diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 29 | ||||
| -rw-r--r-- | src/backend/utils/time/tqual.c | 12 | ||||
| -rw-r--r-- | src/include/storage/bufmgr.h | 2 |
3 files changed, 38 insertions, 5 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index 8647eddcb42..f47f1b66b1f 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -1929,6 +1929,35 @@ RelationGetNumberOfBlocksInFork(Relation relation, ForkNumber forkNum) return smgrnblocks(relation->rd_smgr, forkNum); } +/* + * BufferIsPermanent + * Determines whether a buffer will potentially still be around after + * a crash. Caller must hold a buffer pin. + */ +bool +BufferIsPermanent(Buffer buffer) +{ + volatile BufferDesc *bufHdr; + + /* Local buffers are used only for temp relations. */ + if (BufferIsLocal(buffer)) + return false; + + /* Make sure we've got a real buffer, and that we hold a pin on it. */ + Assert(BufferIsValid(buffer)); + Assert(BufferIsPinned(buffer)); + + /* + * BM_PERMANENT can't be changed while we hold a pin on the buffer, so + * we need not bother with the buffer header spinlock. Even if someone + * else changes the buffer header flags while we're doing this, we assume + * that changing an aligned 2-byte BufFlags value is atomic, so we'll read + * the old value or the new value, but not random garbage. + */ + bufHdr = &BufferDescriptors[buffer - 1]; + return (bufHdr->flags & BM_PERMANENT) != 0; +} + /* --------------------------------------------------------------------- * DropRelFileNodeBuffers * diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c index d81ee7de062..1c4b74d94b5 100644 --- a/src/backend/utils/time/tqual.c +++ b/src/backend/utils/time/tqual.c @@ -82,10 +82,12 @@ static bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot); * Set commit/abort hint bits on a tuple, if appropriate at this time. * * It is only safe to set a transaction-committed hint bit if we know the - * transaction's commit record has been flushed to disk. We cannot change - * the LSN of the page here because we may hold only a share lock on the - * buffer, so we can't use the LSN to interlock this; we have to just refrain - * from setting the hint bit until some future re-examination of the tuple. + * transaction's commit record has been flushed to disk, or if the table is + * temporary or unlogged and will be obliterated by a crash anyway. We + * cannot change the LSN of the page here because we may hold only a share + * lock on the buffer, so we can't use the LSN to interlock this; we have to + * just refrain from setting the hint bit until some future re-examination + * of the tuple. * * We can always set hint bits when marking a transaction aborted. (Some * code in heapam.c relies on that!) @@ -113,7 +115,7 @@ SetHintBits(HeapTupleHeader tuple, Buffer buffer, /* NB: xid must be known committed here! */ XLogRecPtr commitLSN = TransactionIdGetCommitLSN(xid); - if (XLogNeedsFlush(commitLSN)) + if (XLogNeedsFlush(commitLSN) && BufferIsPermanent(buffer)) return; /* not flushed yet, so don't set hint */ } diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 82b43006f3e..49b5d314ff0 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -192,6 +192,8 @@ extern void DropDatabaseBuffers(Oid dbid); #define RelationGetNumberOfBlocks(reln) \ RelationGetNumberOfBlocksInFork(reln, MAIN_FORKNUM) +extern bool BufferIsPermanent(Buffer buffer); + #ifdef NOT_USED extern void PrintPinnedBufs(void); #endif |