Commit Graph

20 Commits

Author SHA1 Message Date
Tom Lane
c599a247bb Simplify lock manager data structures by making a clear separation between
the data defining the semantics of a lock method (ie, conflict resolution
table and ancillary data, which is all constant) and the hash tables
storing the current state.  The only thing we give up by this is the
ability to use separate hashtables for different lock methods, but there
is no need for that anyway.  Put some extra fields into the LockMethod
definition structs to clean up some other uglinesses, like hard-wired
tests for DEFAULT_LOCKMETHOD and USER_LOCKMETHOD.  This commit doesn't
do anything about the performance issues we were discussing, but it clears
away some of the underbrush that's in the way of fixing that.
2005-12-09 01:22:04 +00:00
Tom Lane
8563ccae2c Simplify shared-memory lock data structures as per recent discussion:
it is sufficient to track whether a backend holds a lock or not, and
store information about transaction vs. session locks only in the
inside-the-backend LocalLockTable.  Since there can now be but one
PROCLOCK per lock per backend, LockCountMyLocks() is no longer needed,
thus eliminating some O(N^2) behavior when a backend holds many locks.
Also simplify the LockAcquire/LockRelease API by passing just a
'sessionLock' boolean instead of a transaction ID.  The previous API
was designed with the idea that per-transaction lock holding would be
important for subtransactions, but now that we have subtransactions we
know that this is unwanted.  While at it, add an 'isTempObject' parameter
to LockAcquire to indicate whether the lock is being taken on a temp
table.  This is not used just yet, but will be needed shortly for
two-phase commit.
2005-06-14 22:15:33 +00:00
Tom Lane
140b078d2a Improve LockAcquire API per my recent proposal. All error conditions
are now reported via elog, eliminating the need to test the result code
at most call sites.  Make it possible for the caller to distinguish a
freshly acquired lock from one already held in the current transaction.
Use that capability to avoid redundant AcceptInvalidationMessages() calls
in LockRelation().
2005-05-29 22:45:02 +00:00
Tom Lane
191b13aaca Factor out lock cleanup code that is needed in several places in lock.c.
Also, remove the rather useless return value of LockReleaseAll.  Change
response to detection of corruption in the shared lock tables to PANIC,
since that is the only way of cleaning up fully.
Originally an idea of Heikki Linnakangas, variously hacked on by
Alvaro Herrera and Tom Lane.
2005-05-19 23:30:18 +00:00
Tom Lane
a9c4c9cd52 Extend the pg_locks system view so that it can fully display all lock
types, as per recent discussion.
2005-05-17 21:46:11 +00:00
Tom Lane
3a694bb0a1 Restructure LOCKTAG as per discussions of a couple months ago.
Essentially, we shoehorn in a lockable-object-type field by taking
a byte away from the lockmethodid, which can surely fit in one byte
instead of two.  This allows less artificial definitions of all the
other fields of LOCKTAG; we can get rid of the special pg_xactlock
pseudo-relation, and also support locks on individual tuples and
general database objects (including shared objects).  None of those
possibilities are actually exploited just yet, however.

I removed pg_xactlock from pg_class, but did not force initdb for
that change.  At this point, relkind 's' (SPECIAL) is unused and
could be removed entirely.
2005-04-29 22:28:24 +00:00
Tom Lane
1785acebf2 Introduce local hash table for lock state, as per recent proposal.
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.
2004-08-27 17:07:42 +00:00
Tom Lane
fe548629c5 Invent ResourceOwner mechanism as per my recent proposal, and use it to
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.
2004-07-17 03:32:14 +00:00
Tom Lane
573a71a5da Nested transactions. There is still much left to do, especially on the
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.
2004-07-01 00:52:04 +00:00
Tom Lane
863aceb54f Get rid of PID entries in shmem hash table; there is no longer any need
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.
2001-09-07 00:27:30 +00:00
Tom Lane
d8d9ed931e Add support to lock manager for conditionally locking a lock (ie,
return without waiting if we can't get the lock immediately).
Not used yet, but will be needed for concurrent VACUUM.
2001-06-22 00:04:59 +00:00
Tom Lane
6cc842abd3 Revise lock manager to support "session level" locks as well as "transaction
level" locks.  A session lock is not released at transaction commit (but it
is released on transaction abort, to ensure recovery after an elog(ERROR)).
In VACUUM, use a session lock to protect the master table while vacuuming a
TOAST table, so that the TOAST table can be done in an independent
transaction.

I also took this opportunity to do some cleanup and renaming in the lock
code.  The previously noted bug in ProcLockWakeup, that it couldn't wake up
any waiters beyond the first non-wakeable waiter, is now fixed.  Also found
a previously unknown bug of the same kind (failure to scan all members of
a lock queue in some cases) in DeadLockCheck.  This might have led to failure
to detect a deadlock condition, resulting in indefinite waits, but it's
difficult to characterize the conditions required to trigger a failure.
2000-12-22 00:51:54 +00:00
Bruce Momjian
52f77df613 Ye-old pgindent run. Same 4-space tabs. 2000-04-12 17:17:23 +00:00
Bruce Momjian
5a017b96ad Apply contrib patch from Massimo 1999-09-27 20:04:14 +00:00
Bruce Momjian
27b8143944 Hi,
I have updated my contrib code for version 6.5. In the attachment you will
find the directories array, datetime, miscutil, string, tools and userlocks
which replace the corresponding directories under contrib.

In contrib/tools you will find some developement scripts which I use while
hacking the sources. I hope they will be useful for some other people.

I have also added a contrib/Makefile which tries to compile and install all
the contribs. Unfortunately many of them don't have a Makefile or don't
compile cleanly.

--
Massimo Dal Zotto
1999-06-05 19:09:48 +00:00
Vadim B. Mikheev
bbf37e9477 typedef struct LTAG
{
    Oid             relId;
    Oid             dbId;
    union
    {
        BlockNumber     blkno;
        TransactionId   xid;
    }               objId;
>
> Added:
>    /*
>     * offnum should be part of objId.tupleId above, but would increase
>     * sizeof(LOCKTAG) and so moved here; currently used by userlocks only.
>     */
>    OffsetNumber    offnum;
    uint16          lockmethod;     /* needed by userlocks */
} LOCKTAG;

gmake clean required...
User locks are ready for 6.5 release...
1999-06-01 09:35:39 +00:00
Bruce Momjian
07842084fe pgindent run over code. 1999-05-25 16:15:34 +00:00
Marc G. Fournier
eec4c7366f From: Massimo Dal Zotto <dz@cs.unitn.it>
Here is a tar file the new directories, which substitute the old ones
in contrib. Please remove the old directories array, datetime, miscutil,
string and userlock before unpacking the tar file in contrib.

Note that as the modules are now installed in lib/modules I install all
my sql code in lib/sql. In my opinion also the other contributors should
follow these rules.
1998-08-30 19:37:51 +00:00
Bruce Momjian
a32450a585 pgindent run before 6.3 release, with Thomas' requested changes. 1998-02-26 04:46:47 +00:00
Bruce Momjian
951986c550 Update of contrib stuff from massimo. 1997-11-05 21:38:25 +00:00