On Tuesday 22 December 2009 11:42:30 Simon Riggs wrote: > On Tue, 2009-12-22 at 03:19 +0100, Andres Freund wrote: > > On Monday 21 December 2009 16:48:52 Simon Riggs wrote: > > > Giving the drop database a snapshot is not the answer. I expect Andres > > > to be able to fix this with a simple patch that would not effect the > > > case of normal running. > > > > Actually its less simply than I had thought at first - I don't think the > > code ever handled that correctly. > > I might be wrong there, my knowledge of the involved code is a bit > > sparse... The whole conflict resolution builds on the concept of waiting > > for an VXid, but an idle backend does not have a valid vxid. Thats > > correct, right? > I don't see any mileage in making Startup process wait for an idle > session, so no real reason to wait for others either. So here is a small patch implementing that behaviour.
Andres
From 36f57e6f6b1d25d7433d9706682e53cc79b45a61 Mon Sep 17 00:00:00 2001 From: Andres Freund <and...@anarazel.de> Date: Sun, 27 Dec 2009 19:14:21 +0100 Subject: [PATCH] Fix the bug in HS that it is possible to stay connected to a database on a slave after it has been deleted. Instead immediately kill sessions using such a database - it is unlikely that those sessions will quit and its unlikely as well that its a significant issue to get thrown of a database which is dropped on the master. --- src/backend/commands/dbcommands.c | 22 ++++++++-------------- src/backend/storage/ipc/procarray.c | 25 +++++++++++++++++++++++++ src/include/storage/procarray.h | 1 + 3 files changed, 34 insertions(+), 14 deletions(-) diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c index 316222f..85d1d64 100644 --- a/src/backend/commands/dbcommands.c +++ b/src/backend/commands/dbcommands.c @@ -1945,22 +1945,16 @@ dbase_redo(XLogRecPtr lsn, XLogRecord *record) if (InHotStandby) { - VirtualTransactionId *database_users; - /* - * Find all users connected to this database and ask them - * politely to immediately kill their sessions before processing - * the drop database record, after the usual grace period. - * We don't wait for commit because drop database is - * non-transactional. + * We dont do the usual GetConflictingVirtualXIDs/ + * ResolveRecoveryConflictWithVirutalXIDs dance here because we are + * not only conflicting against concurrently running transactions + * but against concurrently running backends using this database. + * + * We do not wait for those sessions to exit by free will because + * quite likely that will never happen. So force them. */ - database_users = GetConflictingVirtualXIDs(InvalidTransactionId, - xlrec->db_id, - false); - - ResolveRecoveryConflictWithVirtualXIDs(database_users, - "drop database", - CONFLICT_MODE_FATAL); + CancelDBBackends(xlrec->db_id); } /* Drop pages for this database that are in the shared buffer cache */ diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index 8e2de35..07c7899 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -1827,6 +1827,31 @@ CountDBBackends(Oid databaseid) } /* + * CancelDBBackends --- cancel backends that are using specified database + */ +void +CancelDBBackends(Oid databaseid) +{ + ProcArrayStruct *arrayP = procArray; + int index; + + /* tell all backends to die */ + LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); + for (index = 0; index < arrayP->numProcs; index++) + { + volatile PGPROC *proc = arrayP->procs[index]; + + if (proc->databaseId == databaseid){ + if (proc->recoveryConflictMode < CONFLICT_MODE_FATAL){ + proc->recoveryConflictMode = CONFLICT_MODE_FATAL; + } + kill(proc->pid, SIGINT); + } + } + LWLockRelease(ProcArrayLock); +} + +/* * CountUserBackends --- count backends that are used by specified user */ int diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index 1cee639..707396b 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -63,6 +63,7 @@ extern pid_t CancelVirtualTransaction(VirtualTransactionId vxid, extern int CountActiveBackends(void); extern int CountDBBackends(Oid databaseid); +extern void CancelDBBackends(Oid databaseid); extern int CountUserBackends(Oid roleid); extern bool CountOtherDBBackends(Oid databaseId, int *nbackends, int *nprepared); -- 1.6.5.12.gd65df24
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