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Add new contrib function pgrowlocks. See README.pgrowlocks for more details.

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Tatsuo Ishii 2006-04-23 01:12:58 +00:00
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commit 66126f9687
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#-------------------------------------------------------------------------
#
# pgrowlocks Makefile
#
# $PostgreSQL: pgsql/contrib/pgrowlocks/Makefile,v 1.1 2006/04/23 01:12:58 ishii Exp $
#
#-------------------------------------------------------------------------
SRCS = pgrowlocks.c
MODULE_big = pgrowlocks
OBJS = $(SRCS:.c=.o)
DOCS = README.pgrowlocks README.pgrowlocks.euc_jp
DATA_built = pgrowlocks.sql
ifdef USE_PGXS
PGXS = $(shell pg_config --pgxs)
include $(PGXS)
else
subdir = contrib/pgrowlocks
top_builddir = ../..
include $(top_builddir)/src/Makefile.global
include $(top_srcdir)/contrib/contrib-global.mk
endif

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$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

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$PostgreSQL: pgsql/contrib/pgrowlocks/README.pgrowlocks.euc_jp,v 1.1 2006/04/23 01:12:58 ishii Exp $
pgrowlocks README 石井達夫
1. pgrowlocksとは
pgrowlocksは，指定されたテーブルの行ロックに関する情報を表示します．
pgrowlocksの返す型は，以下のようになります．
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
);
実行例を示します．
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)
各項目の説明です．
locked_row -- ロックされた行のタプルID(TID)
lock_type -- 共有ロックなら"Shared"，排他ロックなら"Exclusive"
locker -- ロックをかけているトランザクションID[注1]
multi -- lockerがマルチトランザクションならtそうでなければf
xids -- ロックをかけているトランザクションID[注2]
pids -- ロックをかけているバックエンドプロセスのプロセスID[注2]
[注1: lockerがマルチなら，トランザクションIDではなくてマルチIDになり
ます．]
[注2: lockerがマルチの場合，複数のデータが表示されます．]
2. pgrowlocksのインストール
pgrowlocksのインストールには，PostgreSQLをインストールしたときのソー
スツリーが必要です．今のところ対応しているバージョンはPostgreSQL
8.0以降です．
ここではPostgreSQLのソースは/usr/local/src/postgresql-8.1/に展開さ
れているものとします．
1) pgrowlocksのソースを展開します．ソースファイルは
/tmp/pgrowlocks-1.0.tar.gzに置いてあるものとします．
$ cd /usr/local/src/postgresql-8.1/contrib
$ tar xfz pgrowlocks-1.0.tar.gz
2) PostgreSQL 8.0の場合は，ソースの一部に修正が必要です．
pgrowlocks.cの61行目辺りに
#undef MAKERANGEVARFROMNAMELIST_HAS_TWO_ARGS
というのがあるので，これを
#define MAKERANGEVARFROMNAMELIST_HAS_TWO_ARGS
に書き換えます(undef->defineにします)．
3) コンパイルして関数の共有ライブラリをインストールします．
$ make
$ make install
4) ユーザ定義関数を登録します．
$ psql -e -f /usr/local/pgsql/share/contrib/pgrowlocks.sql test
この例では"test"というデータベースに登録していますが，もし他のデー
タベースに登録する場合はここを読み替えてください．
3. pgrowlocksの使い方
pgrowlocksの呼び出し形式は以下です．
CREATE OR REPLACE FUNCTION pgrowlocks(text) RETURNS pgrowlocks_type
AS 'MODULE_PATHNAME', 'pgrowlocks'
LANGUAGE 'c' WITH (isstrict);
第一引数: テーブル名
関数の戻りはpgrowlocks_type型です．
pgrowlocksはテーブルにAccessShareLockロックをかけ，1行ずつ読み出し
ては行ロックがかかっているかどうかチェックします．以下の点に注意し
てください．
1) 該当テーブルに排他ロックがかかっていると，pgrowlocksの実行はブロッ
クされます．
2) pgrowlocksの実行中に新たにかかったり，解除された行ロックに関する
情報はpgrowlocksの実行結果に反映されていない可能性があります．
pgrowlocksはロックされた行の内容は表示しません．行内容を見たい場合
は，テーブルをpgrowlocksのlocked_rows列で結合します．例を示します．
SELECT * FROM accounts AS a, pgrowlocks('accounts') AS p WHERE p.locked_ row = a.ctid;
4. pgrowlocksのライセンス条件について
pgrowlocks.cの冒頭に書いてある通りです(修正BSDライセンスに準じてい
ます)．また，pgrowlocks は完全に無保証です．pgrowlocks を使用したこ
とによって生じるいかなる結果に関しても責任を負いません．
5. 改訂履歴
2006/03/21 pgrowlocks バージョン 1.1リリース(8.2 currentでテスト)
2005/08/22 pgrowlocks バージョン 1.0リリース

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/*
* $PostgreSQL: pgsql/contrib/pgrowlocks/pgrowlocks.c,v 1.1 2006/04/23 01:12:58 ishii Exp $
*
* Copyright (c) 2005-2006 Tatsuo Ishii
*
* Permission to use, copy, modify, and distribute this software and
* its documentation for any purpose, without fee, and without a
* written agreement is hereby granted, provided that the above
* copyright notice and this paragraph and the following two
* paragraphs appear in all copies.
*
* IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
* INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
* DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
* THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
* IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
* SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*/
#include "postgres.h"
#include "funcapi.h"
#include "access/heapam.h"
#include "access/transam.h"
#include "catalog/namespace.h"
#include "catalog/pg_type.h"
#include "storage/proc.h"
#include "utils/builtins.h"
#ifdef HEAP_XMAX_SHARED_LOCK
#include "access/multixact.h"
#include "storage/procarray.h"
#endif
PG_FUNCTION_INFO_V1(pgrowlocks);
extern Datum pgrowlocks(PG_FUNCTION_ARGS);
/* ----------
* pgrowlocks:
* returns tids of rows being locked
*
* C FUNCTION definition
* pgrowlocks(text) returns set of pgrowlocks_type
* see pgrowlocks.sql for pgrowlocks_type
* ----------
*/
#define DUMMY_TUPLE "public.pgrowlocks_type"
#define NCHARS 32
/*
* define this if makeRangeVarFromNameList() has two arguments. As far
* as I know, this only happens in 8.0.x.
*/
#undef MAKERANGEVARFROMNAMELIST_HAS_TWO_ARGS
typedef struct {
HeapScanDesc scan;
int ncolumns;
} MyData;
Datum
pgrowlocks(PG_FUNCTION_ARGS)
{
FuncCallContext *funcctx;
HeapScanDesc scan;
HeapTuple tuple;
TupleDesc tupdesc;
AttInMetadata *attinmeta;
Datum result;
MyData *mydata;
Relation rel;
if (SRF_IS_FIRSTCALL())
{
text *relname;
RangeVar *relrv;
MemoryContext oldcontext;
funcctx = SRF_FIRSTCALL_INIT();
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
tupdesc = RelationNameGetTupleDesc(DUMMY_TUPLE);
attinmeta = TupleDescGetAttInMetadata(tupdesc);
funcctx->attinmeta = attinmeta;
relname = PG_GETARG_TEXT_P(0);
#ifdef MAKERANGEVARFROMNAMELIST_HAS_TWO_ARGS
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname, "pgrowlocks"));
#else
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
#endif
rel = heap_openrv(relrv, AccessShareLock);
scan = heap_beginscan(rel, SnapshotNow, 0, NULL);
mydata = palloc(sizeof(*mydata));
mydata->scan = scan;
mydata->ncolumns = tupdesc->natts;
funcctx->user_fctx = mydata;
MemoryContextSwitchTo(oldcontext);
}
funcctx = SRF_PERCALL_SETUP();
attinmeta = funcctx->attinmeta;
mydata = (MyData *)funcctx->user_fctx;
scan = mydata->scan;
/* scan the relation */
while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
{
/* must hold a buffer lock to call HeapTupleSatisfiesUpdate */
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
if (HeapTupleSatisfiesUpdate(tuple->t_data, GetCurrentCommandId(), scan->rs_cbuf)
== HeapTupleBeingUpdated)
{
char **values;
int i;
values = (char **) palloc(mydata->ncolumns * sizeof(char *));
i = 0;
values[i++] = (char *)DirectFunctionCall1(tidout, PointerGetDatum(&tuple->t_self));
#ifdef HEAP_XMAX_SHARED_LOCK
if (tuple->t_data->t_infomask & HEAP_XMAX_SHARED_LOCK)
values[i++] = pstrdup("Shared");
else
values[i++] = pstrdup("Exclusive");
#else
values[i++] = pstrdup("Exclusive");
#endif
values[i] = palloc(NCHARS*sizeof(char));
snprintf(values[i++], NCHARS, "%d", HeapTupleHeaderGetXmax(tuple->t_data));
#ifdef HEAP_XMAX_SHARED_LOCK
if (tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId *xids;
int nxids;
int j;
int isValidXid = 0; /* any valid xid ever exists? */
values[i++] = pstrdup("true");
nxids = GetMultiXactIdMembers(HeapTupleHeaderGetXmax(tuple->t_data), &xids);
if (nxids == -1)
{
elog(ERROR, "GetMultiXactIdMembers returns error");
}
values[i] = palloc(NCHARS*nxids);
values[i+1] = palloc(NCHARS*nxids);
strcpy(values[i], "{");
strcpy(values[i+1], "{");
for (j=0;j<nxids;j++)
{
char buf[NCHARS];
if (TransactionIdIsInProgress(xids[j]))
{
if (isValidXid)
{
strcat(values[i], ",");
strcat(values[i+1], ",");
}
snprintf(buf, NCHARS, "%d", xids[j]);
strcat(values[i], buf);
snprintf(buf, NCHARS, "%d", BackendXidGetPid(xids[j]));
strcat(values[i+1], buf);
isValidXid = 1;
}
}
strcat(values[i], "}");
strcat(values[i+1], "}");
i++;
}
else
{
values[i++] = pstrdup("false");
values[i] = palloc(NCHARS*sizeof(char));
snprintf(values[i++], NCHARS, "{%d}", HeapTupleHeaderGetXmax(tuple->t_data));
values[i] = palloc(NCHARS*sizeof(char));
snprintf(values[i++], NCHARS, "{%d}", BackendXidGetPid(HeapTupleHeaderGetXmax(tuple->t_data)));
}
#else
values[i++] = pstrdup("false");
values[i++] = pstrdup("{}");
values[i++] = pstrdup("{}");
#endif
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
/* build a tuple */
tuple = BuildTupleFromCStrings(attinmeta, values);
/* make the tuple into a datum */
result = HeapTupleGetDatum(tuple);
/* Clean up */
for (i = 0; i < mydata->ncolumns; i++)
pfree(values[i]);
pfree(values);
SRF_RETURN_NEXT(funcctx, result);
}
else
{
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
}
}
heap_endscan(scan);
heap_close(scan->rs_rd, AccessShareLock);
SRF_RETURN_DONE(funcctx);
}

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-- Adjust this setting to control where the objects get created.
SET search_path = public;
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
);
CREATE OR REPLACE FUNCTION pgrowlocks(text)
RETURNS setof pgrowlocks_type
AS 'MODULE_PATHNAME', 'pgrowlocks'
LANGUAGE 'C' STRICT;