diff options
Diffstat (limited to 'src/backend/storage')
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 48 |
1 files changed, 39 insertions, 9 deletions
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), |