *XLogReaderAllocate(int wal_segment_size,
/* Free an XLogReader */
extern void XLogReaderFree ( XLogReaderState * state ) ;
/* Optionally provide a circular decoding buffer to allow readahead. */
extern void XLogReaderSetDecodeBuffer ( XLogReaderState * state ,
void * buffer ,
size_t size ) ;
/* Position the XLogReader to given record */
extern void XLogBeginRead ( XLogReaderState * state , XLogRecPtr RecPtr ) ;
# ifdef FRONTEND
@ -271,11 +322,21 @@ extern XLogFindNextRecordState *InitXLogFindNextRecord(XLogReaderState *reader_s
extern bool XLogFindNextRecord ( XLogFindNextRecordState * state ) ;
# endif /* FRONTEND */
/* Read the next XLog record. Returns NULL on end-of-WAL or failure */
/* Read the next record's header . Returns NULL on end-of-WAL or failure. */
extern XLogReadRecordResult XLogReadRecord ( XLogReaderState * state ,
XLogRecord * * record ,
char * * errormsg ) ;
/* Read the next decoded record. Returns NULL on end-of-WAL or failure. */
extern XLogReadRecordResult XLogNextRecord ( XLogReaderState * state ,
DecodedXLogRecord * * record ,
char * * errormsg ) ;
/* Try to read ahead, if there is space in the decoding buffer. */
extern XLogReadRecordResult XLogReadAhead ( XLogReaderState * state ,
DecodedXLogRecord * * record ,
char * * errormsg ) ;
/* Validate a page */
extern bool XLogReaderValidatePageHeader ( XLogReaderState * state ,
XLogRecPtr recptr , char * phdr ) ;
@ -300,25 +361,32 @@ extern bool WALRead(XLogReaderState *state,
/* Functions for decoding an XLogRecord */
extern bool DecodeXLogRecord ( XLogReaderState * state , XLogRecord * record ,
extern size_t DecodeXLogRecordRequiredSpace ( size_t xl_tot_len ) ;
extern bool DecodeXLogRecord ( XLogReaderState * state ,
DecodedXLogRecord * decoded ,
XLogRecord * record ,
XLogRecPtr lsn ,
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 XLogRecGetTopXid(decoder) ((decoder)->toplevel_xid)
# define XLogRecGetData(decoder) ((decoder)->main_data)
# define XLogRecGetDataLen(decoder) ((decoder)->main_data_len)
# define XLogRecHasAnyBlockRefs(decoder) ((decoder)->max_block_id >= 0)
# define XLogRecGetTotalLen(decoder) ((decoder)->record->header.xl_tot_len)
# define XLogRecGetPrev(decoder) ((decoder)->record->header.xl_prev)
# define XLogRecGetInfo(decoder) ((decoder)->record->header.xl_info)
# define XLogRecGetRmid(decoder) ((decoder)->record->header.xl_rmid)
# define XLogRecGetXid(decoder) ((decoder)->record->header.xl_xid)
# define XLogRecGetOrigin(decoder) ((decoder)->record->record_origin)
# define XLogRecGetTopXid(decoder) ((decoder)->record->toplevel_xid)
# define XLogRecGetData(decoder) ((decoder)->record->main_data)
# define XLogRecGetDataLen(decoder) ((decoder)->record->main_data_len)
# define XLogRecHasAnyBlockRefs(decoder) ((decoder)->record->max_block_id >= 0)
# define XLogRecMaxBlockId(decoder) ((decoder)->record->max_block_id)
# define XLogRecGetBlock(decoder, i) (&(decoder)->record->blocks[(i)])
# define XLogRecHasBlockRef(decoder, block_id) \
( ( decoder ) - > blocks [ block_id ] . in_use )
( ( decoder ) - > record - > max_block_id > = ( block_id ) ) & & \
( ( decoder ) - > record - > blocks [ block_id ] . in_use )
# define XLogRecHasBlockImage(decoder, block_id) \
( ( decoder ) - > blocks [ block_id ] . has_image )
( ( decoder ) - > record - > blocks [ block_id ] . has_image )
# define XLogRecBlockImageApply(decoder, block_id) \
( ( decoder ) - > blocks [ block_id ] . apply_image )
( ( decoder ) - > record - > blocks [ block_id ] . apply_image )
# ifndef FRONTEND
extern FullTransactionId XLogRecGetFullXid ( XLogReaderState * record ) ;
Thomas Munro
4 years ago