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Commit9688939

Browse files
committed
Implement isolation levels read uncommitted and repeatable read as acting
like the next higher one.
1 parent144a2ec commit9688939

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15 files changed

+156
-69
lines changed

15 files changed

+156
-69
lines changed

‎doc/src/sgml/mvcc.sgml

Lines changed: 20 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.40 2003/11/04 09:55:38 petere Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.41 2003/11/06 22:08:14 petere Exp $
33
-->
44

55
<chapter id="mvcc">
@@ -206,8 +206,25 @@ $Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.40 2003/11/04 09:55:38 petere
206206
</table>
207207

208208
<para>
209-
<productname>PostgreSQL</productname>
210-
offers the Read Committed and Serializable isolation levels.
209+
In <productname>PostgreSQL</productname>, you can use all four
210+
possible transaction isolation levels. Internally, there are only
211+
two distinct isolation levels, which correspond to the levels Read
212+
Committed and Serializable. When you select the level Read
213+
Uncommitted you really get Read Committed, and when you select
214+
Repeatable Read you really get Serializable, so the actual
215+
isolation level may be stricter than what you select. This is
216+
permitted by the SQL standard: the four isolation levels only
217+
define which phenomena must not happen, they do not define which
218+
phenomena must happen. The reason that PostgreSQL only provides
219+
two isolation levels is that this is the only sensible way to map
220+
the isolation levels to the multiversion concurrency control
221+
architecture. The behavior of the available isolation levels is
222+
detailed in the following subsections.
223+
</para>
224+
225+
<para>
226+
To set the transaction isolation level of a transaction, use the
227+
command <xref linkend="sql-set-transaction">.
211228
</para>
212229

213230
<sect2 id="xact-read-committed">

‎doc/src/sgml/ref/set_transaction.sgml

Lines changed: 17 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.17 2003/09/11 21:42:20 momjian Exp $ -->
1+
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.18 2003/11/06 22:08:14 petere Exp $ -->
22
<refentry id="SQL-SET-TRANSACTION">
33
<refmeta>
44
<refentrytitle id="SQL-SET-TRANSACTION-TITLE">SET TRANSACTION</refentrytitle>
@@ -17,9 +17,12 @@
1717
<refsynopsisdiv>
1818
<synopsis>
1919
SET TRANSACTION
20-
[ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
20+
[ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
21+
[ READ WRITE | READ ONLY ]
22+
2123
SET SESSION CHARACTERISTICS AS TRANSACTION
22-
[ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
24+
[ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
25+
[ READ WRITE | READ ONLY ]
2326
</synopsis>
2427
</refsynopsisdiv>
2528

@@ -76,8 +79,11 @@ SET SESSION CHARACTERISTICS AS TRANSACTION
7679
</varlistentry>
7780
</variablelist>
7881

79-
The transaction isolation level cannot be set after the first query
80-
or data-modification statement (<command>SELECT</command>,
82+
The level <literal>READ UNCOMMITTED</literal> is mapped to
83+
<literal>READ COMMITTED</literal>, the level <literal>REPEATABLE
84+
READ</literal> is mapped to <literal>SERIALIZABLE</literal>, The
85+
transaction isolation level cannot be set after the first query or
86+
data-modification statement (<command>SELECT</command>,
8187
<command>INSERT</command>, <command>DELETE</command>,
8288
<command>UPDATE</command>, <command>FETCH</command>,
8389
<command>COPY</command>) of a transaction has been executed. See
@@ -122,13 +128,12 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
122128
<para>
123129
Both commands are defined in the <acronym>SQL</acronym> standard.
124130
<literal>SERIALIZABLE</literal> is the default transaction
125-
isolation level in the standard; in <productname>PostgreSQL</productname> the default is
126-
ordinarily <literal>READ COMMITTED</literal>, but you can change it as
127-
described above. <productname>PostgreSQL</productname> does not
128-
provide the isolation levels <literal>READ UNCOMMITTED</literal>
129-
and <literal>REPEATABLE READ</literal>. Because of multiversion
130-
concurrency control, the <literal>SERIALIZABLE</literal> level is
131-
not truly serializable. See <xref linkend="mvcc"> for details.
131+
isolation level in the standard; in
132+
<productname>PostgreSQL</productname> the default is ordinarily
133+
<literal>READ COMMITTED</literal>, but you can change it as
134+
described above. Because of multiversion concurrency control, the
135+
<literal>SERIALIZABLE</literal> level is not truly
136+
serializable. See <xref linkend="mvcc"> for details.
132137
</para>
133138

134139
<para>

‎doc/src/sgml/ref/start_transaction.sgml

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.7 2003/09/09 18:28:53 tgl Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.8 2003/11/06 22:08:14 petere Exp $
33
PostgreSQL documentation
44
-->
55

@@ -20,7 +20,9 @@ PostgreSQL documentation
2020

2121
<refsynopsisdiv>
2222
<synopsis>
23-
START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
23+
START TRANSACTION
24+
[ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
25+
[ READ WRITE | READ ONLY ]
2426
</synopsis>
2527
</refsynopsisdiv>
2628

‎doc/src/sgml/runtime.sgml

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.216 2003/11/04 09:55:38 petere Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.217 2003/11/06 22:08:14 petere Exp $
33
-->
44

55
<Chapter Id="runtime">
@@ -2043,10 +2043,12 @@ SET ENABLE_SEQSCAN TO OFF;
20432043
<term><varname>default_transaction_isolation</varname> (<type>string</type>)</term>
20442044
<listitem>
20452045
<para>
2046-
Each SQL transaction has an isolation level, which can be either
2047-
<quote>read committed</quote> or <quote>serializable</quote>.
2048-
This parameter controls the default isolation level of each new
2049-
transaction. The default is <quote>read committed</quote>.
2046+
Each SQL transaction has an isolation level, which can be
2047+
either <quote>read uncommitted</quote>, <quote>read
2048+
committed</quote>, <quote>repeatable read</quote>, or
2049+
<quote>serializable</quote>. This parameter controls the
2050+
default isolation level of each new transaction. The default
2051+
is <quote>read committed</quote>.
20502052
</para>
20512053

20522054
<para>

‎src/backend/catalog/sql_features.txt

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -156,10 +156,10 @@ F051Basic date and time07LOCALTIMEYES
156156
F051Basic date and time08LOCALTIMESTAMPYES
157157
F052Intervals and datetime arithmeticYES
158158
F081UNION and EXCEPT in viewsYES
159-
F111Isolation levels other than SERIALIZABLENO
160-
F111Isolation levels other than SERIALIZABLE01READ UNCOMMITTED isolation levelNO
159+
F111Isolation levels other than SERIALIZABLEYES
160+
F111Isolation levels other than SERIALIZABLE01READ UNCOMMITTED isolation levelYESbehaves like READ COMMITTED
161161
F111Isolation levels other than SERIALIZABLE02READ COMMITTED isolation levelYES
162-
F111Isolation levels other than SERIALIZABLE03REPEATABLE READ isolation levelNO
162+
F111Isolation levels other than SERIALIZABLE03REPEATABLE READ isolation levelYESbehaves like SERIALIZABLE
163163
F121Basic diagnostics managementNO
164164
F121Basic diagnostics management01GET DIAGNOSTICS statementNO
165165
F121Basic diagnostics management02SET TRANSACTION statement: DIAGNOSTICS SIZE clauseNO

‎src/backend/commands/trigger.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.159 2003/10/02 06:34:03 petere Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.160 2003/11/06 22:08:14 petere Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -1576,7 +1576,7 @@ ltrmark:;
15761576

15771577
caseHeapTupleUpdated:
15781578
ReleaseBuffer(buffer);
1579-
if (XactIsoLevel==XACT_SERIALIZABLE)
1579+
if (IsXactIsoLevelSerializable)
15801580
ereport(ERROR,
15811581
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
15821582
errmsg("could not serialize access due to concurrent update")));

‎src/backend/commands/variable.c

Lines changed: 24 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.88 2003/09/25 06:57:59 petere Exp $
12+
* $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.89 2003/11/06 22:08:14 petere Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -640,11 +640,21 @@ assign_XactIsoLevel(const char *value, bool doit, bool interactive)
640640
if (doit)
641641
XactIsoLevel=XACT_SERIALIZABLE;
642642
}
643+
elseif (strcmp(value,"repeatable read")==0)
644+
{
645+
if (doit)
646+
XactIsoLevel=XACT_REPEATABLE_READ;
647+
}
643648
elseif (strcmp(value,"read committed")==0)
644649
{
645650
if (doit)
646651
XactIsoLevel=XACT_READ_COMMITTED;
647652
}
653+
elseif (strcmp(value,"read uncommitted")==0)
654+
{
655+
if (doit)
656+
XactIsoLevel=XACT_READ_UNCOMMITTED;
657+
}
648658
elseif (strcmp(value,"default")==0)
649659
{
650660
if (doit)
@@ -659,10 +669,19 @@ assign_XactIsoLevel(const char *value, bool doit, bool interactive)
659669
constchar*
660670
show_XactIsoLevel(void)
661671
{
662-
if (XactIsoLevel==XACT_SERIALIZABLE)
663-
return"serializable";
664-
else
665-
return"read committed";
672+
switch (XactIsoLevel)
673+
{
674+
caseXACT_READ_UNCOMMITTED:
675+
return"read uncommitted";
676+
caseXACT_READ_COMMITTED:
677+
return"read committed";
678+
caseXACT_REPEATABLE_READ:
679+
return"repeatable read";
680+
caseXACT_SERIALIZABLE:
681+
return"serializable";
682+
default:
683+
return"bogus";
684+
}
666685
}
667686

668687

‎src/backend/executor/execMain.c

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -26,7 +26,7 @@
2626
*
2727
*
2828
* IDENTIFICATION
29-
* $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.220 2003/10/01 21:30:52 tgl Exp $
29+
* $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.221 2003/11/06 22:08:14 petere Exp $
3030
*
3131
*-------------------------------------------------------------------------
3232
*/
@@ -1139,7 +1139,7 @@ lnext:;
11391139
break;
11401140

11411141
caseHeapTupleUpdated:
1142-
if (XactIsoLevel==XACT_SERIALIZABLE)
1142+
if (IsXactIsoLevelSerializable)
11431143
ereport(ERROR,
11441144
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
11451145
errmsg("could not serialize access due to concurrent update")));
@@ -1440,7 +1440,7 @@ ldelete:;
14401440
break;
14411441

14421442
caseHeapTupleUpdated:
1443-
if (XactIsoLevel==XACT_SERIALIZABLE)
1443+
if (IsXactIsoLevelSerializable)
14441444
ereport(ERROR,
14451445
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
14461446
errmsg("could not serialize access due to concurrent update")));
@@ -1576,7 +1576,7 @@ lreplace:;
15761576
break;
15771577

15781578
caseHeapTupleUpdated:
1579-
if (XactIsoLevel==XACT_SERIALIZABLE)
1579+
if (IsXactIsoLevelSerializable)
15801580
ereport(ERROR,
15811581
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
15821582
errmsg("could not serialize access due to concurrent update")));

‎src/backend/parser/gram.y

Lines changed: 9 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
*
1212
*
1313
* IDENTIFICATION
14-
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.436 2003/10/02 06:34:04 petere Exp $
14+
* $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.437 2003/11/06 22:08:14 petere Exp $
1515
*
1616
* HISTORY
1717
* AUTHORDATEMAJOR EVENT
@@ -342,7 +342,7 @@ static void doNegateFloat(Value *v);
342342

343343
DATABASE DAY_P DEALLOCATE DEC DECIMAL_P DECLARE DEFAULT DEFAULTS
344344
DEFERRABLE DEFERRED DEFINER DELETE_P DELIMITER DELIMITERS
345-
DESC DISTINCT DO DOMAIN_P DOUBLE_P DROP
345+
DESC DISTINCT DO DOMAIN_P DOUBLE_P DROP
346346

347347
EACH ELSE ENCODING ENCRYPTED END_P ESCAPE EXCEPT EXCLUDING
348348
EXCLUSIVE EXECUTE EXISTS EXPLAIN EXTERNAL EXTRACT
@@ -380,7 +380,7 @@ static void doNegateFloat(Value *v);
380380
PRECISION PRESERVE PREPARE PRIMARY
381381
PRIOR PRIVILEGES PROCEDURAL PROCEDURE
382382

383-
READ REAL RECHECK REFERENCES REINDEX RELATIVE_P RENAME REPLACE
383+
READ REAL RECHECK REFERENCES REINDEX RELATIVE_P RENAMEREPEATABLEREPLACE
384384
RESET RESTART RESTRICT RETURNS REVOKE RIGHT ROLLBACK ROW ROWS
385385
RULE
386386

@@ -393,7 +393,7 @@ static void doNegateFloat(Value *v);
393393
TO TOAST TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
394394
TRUNCATE TRUSTED TYPE_P
395395

396-
UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNTIL
396+
UNCOMMITTEDUNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNTIL
397397
UPDATE USAGE USER USING
398398

399399
VACUUM VALID VALIDATOR VALUES VARCHAR VARYING
@@ -922,7 +922,9 @@ var_value:opt_boolean
922922
{$$ = makeAConst($1); }
923923
;
924924

925-
iso_level:READCOMMITTED{$$ ="read committed"; }
925+
iso_level:READUNCOMMITTED{$$ ="read uncommitted"; }
926+
|READCOMMITTED{$$ ="read committed"; }
927+
|REPEATABLEREAD{$$ ="repeatable read"; }
926928
|SERIALIZABLE{$$ ="serializable"; }
927929
;
928930

@@ -7407,6 +7409,7 @@ unreserved_keyword:
74077409
| REINDEX
74087410
| RELATIVE_P
74097411
| RENAME
7412+
| REPEATABLE
74107413
| REPLACE
74117414
| RESET
74127415
| RESTART
@@ -7445,6 +7448,7 @@ unreserved_keyword:
74457448
| TRUNCATE
74467449
| TRUSTED
74477450
| TYPE_P
7451+
| UNCOMMITTED
74487452
| UNENCRYPTED
74497453
| UNKNOWN
74507454
| UNLISTEN

‎src/backend/parser/keywords.c

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.141 2003/08/04 02:40:01 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.142 2003/11/06 22:08:15 petere Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -251,6 +251,7 @@ static const ScanKeyword ScanKeywords[] = {
251251
{"reindex",REINDEX},
252252
{"relative",RELATIVE_P},
253253
{"rename",RENAME},
254+
{"repeatable",REPEATABLE},
254255
{"replace",REPLACE},
255256
{"reset",RESET},
256257
{"restart",RESTART},
@@ -307,6 +308,7 @@ static const ScanKeyword ScanKeywords[] = {
307308
{"truncate",TRUNCATE},
308309
{"trusted",TRUSTED},
309310
{"type",TYPE_P},
311+
{"uncommitted",UNCOMMITTED},
310312
{"unencrypted",UNENCRYPTED},
311313
{"union",UNION},
312314
{"unique",UNIQUE},

‎src/backend/utils/adt/ri_triggers.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -17,7 +17,7 @@
1717
*
1818
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
1919
*
20-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.63 2003/10/31 03:58:20 wieck Exp $
20+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.64 2003/11/06 22:08:15 petere Exp $
2121
*
2222
* ----------
2323
*/
@@ -3073,7 +3073,7 @@ ri_PerformCheck(RI_QueryKey *qkey, void *qplan,
30733073
* rows under current snapshot that wouldn't be visible per the
30743074
* transaction snapshot).
30753075
*/
3076-
if (XactIsoLevel==XACT_SERIALIZABLE)
3076+
if (IsXactIsoLevelSerializable)
30773077
{
30783078
useCurrentSnapshot=detectNewRows;
30793079
}

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