diff options
Diffstat (limited to 'src/backend/access/transam/xlogreader.c')
| -rw-r--r-- | src/backend/access/transam/xlogreader.c | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c index e370fa984cd..456cdab461e 100644 --- a/src/backend/access/transam/xlogreader.c +++ b/src/backend/access/transam/xlogreader.c @@ -220,6 +220,7 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg) total_len; uint32 targetRecOff; uint32 pageHeaderSize; + bool assembled; bool gotheader; int readOff; @@ -235,6 +236,8 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg) state->errormsg_buf[0] = '\0'; ResetDecoder(state); + state->abortedRecPtr = InvalidXLogRecPtr; + state->missingContrecPtr = InvalidXLogRecPtr; if (RecPtr == InvalidXLogRecPtr) { @@ -263,7 +266,9 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg) randAccess = true; } +restart: state->currRecPtr = RecPtr; + assembled = false; targetPagePtr = RecPtr - (RecPtr % XLOG_BLCKSZ); targetRecOff = RecPtr % XLOG_BLCKSZ; @@ -373,6 +378,7 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg) char *buffer; uint32 gotlen; + assembled = true; /* Copy the first fragment of the record from the first page. */ memcpy(state->readRecordBuf, state->readBuf + RecPtr % XLOG_BLCKSZ, len); @@ -394,8 +400,25 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg) Assert(SizeOfXLogShortPHD <= readOff); - /* Check that the continuation on next page looks valid */ pageHeader = (XLogPageHeader) state->readBuf; + + /* + * If we were expecting a continuation record and got an + * "overwrite contrecord" flag, that means the continuation record + * was overwritten with a different record. Restart the read by + * assuming the address to read is the location where we found + * this flag; but keep track of the LSN of the record we were + * reading, for later verification. + */ + if (pageHeader->xlp_info & XLP_FIRST_IS_OVERWRITE_CONTRECORD) + { + state->overwrittenRecPtr = state->currRecPtr; + ResetDecoder(state); + RecPtr = targetPagePtr; + goto restart; + } + + /* Check that the continuation on next page looks valid */ if (!(pageHeader->xlp_info & XLP_FIRST_IS_CONTRECORD)) { report_invalid_record(state, @@ -497,6 +520,20 @@ XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg) return NULL; err: + if (assembled) + { + /* + * We get here when a record that spans multiple pages needs to be + * assembled, but something went wrong -- perhaps a contrecord piece + * was lost. If caller is WAL replay, it will know where the aborted + * record was and where to direct followup WAL to be written, marking + * the next piece with XLP_FIRST_IS_OVERWRITE_CONTRECORD, which will + * in turn signal downstream WAL consumers that the broken WAL record + * is to be ignored. + */ + state->abortedRecPtr = RecPtr; + state->missingContrecPtr = targetPagePtr; + } /* * Invalidate the read state. We might read from a different source after |