diff options
Diffstat (limited to 'src/backend/access/heap/heapam.c')
| -rw-r--r-- | src/backend/access/heap/heapam.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index ed2e3021799..c1a4de14a59 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -6507,9 +6507,17 @@ heap_inplace_update_and_unlock(Relation relation, * [crash] * [recovery restores datfrozenxid w/o relfrozenxid] * - * Like in MarkBufferDirtyHint() subroutine XLogSaveBufferForHint(), copy - * the buffer to the stack before logging. Here, that facilitates a FPI - * of the post-mutation block before we accept other sessions seeing it. + * Mimic MarkBufferDirtyHint() subroutine XLogSaveBufferForHint(). + * Specifically, use DELAY_CHKPT_START, and copy the buffer to the stack. + * The stack copy facilitates a FPI of the post-mutation block before we + * accept other sessions seeing it. DELAY_CHKPT_START allows us to + * XLogInsert() before MarkBufferDirty(). Since XLogSaveBufferForHint() + * can operate under BUFFER_LOCK_SHARED, it can't avoid DELAY_CHKPT_START. + * This function, however, likely could avoid it with the following order + * of operations: MarkBufferDirty(), XLogInsert(), memcpy(). Opt to use + * DELAY_CHKPT_START here, too, as a way to have fewer distinct code + * patterns to analyze. Inplace update isn't so frequent that it should + * pursue the small optimization of skipping DELAY_CHKPT_START. */ Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0); START_CRIT_SECTION(); |