diff options
Diffstat (limited to 'src/backend/access/transam/xact.c')
| -rw-r--r-- | src/backend/access/transam/xact.c | 26 |
1 files changed, 18 insertions, 8 deletions
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index d8f6c658420..004f7e10e55 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -1369,14 +1369,24 @@ RecordTransactionCommit(void) /* * Transactions without an assigned xid can contain invalidation - * messages (e.g. explicit relcache invalidations or catcache - * invalidations for inplace updates); standbys need to process those. - * We can't emit a commit record without an xid, and we don't want to - * force assigning an xid, because that'd be problematic for e.g. - * vacuum. Hence we emit a bespoke record for the invalidations. We - * don't want to use that in case a commit record is emitted, so they - * happen synchronously with commits (besides not wanting to emit more - * WAL records). + * messages. While inplace updates do this, this is not known to be + * necessary; see comment at inplace CacheInvalidateHeapTuple(). + * Extensions might still rely on this capability, and standbys may + * need to process those invals. We can't emit a commit record + * without an xid, and we don't want to force assigning an xid, + * because that'd be problematic for e.g. vacuum. Hence we emit a + * bespoke record for the invalidations. We don't want to use that in + * case a commit record is emitted, so they happen synchronously with + * commits (besides not wanting to emit more WAL records). + * + * XXX Every known use of this capability is a defect. Since an XID + * isn't controlling visibility of the change that prompted invals, + * other sessions need the inval even if this transactions aborts. + * + * ON COMMIT DELETE ROWS does a nontransactional index_build(), which + * queues a relcache inval, including in transactions without an xid + * that had read the (empty) table. Standbys don't need any ON COMMIT + * DELETE ROWS invals, but we've not done the work to withhold them. */ if (nmsgs != 0) { |