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peterepetere
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Read-only transactions, as defined in SQL.
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-146
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16 files changed

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‎doc/src/sgml/features.sgml

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@@ -1,5 +1,5 @@
11
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.13 2003/01/10 11:02:41 petere Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.14 2003/01/10 22:03:26 petere Exp $
33
-->
44

55
<appendix id="features">
@@ -642,13 +642,26 @@ $Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.13 2003/01/10 11:02:41 pe
642642
<entry>ROLLBACK statement</entry>
643643
<entry></entry>
644644
</row>
645+
<row>
646+
<entry>E152</entry>
647+
<entry>Core</entry>
648+
<entry>Basic SET TRANSACTION statement</entry>
649+
<entry></entry>
650+
</row>
645651
<row>
646652
<entry>E152-01</entry>
647653
<entry>Core</entry>
648654
<entry>SET TRANSACTION statement: ISOLATION LEVEL SERIALIZABLE
649655
clause</entry>
650656
<entry></entry>
651657
</row>
658+
<row>
659+
<entry>E152-02</entry>
660+
<entry>Core</entry>
661+
<entry>SET TRANSACTION statement: READ ONLY and READ WRITE
662+
clauses</entry>
663+
<entry></entry>
664+
</row>
652665
<row>
653666
<entry>E161</entry>
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<entry>Core</entry>
@@ -1598,19 +1611,6 @@ $Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.13 2003/01/10 11:02:41 pe
15981611
<entry>WITH HOLD cursors</entry>
15991612
<entry>Cursor to stay open across transactions</entry>
16001613
</row>
1601-
<row>
1602-
<entry>E152</entry>
1603-
<entry>Core</entry>
1604-
<entry>Basic SET TRANSACTION statement</entry>
1605-
<entry></entry>
1606-
</row>
1607-
<row>
1608-
<entry>E152-02</entry>
1609-
<entry>Core</entry>
1610-
<entry>SET TRANSACTION statement: READ ONLY and READ WRITE
1611-
clauses</entry>
1612-
<entry>Syntax accepted; READ ONLY not supported</entry>
1613-
</row>
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<row>
16151615
<entry>E153</entry>
16161616
<entry>Core</entry>

‎doc/src/sgml/ref/set_transaction.sgml

Lines changed: 47 additions & 23 deletions
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@@ -1,4 +1,4 @@
1-
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.9 2002/08/04 04:31:44 momjian Exp $ -->
1+
<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.10 2003/01/10 22:03:27 petere Exp $ -->
22
<refentry id="SQL-SET-TRANSACTION">
33
<docinfo>
44
<date>2000-11-24</date>
@@ -16,27 +16,30 @@
1616

1717
<refsynopsisdiv>
1818
<synopsis>
19-
SET TRANSACTION ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE }
20-
SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
21-
{ READ COMMITTED | SERIALIZABLE }
19+
SET TRANSACTION
20+
[ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
21+
SET SESSION CHARACTERISTICS AS TRANSACTION
22+
[ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
2223
</synopsis>
2324
</refsynopsisdiv>
2425

2526
<refsect1>
2627
<title>Description</title>
2728

2829
<para>
29-
This command sets the transaction isolation level. The
30-
<command>SET TRANSACTION</command> command sets the characteristics
31-
for the current SQL-transaction. It has no effect on any subsequent
32-
transactions. This command cannot be used after the first query or data-modification
33-
statement (<command>SELECT</command>, <command>INSERT</command>,
34-
<command>DELETE</command>, <command>UPDATE</command>,
35-
<command>FETCH</command>, <command>COPY</command>) of a transaction
36-
has been executed. <command>SET SESSION CHARACTERISTICS</command>
37-
sets the default transaction isolation level for each transaction
38-
for a session. <command>SET TRANSACTION</command> can override it
39-
for an individual transaction.
30+
The <command>SET TRANSACTION</command> command sets the transaction
31+
characteristics of the current SQL-transaction. It has no effect on
32+
any subsequent transactions. <command>SET SESSION
33+
CHARACTERISTICS</command> sets the default transaction
34+
characteristics for each transaction of a session. <command>SET
35+
TRANSACTION</command> can override it for an individual
36+
transaction.
37+
</para>
38+
39+
<para>
40+
The available transaction characteristics are the transaction
41+
isolation level and the transaction access mode (read/write or
42+
read-only).
4043
</para>
4144

4245
<para>
@@ -45,7 +48,7 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
4548

4649
<variablelist>
4750
<varlistentry>
48-
<term>READ COMMITTED</term>
51+
<term><literal>READ COMMITTED<literal></term>
4952
<listitem>
5053
<para>
5154
A statement can only see rows committed before it began. This
@@ -55,7 +58,7 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
5558
</varlistentry>
5659

5760
<varlistentry>
58-
<term>SERIALIZABLE</term>
61+
<term><literal>SERIALIZABLE</literal></term>
5962
<listitem>
6063
<para>
6164
The current transaction can only see rows committed before
@@ -72,6 +75,28 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
7275
</listitem>
7376
</varlistentry>
7477
</variablelist>
78+
79+
The transaction isolation level cannot be set after the first query
80+
or data-modification statement (<command>SELECT</command>,
81+
<command>INSERT</command>, <command>DELETE</command>,
82+
<command>UPDATE</command>, <command>FETCH</command>,
83+
<command>COPY</command>) of a transaction has been executed.
84+
</para>
85+
86+
<para>
87+
The transaction access mode determines whether the transaction is
88+
read/write or read-only. Read/write is the default. When a
89+
transaction is read-only, the following SQL commands are
90+
disallowed: <literal>INSERT</literal>, <literal>UPDATE</literal>,
91+
<literal>DELETE</literal>, and <literal>COPY TO</literal> if the
92+
table they would write to is not a temporary table; all
93+
<literal>CREATE</literal>, <literal>ALTER</literal>, and
94+
<literal>DROP</literal> commands; <literal>COMMENT</literal>,
95+
<literal>GRANT</literal>, <literal>REVOKE</literal>,
96+
<literal>TRUNCATE</literal>; and <literal>EXPLAIN ANALYZE</literal>
97+
and <literal>EXECUTE</literal> if the command they would execute is
98+
among those listed. This is a high-level notion of read-only that
99+
does not prevent writes to disk.
75100
</para>
76101
</refsect1>
77102

@@ -97,7 +122,7 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
97122
<title>SQL92, SQL99</title>
98123

99124
<para>
100-
<option>SERIALIZABLE</option> is the default level in
125+
<option>SERIALIZABLE</option> is the default transaction isolation level in
101126
<acronym>SQL</acronym>. <productname>PostgreSQL</productname> does
102127
not provide the isolation levels <option>READ UNCOMMITTED</option>
103128
and <option>REPEATABLE READ</option>. Because of multiversion
@@ -107,11 +132,10 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
107132
</para>
108133

109134
<para>
110-
In <acronym>SQL</acronym> there are two other transaction
111-
characteristics that can be set with these commands: whether the
112-
transaction is read-only and the size of the diagnostics area.
113-
Neither of these concepts are supported in
114-
<productname>PostgreSQL</productname>.
135+
In <acronym>SQL</acronym> there is one other transaction
136+
characteristic that can be set with these commands: the size of
137+
the diagnostics area. This concept is not supported in
138+
<productname>PostgreSQL</productname>.
115139
</para>
116140
</refsect2>
117141
</refsect1>

‎doc/src/sgml/ref/start_transaction.sgml

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@@ -1,5 +1,5 @@
11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.3 2002/08/30 22:45:25 tgl Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.4 2003/01/10 22:03:27 petere Exp $
33
PostgreSQL documentation
44
-->
55

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

2121
<refsynopsisdiv>
2222
<synopsis>
23-
START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ]
23+
START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
2424
</synopsis>
2525

2626
<refsect2 id="R2-SQL-START-TRANSACTION-1">
@@ -77,52 +77,23 @@ WARNING: BEGIN: already a transaction in progress
7777
<title>Description</title>
7878

7979
<para>
80-
This command begins a new transaction. If the isolation level is
81-
specified, the new transaction has that isolation level. In all other
82-
respects, the behavior of this command is identical to the
83-
<xref linkend="sql-begin" endterm="sql-begin-title"> command.
80+
This command begins a new transaction. If the isolation level or
81+
read/write mode is specified, the new transaction has those
82+
characteristics, as if <xref linkend="sql-set-transaction"
83+
endterm="sql-set-transaction-title"> was executed. In all other
84+
respects, the behavior of this command is identical to the <xref
85+
linkend="sql-begin" endterm="sql-begin-title"> command.
8486
</para>
8587

8688
</refsect1>
8789

88-
<refsect1>
89-
<title>Notes</title>
90-
91-
<para>
92-
The isolation level of a transaction can also be set with the <xref
93-
linkend="sql-set-transaction" endterm="sql-set-transaction-title">
94-
command. If no isolation level is specified, the default isolation
95-
level is used.
96-
</para>
97-
</refsect1>
98-
9990
<refsect1 id="R1-SQL-START-TRANSACTION-3">
10091
<title>Compatibility</title>
10192

102-
<refsect2 id="R2-SQL-START-TRANSACTION-4">
103-
<title>SQL99</title>
104-
105-
<para>
106-
<option>SERIALIZABLE</option> is the default isolation level in
107-
<acronym>SQL99</acronym>, but it is not the usual default in
108-
<productname>PostgreSQL</productname>: the factory default setting
109-
is READ COMMITTED.
110-
<productname>PostgreSQL</productname>
111-
does not provide the isolation levels <option>READ UNCOMMITTED</option>
112-
and <option>REPEATABLE READ</option>. Because of lack of predicate
113-
locking, the <option>SERIALIZABLE</option> level is
114-
not truly serializable. See the <citetitle>User's Guide</citetitle>
115-
for details.
116-
</para>
117-
118-
<para>
119-
In <acronym>SQL99</acronym> this statement can specify two other
120-
properties of the new transaction: whether the transaction is
121-
read-only and the size of the diagnostics area. Neither of these
122-
concepts are currently supported in
123-
<productname>PostgreSQL</productname>.
124-
</para>
125-
</refsect2>
93+
<para>
94+
SQL99; but see also the compatibility section of <xref
95+
linkend="sql-set-transaction" endterm="sql-set-transaction-title">.
96+
</para>
12697
</refsect1>
12798
</refentry>
12899

‎doc/src/sgml/release.sgml

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11
<!--
2-
$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.176 2003/01/08 00:22:26 tgl Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.177 2003/01/10 22:03:26 petere Exp $
33
-->
44

55
<appendix id="release">
@@ -36,6 +36,7 @@ System can use either hash- or sort-based strategy for grouped aggregation
3636
ON COMMIT options for temp tables
3737
extra_float_digits option allows pg_dump to dump float data accurately
3838
Long options for psql and pg_dump are now available on all platforms
39+
Read-only transactions
3940
]]></literallayout>
4041

4142
</sect1>

‎src/backend/access/transam/xact.c

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@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.140 2002/11/23 03:59:06 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.141 2003/01/10 22:03:27 petere Exp $
1212
*
1313
* NOTES
1414
* Transaction aborts can now occur two ways:
@@ -208,6 +208,9 @@ TransactionState CurrentTransactionState = &CurrentTransactionStateData;
208208
int DefaultXactIsoLevel = XACT_READ_COMMITTED;
209209
int XactIsoLevel;
210210

211+
bool DefaultXactReadOnly = false;
212+
bool XactReadOnly;
213+
211214
bool autocommit = true;
212215

213216
int CommitDelay = 0; /* precommit delay in microseconds */
@@ -848,6 +851,7 @@ StartTransaction(void)
848851

849852
FreeXactSnapshot();
850853
XactIsoLevel = DefaultXactIsoLevel;
854+
XactReadOnly = DefaultXactReadOnly;
851855

852856
/*
853857
* Check the current transaction state. If the transaction system is

‎src/backend/catalog/namespace.c

Lines changed: 25 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
* Portions Copyright (c) 1994, Regents of the University of California
1414
*
1515
* IDENTIFICATION
16-
* $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.43 2003/01/07 20:56:06 tgl Exp $
16+
* $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.44 2003/01/10 22:03:27 petere Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
@@ -278,6 +278,30 @@ RelnameGetRelid(const char *relname)
278278
return InvalidOid;
279279
}
280280

281+
/*
282+
* RelidGetNamespaceId
283+
* Given a relation OID, return the namespace OID.
284+
*/
285+
Oid
286+
RelidGetNamespaceId(Oid relid)
287+
{
288+
HeapTuple tuple;
289+
Form_pg_class pg_class_form;
290+
Oid result;
291+
292+
tuple = SearchSysCache(RELOID,
293+
ObjectIdGetDatum(relid),
294+
0, 0, 0);
295+
if (!HeapTupleIsValid(tuple))
296+
elog(ERROR, "cache lookup failed for relation %u", relid);
297+
pg_class_form = (Form_pg_class) GETSTRUCT(tuple);
298+
299+
result = pg_class_form->relnamespace;
300+
ReleaseSysCache(tuple);
301+
return result;
302+
}
303+
304+
281305
/*
282306
* RelationIsVisible
283307
* Determine whether a relation (identified by OID) is visible in the

‎src/backend/commands/copy.c

Lines changed: 5 additions & 1 deletion
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@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.187 2002/12/15 16:17:38 tgl Exp $
12+
* $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.188 2003/01/10 22:03:27 petere Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -348,6 +348,10 @@ DoCopy(const CopyStmt *stmt)
348348
*/
349349
rel = heap_openrv(relation, (is_from ? RowExclusiveLock : AccessShareLock));
350350

351+
/* check read-only transaction */
352+
if (XactReadOnly && !is_from && !isTempNamespace(RelationGetNamespace(rel)))
353+
elog(ERROR, "transaction is read-only");
354+
351355
/* Check permissions. */
352356
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
353357
required_access);

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