diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/transam/xlogutils.c | 11 | ||||
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 48 | ||||
| -rw-r--r-- | src/include/storage/bufmgr.h | 3 |
3 files changed, 49 insertions, 13 deletions
diff --git a/src/backend/access/transam/xlogutils.c b/src/backend/access/transam/xlogutils.c index a433ad9fca7..39c3269bc11 100644 --- a/src/backend/access/transam/xlogutils.c +++ b/src/backend/access/transam/xlogutils.c @@ -11,7 +11,7 @@ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/backend/access/transam/xlogutils.c,v 1.49 2007/01/05 22:19:24 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/xlogutils.c,v 1.50 2007/05/02 23:18:03 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -206,7 +206,9 @@ XLogCheckInvalidPages(void) * If "init" is true then the caller intends to rewrite the page fully * using the info in the XLOG record. In this case we will extend the * relation if needed to make the page exist, and we will not complain about - * the page being "new" (all zeroes). + * the page being "new" (all zeroes); in fact, we usually will supply a + * zeroed buffer without reading the page at all, so as to avoid unnecessary + * failure if the page is present on disk but has corrupt headers. * * If "init" is false then the caller needs the page to be valid already. * If the page doesn't exist or contains zeroes, we return InvalidBuffer. @@ -226,7 +228,10 @@ XLogReadBuffer(Relation reln, BlockNumber blkno, bool init) if (blkno < lastblock) { /* page exists in file */ - buffer = ReadBuffer(reln, blkno); + if (init) + buffer = ReadOrZeroBuffer(reln, blkno); + else + buffer = ReadBuffer(reln, blkno); } else { diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 8ce7700c9cb..c3d16a9418f 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.216 2007/03/30 18:34:55 mha Exp $ + * $PostgreSQL: pgsql/src/backend/storage/buffer/bufmgr.c,v 1.217 2007/05/02 23:18:03 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -17,6 +17,12 @@ * and pin it so that no one can destroy it while this process * is using it. * + * ReadOrZeroBuffer() -- like ReadBuffer, but if the page is not already in + * cache we don't read it, but just return a zeroed-out buffer. Useful + * when the caller intends to fill the page from scratch, since this + * saves I/O and avoids unnecessary failure if the page-on-disk has + * corrupt page headers. + * * ReleaseBuffer() -- unpin a buffer * * MarkBufferDirty() -- mark a pinned buffer's contents as "dirty". @@ -87,6 +93,8 @@ static volatile BufferDesc *PinCountWaitBuf = NULL; extern PgStat_MsgBgWriter BgWriterStats; +static Buffer ReadBuffer_common(Relation reln, BlockNumber blockNum, + bool zeroPage); static bool PinBuffer(volatile BufferDesc *buf); static void PinBuffer_Locked(volatile BufferDesc *buf); static void UnpinBuffer(volatile BufferDesc *buf, @@ -121,6 +129,27 @@ static void AtProcExit_Buffers(int code, Datum arg); Buffer ReadBuffer(Relation reln, BlockNumber blockNum) { + return ReadBuffer_common(reln, blockNum, false); +} + +/* + * ReadOrZeroBuffer -- like ReadBuffer, but if the page isn't in buffer + * cache already, it's filled with zeros instead of reading it from + * disk. The caller is expected to overwrite the whole buffer, + * so that the current page contents are not interesting. + */ +Buffer +ReadOrZeroBuffer(Relation reln, BlockNumber blockNum) +{ + return ReadBuffer_common(reln, blockNum, true); +} + +/* + * ReadBuffer_common -- common logic for ReadBuffer and ReadOrZeroBuffer + */ +static Buffer +ReadBuffer_common(Relation reln, BlockNumber blockNum, bool zeroPage) +{ volatile BufferDesc *bufHdr; Block bufBlock; bool found; @@ -253,17 +282,18 @@ ReadBuffer(Relation reln, BlockNumber blockNum) } else { - smgrread(reln->rd_smgr, blockNum, (char *) bufBlock); + /* + * Read in the page, unless the caller intends to overwrite it + * and just wants us to allocate a buffer. + */ + if (zeroPage) + MemSet((char *) bufBlock, 0, BLCKSZ); + else + smgrread(reln->rd_smgr, blockNum, (char *) bufBlock); /* check for garbage data */ if (!PageHeaderIsValid((PageHeader) bufBlock)) { - /* - * During WAL recovery, the first access to any data page should - * overwrite the whole page from the WAL; so a clobbered page - * header is not reason to fail. Hence, when InRecovery we may - * always act as though zero_damaged_pages is ON. - */ - if (zero_damaged_pages || InRecovery) + if (zero_damaged_pages) { ereport(WARNING, (errcode(ERRCODE_DATA_CORRUPTED), diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 80ad4ae6964..ad203621793 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.102 2007/01/05 22:19:57 momjian Exp $ + * $PostgreSQL: pgsql/src/include/storage/bufmgr.h,v 1.103 2007/05/02 23:18:03 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -111,6 +111,7 @@ extern DLLIMPORT int32 *LocalRefCount; * prototypes for functions in bufmgr.c */ extern Buffer ReadBuffer(Relation reln, BlockNumber blockNum); +extern Buffer ReadOrZeroBuffer(Relation reln, BlockNumber blockNum); extern void ReleaseBuffer(Buffer buffer); extern void UnlockReleaseBuffer(Buffer buffer); extern void MarkBufferDirty(Buffer buffer); |