continuously, and requests vacuum runs of "autovacuum workers" to postmaster.
The workers do the actual vacuum work. This allows for future improvements,
like allowing multiple autovacuum jobs running in parallel.
For now, the code keeps the original behavior of having a single autovac
process at any time by sleeping until the previous worker has finished.
accessing it, like DROP DATABASE. This allows the regression tests to pass
with autovacuum enabled, which open the gates for finally enabling autovacuum
by default.
vacuums. This allows a OLTP-like system with big tables to continue
regular vacuuming on small-but-frequently-updated tables while the
big tables are being vacuumed.
Original patch from Hannu Krossing, rewritten by Tom Lane and updated
by me.
If a process abandons a wait in LockBufferForCleanup (in practice,
only happens if someone cancels a VACUUM) just before someone else
sends it a signal indicating the buffer is available, it was possible
for the wakeup to remain in the process' semaphore, causing misbehavior
next time the process waited for an lmgr lock. Rather than try to
prevent the race condition directly, it seems best to make the lock
manager robust against leftover wakeups, by having it repeat waiting
on the semaphore if the lock has not actually been granted or denied
yet.
an LWLock instead of a spinlock. This hardly matters on Unix machines
but should improve startup performance on Windows (or any port using
EXEC_BACKEND). Per previous discussion.
reduce contention for the former single LockMgrLock. Per my recent
proposal. I set it up for 16 partitions, but on a pgbench test this
gives only a marginal further improvement over 4 partitions --- we need
to test more scenarios to choose the number of partitions.
whether we seem to be running in a uniprocessor or multiprocessor.
The adjustment rules could probably still use further tweaking, but
I'm convinced this should be a win overall.
to 'Size' (that is, size_t), and install overflow detection checks in it.
This allows us to remove the former arbitrary restrictions on NBuffers
etc. It won't make any difference in a 32-bit machine, but in a 64-bit
machine you could theoretically have terabytes of shared buffers.
(How efficiently we could manage 'em remains to be seen.) Similarly,
num_temp_buffers, work_mem, and maintenance_work_mem can be set above
2Gb on a 64-bit machine. Original patch from Koichi Suzuki, additional
work by moi.
communication structure, and make it its own module with its own lock.
This should reduce contention at least a little, and it definitely makes
the code seem cleaner. Per my recent proposal.
Also performed an initial run through of upgrading our Copyright date to
extend to 2005 ... first run here was very simple ... change everything
where: grep 1996-2004 && the word 'Copyright' ... scanned through the
generated list with 'less' first, and after, to make sure that I only
picked up the right entries ...
PROCLOCK structs in shared memory now have only a bitmask for held
locks, rather than counts (making them 40 bytes smaller, which is a
good thing). Multiple locks within a transaction are counted in the
local hash table instead, and we have provision for tracking which
ResourceOwner each count belongs to. Solves recently reported problem
with memory leakage within long transactions.
number of active subtransaction XIDs in each backend's PGPROC entry,
and use this to avoid expensive probes into pg_subtrans during
TransactionIdIsInProgress. Extend EOXactCallback API to allow add-on
modules to get control at subxact start/end. (This is deliberately
not compatible with the former API, since any uses of that API probably
need manual review anyway.) Add basic reference documentation for
SAVEPOINT and related commands. Minor other cleanups to check off some
of the open issues for subtransactions.
Alvaro Herrera and Tom Lane.
keep track of portal-related resources separately from transaction-related
resources. This allows cursors to work in a somewhat sane fashion with
nested transactions. For now, cursor behavior is non-subtransactional,
that is a cursor's state does not roll back if you abort a subtransaction
that fetched from the cursor. We might want to change that later.
performance front, but with feature freeze upon us I think it's time to
drive a stake in the ground and say that this will be in 7.5.
Alvaro Herrera, with some help from Tom Lane.
method control structure, or a table of control structures.
. Use type LOCKMASK where an int is not a counter.
. Get rid of INVALID_TABLEID, use INVALID_LOCKMETHOD instead.
. Use INVALID_LOCKMETHOD instead of (LOCKMETHOD) NULL, because
LOCKMETHOD is not a pointer.
. Define and use macro LockMethodIsValid.
. Rename LOCKMETHOD to LOCKMETHODID.
. Remove global variable LongTermTableId in lmgr.c, because it is
never used.
. Make LockTableId static in lmgr.c, because it is used nowhere else.
Why not remove it and use DEFAULT_LOCKMETHOD?
. Rename the lock method control structure from LOCKMETHODTABLE to
LockMethodData. Introduce a pointer type named LockMethod.
. Remove elog(FATAL) after InitLockTable() call in
CreateSharedMemoryAndSemaphores(), because if something goes wrong,
there is elog(FATAL) in LockMethodTableInit(), and if this doesn't
help, an elog(ERROR) in InitLockTable() is promoted to FATAL.
. Make InitLockTable() void, because its only caller does not use its
return value any more.
. Rename variables in lock.c to avoid statements like
LockMethodTable[NumLockMethods] = lockMethodTable;
lockMethodTable = LockMethodTable[lockmethod];
. Change LOCKMETHODID type to uint16 to fit into struct LOCKTAG.
. Remove static variables BITS_OFF and BITS_ON from lock.c, because
I agree to this doubt:
* XXX is a fetch from a static array really faster than a shift?
. Define and use macros LOCKBIT_ON/OFF.
Manfred Koizar
This first part of the background writer does no syncing at all.
It's only purpose is to keep the LRU heads clean so that regular
backends seldom to never have to call write().
Jan
between signal handler and enable/disable code, avoid accumulation of
timing error due to trying to maintain remaining-time instead of
absolute-end-time, disable timeout before commit not after.
> Changes to avoid collisions with WIN32 & MFC names...
> 1. Renamed:
> a. PROC => PGPROC
> b. GetUserName() => GetUserNameFromId()
> c. GetCurrentTime() => GetCurrentDateTime()
> d. IGNORE => IGNORE_DTF in include/utils/datetime.h & utils/adt/datetim
>
> 2. Added _P to some lex/yacc tokens:
> CONST, CHAR, DELETE, FLOAT, GROUP, IN, OUT
Jan
As proof of concept, provide an alternate implementation based on POSIX
semaphores. Also push the SysV shared-memory implementation into a
separate file so that it can be replaced conveniently.
should be accounted for in the PROC_SEM_MAP_ENTRIES() macro. Otherwise
the ports that rely on this macro to size data structures are broken.
Mea culpa.
existing lock manager and spinlocks: it understands exclusive vs shared
lock but has few other fancy features. Replace most uses of spinlocks
with lightweight locks. All remaining uses of spinlocks have very short
lock hold times (a few dozen instructions), so tweak spinlock backoff
code to work efficiently given this assumption. All per my proposal on
pghackers 26-Sep-01.
a hung client or lost connection can't indefinitely block a postmaster
child (not to mention the possibility of deliberate DoS attacks).
Timeout is controlled by new authentication_timeout GUC variable,
which I set to 60 seconds by default ... does that seem reasonable?
for them, and making them just wastes time during backend startup/shutdown.
Also, remove compile-time MAXBACKENDS limit per long-ago proposal.
You can now set MaxBackends as high as your kernel can stand without
any reconfiguration/recompilation.
