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| author | Noah Misch <noah@leadboat.com> | 2020-08-15 10:15:53 -0700 |
|---|---|---|
| committer | Noah Misch <noah@leadboat.com> | 2020-08-15 10:15:53 -0700 |
| commit | 566372b3d6435639e4cc4476d79b8505a0297c87 (patch) | |
| tree | cb23c4c35d85e463569d0759b275f484c240cc47 /src/backend/utils/adt/lockfuncs.c | |
| parent | d4d443b3bbbb3eb9cdc511564ef3c57fde7dd3ac (diff) | |
| download | postgresql-566372b3d6435639e4cc4476d79b8505a0297c87.tar.gz postgresql-566372b3d6435639e4cc4476d79b8505a0297c87.zip | |
Prevent concurrent SimpleLruTruncate() for any given SLRU.
The SimpleLruTruncate() header comment states the new coding rule. To
achieve this, add locktype "frozenid" and two LWLocks. This closes a
rare opportunity for data loss, which manifested as "apparent
wraparound" or "could not access status of transaction" errors. Data
loss is more likely in pg_multixact, due to released branches' thin
margin between multiStopLimit and multiWrapLimit. If a user's physical
replication primary logged ": apparent wraparound" messages, the user
should rebuild standbys of that primary regardless of symptoms. At less
risk is a cluster having emitted "not accepting commands" errors or
"must be vacuumed" warnings at some point. One can test a cluster for
this data loss by running VACUUM FREEZE in every database. Back-patch
to 9.5 (all supported versions).
Discussion: https://postgr.es/m/20190218073103.GA1434723@rfd.leadboat.com
Diffstat (limited to 'src/backend/utils/adt/lockfuncs.c')
| -rw-r--r-- | src/backend/utils/adt/lockfuncs.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/src/backend/utils/adt/lockfuncs.c b/src/backend/utils/adt/lockfuncs.c index e992d1bbfce..f592292d067 100644 --- a/src/backend/utils/adt/lockfuncs.c +++ b/src/backend/utils/adt/lockfuncs.c @@ -29,6 +29,7 @@ const char *const LockTagTypeNames[] = { "relation", "extend", + "frozenid", "page", "tuple", "transactionid", @@ -254,6 +255,17 @@ pg_lock_status(PG_FUNCTION_ARGS) nulls[8] = true; nulls[9] = true; break; + case LOCKTAG_DATABASE_FROZEN_IDS: + values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1); + nulls[2] = true; + nulls[3] = true; + nulls[4] = true; + nulls[5] = true; + nulls[6] = true; + nulls[7] = true; + nulls[8] = true; + nulls[9] = true; + break; case LOCKTAG_PAGE: values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1); values[2] = ObjectIdGetDatum(instance->locktag.locktag_field2); |