index f592e71364dc010a1527f191e9157bb02b2bcf27..9f9ba5d308b3cb194cc9bd85b9716e0912b9dc71 100644 (file)
* far in the past.
*
* From this point on the VACUUM operation will do no further index
- * vacuuming or heap vacuuming. It will do any remaining pruning that
- * may be required, plus other heap-related and relation-level
- * maintenance tasks. But that's it.
+ * vacuuming or heap vacuuming. This VACUUM operation won't end up
+ * back here again.
*/
Assert(vacrel->do_failsafe);
}
@@ -2534,8 +2533,11 @@ lazy_check_needs_freeze(Buffer buf, bool *hastup, LVRelState *vacrel)
* relfrozenxid and/or relminmxid that is dangerously far in the past.
*
* Triggering the failsafe makes the ongoing VACUUM bypass any further index
- * vacuuming and heap vacuuming. It also stops the ongoing VACUUM from
- * applying any cost-based delay that may be in effect.
+ * vacuuming and heap vacuuming. Truncating the heap is also bypassed.
+ *
+ * Any remaining work (work that VACUUM cannot just bypass) is typically sped
+ * up when the failsafe triggers. VACUUM stops applying any cost-based delay
+ * that it started out with.
*
* Returns true when failsafe has been triggered.
*
@@ -3097,14 +3099,12 @@ lazy_cleanup_one_index(Relation indrel, IndexBulkDeleteResult *istat,
* Don't even think about it unless we have a shot at releasing a goodly
* number of pages. Otherwise, the time taken isn't worth it.
*
+ * Also don't attempt it if wraparound failsafe is in effect. It's hard to
+ * predict how long lazy_truncate_heap will take. Don't take any chances.
+ *
* Also don't attempt it if we are doing early pruning/vacuuming, because a
* scan which cannot find a truncated heap page cannot determine that the
- * snapshot is too old to read that page. We might be able to get away with
- * truncating all except one of the pages, setting its LSN to (at least) the
- * maximum of the truncated range if we also treated an index leaf tuple
- * pointing to a missing heap page as something to trigger the "snapshot too
- * old" error, but that seems fragile and seems like it deserves its own patch
- * if we consider it.
+ * snapshot is too old to read that page.
*
* This is split out so that we can test whether truncation is going to be
* called for before we actually do it. If you change the logic here, be
@@ -3118,6 +3118,9 @@ should_attempt_truncation(LVRelState *vacrel, VacuumParams *params)
if (params->truncate == VACOPT_TERNARY_DISABLED)
return false;
+ if (vacrel->do_failsafe)
+ return false;
+
possibly_freeable = vacrel->rel_pages - vacrel->nonempty_pages;
if (possibly_freeable > 0 &&
(possibly_freeable >= REL_TRUNCATE_MINIMUM ||