diff options
| author | Noah Misch <noah@leadboat.com> | 2020-08-15 10:15:53 -0700 |
|---|---|---|
| committer | Noah Misch <noah@leadboat.com> | 2020-08-15 10:15:56 -0700 |
| commit | 30e68a2abb3890c3292ff0b2422a7ea04d62acdd (patch) | |
| tree | f4abe39532c9db31c78114d94d6b08584e551e16 /src/include | |
| parent | 912fb290c5dd087ccc4b04c19692137bb786a9fd (diff) | |
| download | postgresql-30e68a2abb3890c3292ff0b2422a7ea04d62acdd.tar.gz postgresql-30e68a2abb3890c3292ff0b2422a7ea04d62acdd.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/include')
| -rw-r--r-- | src/include/storage/lmgr.h | 3 | ||||
| -rw-r--r-- | src/include/storage/lock.h | 10 |
2 files changed, 13 insertions, 0 deletions
diff --git a/src/include/storage/lmgr.h b/src/include/storage/lmgr.h index 099e18f2b75..3f42000bda8 100644 --- a/src/include/storage/lmgr.h +++ b/src/include/storage/lmgr.h @@ -59,6 +59,9 @@ extern bool ConditionalLockRelationForExtension(Relation relation, LOCKMODE lockmode); extern int RelationExtensionLockWaiterCount(Relation relation); +/* Lock to recompute pg_database.datfrozenxid in the current database */ +extern void LockDatabaseFrozenIds(LOCKMODE lockmode); + /* Lock a page (currently only used within indexes) */ extern void LockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode); extern bool ConditionalLockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode); diff --git a/src/include/storage/lock.h b/src/include/storage/lock.h index 986bb6433a0..5dc7f873680 100644 --- a/src/include/storage/lock.h +++ b/src/include/storage/lock.h @@ -139,6 +139,7 @@ typedef enum LockTagType { LOCKTAG_RELATION, /* whole relation */ LOCKTAG_RELATION_EXTEND, /* the right to extend a relation */ + LOCKTAG_DATABASE_FROZEN_IDS, /* pg_database.datfrozenxid */ LOCKTAG_PAGE, /* one page of a relation */ LOCKTAG_TUPLE, /* one physical tuple */ LOCKTAG_TRANSACTION, /* transaction (for waiting for xact done) */ @@ -195,6 +196,15 @@ typedef struct LOCKTAG (locktag).locktag_type = LOCKTAG_RELATION_EXTEND, \ (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD) +/* ID info for frozen IDs is DB OID */ +#define SET_LOCKTAG_DATABASE_FROZEN_IDS(locktag,dboid) \ + ((locktag).locktag_field1 = (dboid), \ + (locktag).locktag_field2 = 0, \ + (locktag).locktag_field3 = 0, \ + (locktag).locktag_field4 = 0, \ + (locktag).locktag_type = LOCKTAG_DATABASE_FROZEN_IDS, \ + (locktag).locktag_lockmethodid = DEFAULT_LOCKMETHOD) + /* ID info for a page is RELATION info + BlockNumber */ #define SET_LOCKTAG_PAGE(locktag,dboid,reloid,blocknum) \ ((locktag).locktag_field1 = (dboid), \ |