99 lines
3.0 KiB
Plaintext
99 lines
3.0 KiB
Plaintext
$PostgreSQL: pgsql/contrib/pgrowlocks/README.pgrowlocks,v 1.1 2006/04/23 01:12:58 ishii Exp $
|
|
|
|
pgrowlocks README Tatsuo Ishii
|
|
|
|
1. What is pgrowlocks?
|
|
|
|
pgrowlocks shows row locking information for specified table.
|
|
|
|
pgrowlocks returns following data type:
|
|
|
|
CREATE TYPE pgrowlocks_type AS (
|
|
locked_row TID, -- row TID
|
|
lock_type TEXT, -- lock type
|
|
locker XID, -- locking XID
|
|
multi bool, -- multi XID?
|
|
xids xid[], -- multi XIDs
|
|
pids INTEGER[] -- locker's process id
|
|
);
|
|
|
|
Here is a sample execution of pgrowlocks:
|
|
|
|
test=# SELECT * FROM pgrowlocks('t1');
|
|
locked_row | lock_type | locker | multi | xids | pids
|
|
------------+-----------+--------+-------+-----------+---------------
|
|
(0,1) | Shared | 19 | t | {804,805} | {29066,29068}
|
|
(0,2) | Shared | 19 | t | {804,805} | {29066,29068}
|
|
(0,3) | Exclusive | 804 | f | {804} | {29066}
|
|
(0,4) | Exclusive | 804 | f | {804} | {29066}
|
|
(4 rows)
|
|
|
|
locked_row -- tuple ID(TID) of each locked rows
|
|
lock_type -- "Shared" for shared lock, "Exclusive" for exclusive lock
|
|
locker -- transaction ID of locker (note 1)
|
|
multi -- "t" if locker is a multi transaction, otherwise "f"
|
|
xids -- XIDs of lockers (note 2)
|
|
pids -- process ids of locking backends
|
|
|
|
note1: if the locker is multi transaction, it represents the multi ID
|
|
|
|
note2: if the locker is multi, multiple data are shown
|
|
|
|
2. Installing pgrowlocks
|
|
|
|
Installing pgrowlocks requires PostgreSQL 8.0 or later source tree.
|
|
|
|
$ cd /usr/local/src/postgresql-8.1/contrib
|
|
$ tar xfz /tmp/pgrowlocks-1.0.tar.gz
|
|
|
|
If you are using PostgreSQL 8.0, you need to modify pgrowlocks source code.
|
|
Around line 61, you will see:
|
|
|
|
#undef MAKERANGEVARFROMNAMELIST_HAS_TWO_ARGS
|
|
|
|
change this to:
|
|
|
|
#define MAKERANGEVARFROMNAMELIST_HAS_TWO_ARGS
|
|
|
|
$ make
|
|
$ make install
|
|
|
|
$ psql -e -f pgrowlocks.sql test
|
|
|
|
3. How to use pgrowlocks
|
|
|
|
The calling sequence for pgrowlocks is as follows:
|
|
|
|
CREATE OR REPLACE FUNCTION pgrowlocks(text) RETURNS pgrowlocks_type
|
|
AS 'MODULE_PATHNAME', 'pgrowlocks'
|
|
LANGUAGE 'c' WITH (isstrict);
|
|
|
|
The parameter is a name of table. pgrowlocks returns type pgrowlocks_type.
|
|
|
|
pgrowlocks grab AccessShareLock for the target table and read each
|
|
row one by one to get the row locking information. You should
|
|
notice that:
|
|
|
|
1) if the table is exclusive locked by someone else, pgrowlocks
|
|
will be blocked.
|
|
|
|
2) pgrowlocks may show incorrect information if there's a new
|
|
lock or a lock is freeed while its execution.
|
|
|
|
pgrowlocks does not show the contents of locked rows. If you want
|
|
to take a look at the row contents at the same time, you could do
|
|
something like this:
|
|
|
|
SELECT * FROM accounts AS a, pgrowlocks('accounts') AS p WHERE p.locked_ row = a.ctid;
|
|
|
|
|
|
4. License
|
|
|
|
pgrowlocks is distribute under (modified) BSD license described in
|
|
the source file.
|
|
|
|
5. History
|
|
|
|
2006/03/21 pgrowlocks version 1.1 released (tested on 8.2 current)
|
|
2005/08/22 pgrowlocks version 1.0 released
|