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Diffstat (limited to 'src/backend/storage/lmgr/README')
| -rw-r--r-- | src/backend/storage/lmgr/README | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/src/backend/storage/lmgr/README b/src/backend/storage/lmgr/README index 8884676d284..5abef171169 100644 --- a/src/backend/storage/lmgr/README +++ b/src/backend/storage/lmgr/README @@ -1,4 +1,4 @@ -$PostgreSQL: pgsql/src/backend/storage/lmgr/README,v 1.21 2006/09/18 22:40:36 tgl Exp $ +$PostgreSQL: pgsql/src/backend/storage/lmgr/README,v 1.22 2007/10/26 20:45:10 alvherre Exp $ LOCKING OVERVIEW @@ -487,6 +487,13 @@ seems a safer approach than trying to allocate workspace on the fly; we don't want to risk having the deadlock detector run out of memory, else we really have no guarantees at all that deadlock will be detected. +6. We abuse the deadlock detector to implement autovacuum cancellation. +When we run the detector and we find that there's an autovacuum worker +involved in the waits-for graph, we store a pointer to its PGPROC, and +return a special return code (unless a hard deadlock has been detected). +The caller can then send a cancellation signal. This implements the +principle that autovacuum has a low locking priority (eg it must not block +DDL on the table). USER LOCKS |