Read-only transactions, as defined in SQL.

doc/src/sgml/features.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.13 2003/01/10 11:02:41 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.14 2003/01/10 22:03:26 petere Exp $
 -->
 
 <appendix id="features">
@@ -642,6 +642,12 @@ $Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.13 2003/01/10 11:02:41 pe
         <entry>ROLLBACK statement</entry>
         <entry></entry>
        </row>
+       <row>
+        <entry>E152</entry>
+        <entry>Core</entry>
+        <entry>Basic SET TRANSACTION statement</entry>
+        <entry></entry>
+       </row>
        <row>
         <entry>E152-01</entry>
         <entry>Core</entry>
@@ -649,6 +655,13 @@ $Header: /cvsroot/pgsql/doc/src/sgml/features.sgml,v 2.13 2003/01/10 11:02:41 pe
          clause</entry> 
         <entry></entry>
        </row>
+       <row>
+        <entry>E152-02</entry>
+        <entry>Core</entry>
+        <entry>SET TRANSACTION statement: READ ONLY and READ WRITE
+         clauses</entry> 
+        <entry></entry>
+       </row>
        <row>
         <entry>E161</entry>
         <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
         <entry>WITH HOLD cursors</entry>
         <entry>Cursor to stay open across transactions</entry>
        </row>
-       <row>
-        <entry>E152</entry>
-        <entry>Core</entry>
-        <entry>Basic SET TRANSACTION statement</entry>
-        <entry></entry>
-       </row>
-       <row>
-        <entry>E152-02</entry>
-        <entry>Core</entry>
-        <entry>SET TRANSACTION statement: READ ONLY and READ WRITE
-         clauses</entry> 
-        <entry>Syntax accepted; READ ONLY not supported</entry>
-       </row>
        <row>
         <entry>E153</entry>
         <entry>Core</entry>

doc/src/sgml/ref/set_transaction.sgml

-<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.9 2002/08/04 04:31:44 momjian Exp $ -->
+<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.10 2003/01/10 22:03:27 petere Exp $ -->
 <refentry id="SQL-SET-TRANSACTION">
  <docinfo>
   <date>2000-11-24</date>
@@ -16,9 +16,10 @@
 
  <refsynopsisdiv>
   <synopsis>
-SET TRANSACTION ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE }
-SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
-    { READ COMMITTED | SERIALIZABLE }
+SET TRANSACTION
+    [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
+SET SESSION CHARACTERISTICS AS TRANSACTION
+    [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
   </synopsis>
  </refsynopsisdiv>
 
@@ -26,17 +27,19 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
   <title>Description</title>
 
   <para>
-   This command sets the transaction isolation level.  The
-   <command>SET TRANSACTION</command> command sets the characteristics
-   for the current SQL-transaction. It has no effect on any subsequent
-   transactions.  This command cannot be used after the first query or data-modification
-   statement (<command>SELECT</command>, <command>INSERT</command>,
-   <command>DELETE</command>, <command>UPDATE</command>,
-   <command>FETCH</command>, <command>COPY</command>) of a transaction
-   has been executed.  <command>SET SESSION CHARACTERISTICS</command>
-   sets the default transaction isolation level for each transaction
-   for a session.  <command>SET TRANSACTION</command> can override it
-   for an individual transaction.
+   The <command>SET TRANSACTION</command> command sets the transaction
+   characteristics of the current SQL-transaction. It has no effect on
+   any subsequent transactions.  <command>SET SESSION
+   CHARACTERISTICS</command> sets the default transaction
+   characteristics for each transaction of a session.  <command>SET
+   TRANSACTION</command> can override it for an individual
+   transaction.
+  </para>
+
+  <para>
+   The available transaction characteristics are the transaction
+   isolation level and the transaction access mode (read/write or
+   read-only).
   </para>
 
   <para>
@@ -45,7 +48,7 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
 
    <variablelist>
     <varlistentry>
-     <term>READ COMMITTED</term>
+     <term><literal>READ COMMITTED<literal></term>
      <listitem>
       <para>
        A statement can only see rows committed before it began. This
@@ -55,7 +58,7 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
     </varlistentry>
 
     <varlistentry>
-     <term>SERIALIZABLE</term>
+     <term><literal>SERIALIZABLE</literal></term>
      <listitem>
       <para>
        The current transaction can only see rows committed before
@@ -72,6 +75,28 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL
      </listitem>
     </varlistentry>
    </variablelist>
+
+   The transaction isolation level cannot be set after the first query
+   or data-modification statement (<command>SELECT</command>,
+   <command>INSERT</command>, <command>DELETE</command>,
+   <command>UPDATE</command>, <command>FETCH</command>,
+   <command>COPY</command>) of a transaction has been executed.
+  </para>
+
+  <para>
+   The transaction access mode determines whether the transaction is
+   read/write or read-only.  Read/write is the default.  When a
+   transaction is read-only, the following SQL commands are
+   disallowed: <literal>INSERT</literal>, <literal>UPDATE</literal>,
+   <literal>DELETE</literal>, and <literal>COPY TO</literal> if the
+   table they would write to is not a temporary table; all
+   <literal>CREATE</literal>, <literal>ALTER</literal>, and
+   <literal>DROP</literal> commands; <literal>COMMENT</literal>,
+   <literal>GRANT</literal>, <literal>REVOKE</literal>,
+   <literal>TRUNCATE</literal>; and <literal>EXPLAIN ANALYZE</literal>
+   and <literal>EXECUTE</literal> if the command they would execute is
+   among those listed.  This is a high-level notion of read-only that
+   does not prevent writes to disk.
   </para>
  </refsect1>
 
@@ -97,7 +122,7 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
    <title>SQL92, SQL99</title>
 
    <para>
-    <option>SERIALIZABLE</option> is the default level in
+    <option>SERIALIZABLE</option> is the default transaction isolation level in
     <acronym>SQL</acronym>.  <productname>PostgreSQL</productname> does
     not provide the isolation levels <option>READ UNCOMMITTED</option> 
     and <option>REPEATABLE READ</option>. Because of multiversion
@@ -107,10 +132,9 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
    </para>
 
    <para>
-    In <acronym>SQL</acronym> there are two other transaction
-    characteristics that can be set with these commands: whether the
-    transaction is read-only and the size of the diagnostics area.
-    Neither of these concepts are supported in
+    In <acronym>SQL</acronym> there is one other transaction
+    characteristic that can be set with these commands: the size of
+    the diagnostics area.  This concept is not supported in
     <productname>PostgreSQL</productname>.
    </para>
   </refsect2>

doc/src/sgml/ref/start_transaction.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.3 2002/08/30 22:45:25 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.4 2003/01/10 22:03:27 petere Exp $
 PostgreSQL documentation
 -->
 
@@ -20,7 +20,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
   <synopsis>
-START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ]
+START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
   </synopsis>
 
   <refsect2 id="R2-SQL-START-TRANSACTION-1">
@@ -77,52 +77,23 @@ WARNING:  BEGIN: already a transaction in progress
   <title>Description</title>
 
   <para>
-   This command begins a new transaction. If the isolation level is
-   specified, the new transaction has that isolation level. In all other
-   respects, the behavior of this command is identical to the
-   <xref linkend="sql-begin" endterm="sql-begin-title"> command.
+   This command begins a new transaction. If the isolation level or
+   read/write mode is specified, the new transaction has those
+   characteristics, as if <xref linkend="sql-set-transaction"
+   endterm="sql-set-transaction-title"> was executed. In all other
+   respects, the behavior of this command is identical to the <xref
+   linkend="sql-begin" endterm="sql-begin-title"> command.
   </para>
 
  </refsect1>
 
- <refsect1>
-  <title>Notes</title>
-
-  <para>
-   The isolation level of a transaction can also be set with the <xref
-   linkend="sql-set-transaction" endterm="sql-set-transaction-title">
-   command. If no isolation level is specified, the default isolation
-   level is used.
-  </para>
- </refsect1>
-
  <refsect1 id="R1-SQL-START-TRANSACTION-3">
   <title>Compatibility</title>
 
-  <refsect2 id="R2-SQL-START-TRANSACTION-4">
-   <title>SQL99</title>
-
   <para>
-    <option>SERIALIZABLE</option> is the default isolation level in
-    <acronym>SQL99</acronym>, but it is not the usual default in
-    <productname>PostgreSQL</productname>: the factory default setting
-    is READ COMMITTED.
-    <productname>PostgreSQL</productname> 
-    does not provide the isolation levels <option>READ UNCOMMITTED</option>
-    and <option>REPEATABLE READ</option>. Because of lack of predicate
-    locking, the <option>SERIALIZABLE</option> level is
-    not truly serializable. See the <citetitle>User's Guide</citetitle>
-    for details.
+   SQL99; but see also the compatibility section of <xref
+   linkend="sql-set-transaction" endterm="sql-set-transaction-title">.
   </para>
-
-   <para>
-    In <acronym>SQL99</acronym> this statement can specify two other
-    properties of the new transaction: whether the transaction is
-    read-only and the size of the diagnostics area. Neither of these
-    concepts are currently supported in
-    <productname>PostgreSQL</productname>.
-   </para>
-  </refsect2>
  </refsect1>
 </refentry>
 

doc/src/sgml/release.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.176 2003/01/08 00:22:26 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/release.sgml,v 1.177 2003/01/10 22:03:26 petere Exp $
 -->
 
 <appendix id="release">
@@ -36,6 +36,7 @@ System can use either hash- or sort-based strategy for grouped aggregation
 ON COMMIT options for temp tables
 extra_float_digits option allows pg_dump to dump float data accurately
 Long options for psql and pg_dump are now available on all platforms
+Read-only transactions
 ]]></literallayout>
 
  </sect1>

src/backend/access/transam/xact.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.140 2002/11/23 03:59:06 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.141 2003/01/10 22:03:27 petere Exp $
  *
  * NOTES
  *		Transaction aborts can now occur two ways:
@@ -208,6 +208,9 @@ TransactionState CurrentTransactionState = &CurrentTransactionStateData;
 int			DefaultXactIsoLevel = XACT_READ_COMMITTED;
 int			XactIsoLevel;
 
+bool		DefaultXactReadOnly = false;
+bool		XactReadOnly;
+
 bool		autocommit = true;
 
 int			CommitDelay = 0;	/* precommit delay in microseconds */
@@ -848,6 +851,7 @@ StartTransaction(void)
 
 	FreeXactSnapshot();
 	XactIsoLevel = DefaultXactIsoLevel;
+	XactReadOnly = DefaultXactReadOnly;
 
 	/*
 	 * Check the current transaction state.  If the transaction system is

src/backend/catalog/namespace.c

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.43 2003/01/07 20:56:06 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/namespace.c,v 1.44 2003/01/10 22:03:27 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -278,6 +278,30 @@ RelnameGetRelid(const char *relname)
 	return InvalidOid;
 }
 
+/*
+ * RelidGetNamespaceId
+ *		Given a relation OID, return the namespace OID.
+ */
+Oid
+RelidGetNamespaceId(Oid relid)
+{
+	HeapTuple	tuple;
+	Form_pg_class pg_class_form;
+	Oid			result;
+
+	tuple = SearchSysCache(RELOID,
+						   ObjectIdGetDatum(relid),
+						   0, 0, 0);
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "cache lookup failed for relation %u", relid);
+	pg_class_form = (Form_pg_class) GETSTRUCT(tuple);
+
+	result = pg_class_form->relnamespace;
+	ReleaseSysCache(tuple);
+	return result;
+}
+
+
 /*
  * RelationIsVisible
  *		Determine whether a relation (identified by OID) is visible in the

src/backend/commands/copy.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.187 2002/12/15 16:17:38 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/copy.c,v 1.188 2003/01/10 22:03:27 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -348,6 +348,10 @@ DoCopy(const CopyStmt *stmt)
 	 */
 	rel = heap_openrv(relation, (is_from ? RowExclusiveLock : AccessShareLock));
 
+	/* check read-only transaction */
+	if (XactReadOnly && !is_from && !isTempNamespace(RelationGetNamespace(rel)))
+		elog(ERROR, "transaction is read-only");
+
 	/* Check permissions. */
 	aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
 								  required_access);

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.196 2003/01/08 23:32:29 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.197 2003/01/10 22:03:27 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -85,6 +85,7 @@ static void ExecUpdate(TupleTableSlot *slot, ItemPointer tupleid,
 static TupleTableSlot *EvalPlanQualNext(EState *estate);
 static void EndEvalPlanQual(EState *estate);
 static void ExecCheckRTEPerms(RangeTblEntry *rte, CmdType operation);
+static void ExecCheckXactReadOnly(Query *parsetree, CmdType operation);
 static void EvalPlanQualStart(evalPlanQual *epq, EState *estate,
 							  evalPlanQual *priorepq);
 static void EvalPlanQualStop(evalPlanQual *epq);
@@ -201,6 +202,14 @@ ExecutorRun(QueryDesc *queryDesc,
 	operation = queryDesc->operation;
 	dest = queryDesc->dest;
 
+	/*
+	 * If the transaction is read-only, we need to check if any writes
+	 * are planned to non-temporary tables.  This is done here at this
+	 * rather late stage so that we can handle EXPLAIN vs. EXPLAIN
+	 * ANALYZE easily.
+	 */
+	ExecCheckXactReadOnly(queryDesc->parsetree, operation);
+
 	/*
 	 * startup tuple receiver
 	 */
@@ -385,6 +394,45 @@ ExecCheckRTEPerms(RangeTblEntry *rte, CmdType operation)
  */
 
 
+static void
+ExecCheckXactReadOnly(Query *parsetree, CmdType operation)
+{
+	if (!XactReadOnly)
+		return;
+
+	/* CREATE TABLE AS or SELECT INTO */
+	if (operation == CMD_SELECT && parsetree->into != NULL)
+		goto fail;
+
+	if (operation == CMD_DELETE || operation == CMD_INSERT
+		|| operation == CMD_UPDATE)
+	{
+		List *lp;
+
+		foreach(lp, parsetree->rtable)
+		{
+			RangeTblEntry *rte = lfirst(lp);
+
+			if (rte->rtekind != RTE_RELATION)
+				continue;
+
+			if (!rte->checkForWrite)
+				continue;
+
+			if (isTempNamespace(RelidGetNamespaceId(rte->relid)))
+				continue;
+
+			goto fail;
+		}
+	}
+
+	return;
+
+fail:
+	elog(ERROR, "transaction is read-only");
+}
+
+
 /* ----------------------------------------------------------------
  *		InitPlan
  *

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.394 2003/01/10 21:08:13 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.395 2003/01/10 22:03:27 petere Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -162,7 +162,7 @@ static void doNegateFloat(Value *v);
 %type <defelt>	createdb_opt_item copy_opt_item
 
 %type <ival>	opt_lock lock_type cast_context
-%type <boolean>	opt_force opt_or_replace
+%type <boolean>	opt_force opt_or_replace transaction_access_mode
 
 %type <list>	user_list
 
@@ -215,7 +215,8 @@ static void doNegateFloat(Value *v);
 				target_list update_target_list insert_column_list
 				insert_target_list def_list opt_indirection
 				group_clause TriggerFuncArgs select_limit
-				opt_select_limit opclass_item_list trans_options
+				opt_select_limit opclass_item_list transaction_mode_list
+				transaction_mode_list_or_empty
 				TableFuncElementList
 				prep_type_clause prep_type_list
 				execute_param_clause
@@ -863,18 +864,18 @@ set_rest:  ColId TO var_list_or_default
 						n->args = makeList1($3);
 					$$ = n;
 				}
-			| TRANSACTION ISOLATION LEVEL iso_level opt_mode
+			| TRANSACTION transaction_mode_list
 				{
 					VariableSetStmt *n = makeNode(VariableSetStmt);
-					n->name = "TRANSACTION ISOLATION LEVEL";
-					n->args = makeList1(makeStringConst($4, NULL));
+					n->name = "TRANSACTION";
+					n->args = $2;
 					$$ = n;
 				}
-			| SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL iso_level
+			| SESSION CHARACTERISTICS AS TRANSACTION transaction_mode_list
 				{
 					VariableSetStmt *n = makeNode(VariableSetStmt);
-					n->name = "default_transaction_isolation";
-					n->args = makeList1(makeStringConst($7, NULL));
+					n->name = "SESSION CHARACTERISTICS";
+					n->args = $5;
 					$$ = n;
 				}
 			| NAMES opt_encoding
@@ -922,16 +923,6 @@ iso_level:	READ COMMITTED							{ $$ = "read committed"; }
 			| SERIALIZABLE							{ $$ = "serializable"; }
 		;
 
-opt_mode:  READ WRITE
-				{}
-		| READ ONLY
-				{
-					elog(ERROR, "SET TRANSACTION/READ ONLY not yet supported");
-				}
-		| /*EMPTY*/
-				{}
-		;
-
 opt_boolean:
 			TRUE_P									{ $$ = "true"; }
 			| FALSE_P								{ $$ = "false"; }
@@ -1020,7 +1011,7 @@ VariableShowStmt:
 			| SHOW TRANSACTION ISOLATION LEVEL
 				{
 					VariableShowStmt *n = makeNode(VariableShowStmt);
-					n->name = "TRANSACTION ISOLATION LEVEL";
+					n->name = "transaction_isolation";
 					$$ = (Node *) n;
 				}
 			| SHOW SESSION AUTHORIZATION
@@ -1053,7 +1044,7 @@ VariableResetStmt:
 			| RESET TRANSACTION ISOLATION LEVEL
 				{
 					VariableResetStmt *n = makeNode(VariableResetStmt);
-					n->name = "TRANSACTION ISOLATION LEVEL";
+					n->name = "transaction_isolation";
 					$$ = (Node *) n;
 				}
 			| RESET SESSION AUTHORIZATION
@@ -3500,42 +3491,42 @@ UnlistenStmt:
  *****************************************************************************/
 
 TransactionStmt:
-			ABORT_TRANS opt_trans
+			ABORT_TRANS opt_transaction
 				{
 					TransactionStmt *n = makeNode(TransactionStmt);
 					n->command = ROLLBACK;
 					n->options = NIL;
 					$$ = (Node *)n;
 				}
-			| BEGIN_TRANS opt_trans
+			| BEGIN_TRANS opt_transaction
 				{
 					TransactionStmt *n = makeNode(TransactionStmt);
 					n->command = BEGIN_TRANS;
 					n->options = NIL;
 					$$ = (Node *)n;
 				}
-			| START TRANSACTION trans_options
+			| START TRANSACTION transaction_mode_list_or_empty
 				{
 					TransactionStmt *n = makeNode(TransactionStmt);
 					n->command = START;
 					n->options = $3;
 					$$ = (Node *)n;
 				}
-			| COMMIT opt_trans
+			| COMMIT opt_transaction
 				{
 					TransactionStmt *n = makeNode(TransactionStmt);
 					n->command = COMMIT;
 					n->options = NIL;
 					$$ = (Node *)n;
 				}
-			| END_TRANS opt_trans
+			| END_TRANS opt_transaction
 				{
 					TransactionStmt *n = makeNode(TransactionStmt);
 					n->command = COMMIT;
 					n->options = NIL;
 					$$ = (Node *)n;
 				}
-			| ROLLBACK opt_trans
+			| ROLLBACK opt_transaction
 				{
 					TransactionStmt *n = makeNode(TransactionStmt);
 					n->command = ROLLBACK;
@@ -3544,16 +3535,46 @@ TransactionStmt:
 				}
 		;
 
-trans_options:	ISOLATION LEVEL iso_level
-									{ $$ = makeList1(makeStringConst($3, NULL)); }
-			 |	/* EMPTY */			{ $$ = NIL; }
-			 ;
-
-opt_trans:	WORK									{}
+opt_transaction:	WORK							{}
 			| TRANSACTION							{}
 			| /*EMPTY*/								{}
 		;
 
+transaction_mode_list:
+			ISOLATION LEVEL iso_level
+					{ $$ = makeList1(makeDefElem("transaction_isolation",
+												 makeStringConst($3, NULL))); }
+			| transaction_access_mode
+					{ $$ = makeList1(makeDefElem("transaction_read_only",
+												 makeIntConst($1))); }
+			| ISOLATION LEVEL iso_level transaction_access_mode
+					{
+						$$ = makeList2(makeDefElem("transaction_isolation",
+												   makeStringConst($3, NULL)),
+									   makeDefElem("transaction_read_only",
+												   makeIntConst($4)));
+					}
+			| transaction_access_mode ISOLATION LEVEL iso_level
+					{
+						$$ = makeList2(makeDefElem("transaction_read_only",
+												   makeIntConst($1)),
+									   makeDefElem("transaction_isolation",
+												   makeStringConst($4, NULL)));
+					}
+		;
+
+transaction_mode_list_or_empty:
+			transaction_mode_list
+			| /* EMPTY */
+					{ $$ = NIL; }
+		;
+
+transaction_access_mode:
+			READ ONLY { $$ = TRUE; }
+			| READ WRITE { $$ = FALSE; }
+		;
+
+
 /*****************************************************************************
  *
  *		QUERY:

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.188 2003/01/06 00:31:44 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/utility.c,v 1.189 2003/01/10 22:03:28 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -168,6 +168,66 @@ CheckOwnership(RangeVar *rel, bool noCatalogs)
 }
 
 
+static void
+check_xact_readonly(Node *parsetree)
+{
+	if (!XactReadOnly)
+		return;
+
+	/*
+	 * Note: Commands that need to do more complicated checking are
+	 * handled elsewhere.
+	 */
+
+	switch (nodeTag(parsetree))
+	{
+		case T_AlterDatabaseSetStmt:
+		case T_AlterDomainStmt:
+		case T_AlterGroupStmt:
+		case T_AlterTableStmt:
+		case T_RenameStmt:
+		case T_AlterUserStmt:
+		case T_AlterUserSetStmt:
+		case T_CommentStmt:
+		case T_DefineStmt:
+		case T_CreateCastStmt:
+		case T_CreateConversionStmt:
+		case T_CreatedbStmt:
+		case T_CreateDomainStmt:
+		case T_CreateFunctionStmt:
+		case T_CreateGroupStmt:
+		case T_IndexStmt:
+		case T_CreatePLangStmt:
+		case T_CreateOpClassStmt:
+		case T_RuleStmt:
+		case T_CreateSchemaStmt:
+		case T_CreateSeqStmt:
+		case T_CreateStmt:
+		case T_CreateTrigStmt:
+		case T_CompositeTypeStmt:
+		case T_CreateUserStmt:
+		case T_ViewStmt:
+		case T_RemoveAggrStmt:
+		case T_DropCastStmt:
+		case T_DropStmt:
+		case T_DropdbStmt:
+		case T_RemoveFuncStmt:
+		case T_DropGroupStmt:
+		case T_DropPLangStmt:
+		case T_RemoveOperStmt:
+		case T_RemoveOpClassStmt:
+		case T_DropPropertyStmt:
+		case T_DropUserStmt:
+		case T_GrantStmt:
+		case T_TruncateStmt:
+			elog(ERROR, "transaction is read-only");
+			break;
+		default:
+			/*nothing*/;
+	}
+}
+
+
 /*
  * ProcessUtility
  *		general utility function invoker
@@ -187,6 +247,8 @@ ProcessUtility(Node *parsetree,
 			   CommandDest dest,
 			   char *completionTag)
 {
+	check_xact_readonly(parsetree);
+
 	if (completionTag)
 		completionTag[0] = '\0';
 
@@ -214,16 +276,21 @@ ProcessUtility(Node *parsetree,
 						{
 							BeginTransactionBlock();
 
-							/*
-							 * Currently, the only option that can be set
-							 * by START TRANSACTION is the isolation
-							 * level.
-							 */
 							if (stmt->options)
 							{
-								SetPGVariable("TRANSACTION ISOLATION LEVEL",
-											  stmt->options,
-											  false);
+								List *head;
+
+								foreach(head, stmt->options)
+								{
+									DefElem *item = (DefElem *) lfirst(head);
+
+									if (strcmp(item->defname, "transaction_isolation")==0)
+										SetPGVariable("transaction_isolation",
+													  makeList1(item->arg), false);
+									else if (strcmp(item->defname, "transaction_read_only")==0)
+										SetPGVariable("transaction_read_only",
+													  makeList1(item->arg), false);
+								}
 							}
 						}
 						break;
@@ -765,6 +832,44 @@ ProcessUtility(Node *parsetree,
 			{
 				VariableSetStmt *n = (VariableSetStmt *) parsetree;
 
+				/*
+				 * Special cases for special SQL syntax that
+				 * effectively sets more than one variable per
+				 * statement.
+				 */
+				if (strcmp(n->name, "TRANSACTION")==0)
+				{
+					List *head;
+
+					foreach(head, n->args)
+					{
+						DefElem *item = (DefElem *) lfirst(head);
+
+						if (strcmp(item->defname, "transaction_isolation")==0)
+							SetPGVariable("transaction_isolation",
+										  makeList1(item->arg), n->is_local);
+						else if (strcmp(item->defname, "transaction_read_only")==0)
+							SetPGVariable("transaction_read_only",
+										  makeList1(item->arg), n->is_local);
+					}
+				}
+				else if (strcmp(n->name, "SESSION CHARACTERISTICS")==0)
+				{
+					List *head;
+
+					foreach(head, n->args)
+					{
+						DefElem *item = (DefElem *) lfirst(head);
+
+						if (strcmp(item->defname, "transaction_isolation")==0)
+							SetPGVariable("default_transaction_isolation",
+										  makeList1(item->arg), n->is_local);
+						else if (strcmp(item->defname, "transaction_read_only")==0)
+							SetPGVariable("default_transaction_read_only",
+										  makeList1(item->arg), n->is_local);
+					}
+				}
+				else
 					SetPGVariable(n->name, n->args, n->is_local);
 			}
 			break;

src/backend/utils/misc/guc.c

@@ -5,7 +5,7 @@
  * command, configuration file, and command line options.
  * See src/backend/utils/misc/README for more information.
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.109 2002/12/27 14:06:34 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.110 2003/01/10 22:03:29 petere Exp $
  *
  * Copyright 2000 by PostgreSQL Global Development Group
  * Written by Peter Eisentraut <peter_e@gmx.net>.
@@ -516,6 +516,14 @@ static struct config_bool
 		{"autocommit", PGC_USERSET}, &autocommit,
 		true, NULL, NULL
 	},
+	{
+		{"default_transaction_read_only", PGC_USERSET}, &DefaultXactReadOnly,
+		false, NULL, NULL
+	},
+	{
+		{"transaction_read_only", PGC_USERSET, GUC_NO_RESET_ALL}, &XactReadOnly,
+		false, NULL, NULL
+	},
 
 	{
 		{NULL, 0}, NULL, false, NULL, NULL
@@ -841,7 +849,7 @@ static struct config_string
 	},
 
 	{
-		{"TRANSACTION ISOLATION LEVEL", PGC_USERSET, GUC_NO_RESET_ALL},
+		{"transaction_isolation", PGC_USERSET, GUC_NO_RESET_ALL},
 		&XactIsoLevel_string,
 		NULL, assign_XactIsoLevel, show_XactIsoLevel
 	},
@@ -1157,10 +1165,12 @@ InitializeGUCOptions(void)
 	guc_string_workspace = NULL;
 
 	/*
-	 * Prevent any attempt to override TRANSACTION ISOLATION LEVEL from
+	 * Prevent any attempt to override the transaction modes from
 	 * non-interactive sources.
 	 */
-	SetConfigOption("TRANSACTION ISOLATION LEVEL", "default",
+	SetConfigOption("transaction_isolation", "default",
+					PGC_POSTMASTER, PGC_S_OVERRIDE);
+	SetConfigOption("transaction_read_only", "no",
 					PGC_POSTMASTER, PGC_S_OVERRIDE);
 
 	/*

src/bin/psql/tab-complete.c

@@ -3,7 +3,7 @@
  *
  * Copyright 2000-2002 by PostgreSQL Global Development Group
  *
- * $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.70 2002/12/13 05:36:24 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/bin/psql/tab-complete.c,v 1.71 2003/01/10 22:03:30 petere Exp $
  */
 
 /*----------------------------------------------------------------------
@@ -212,13 +212,7 @@ psql_completion(char *text, int start, int end)
 		"CONSTRAINTS",
 		"NAMES",
 		"SESSION",
-		"TRANSACTION ISOLATION LEVEL",
-		/* these are treated in backend/commands/variable.c */
-		"DateStyle",
-		"TimeZone",
-		"client_encoding",
-		"server_encoding",
-		"seed",
+		"TRANSACTION",
 
 		/*
 		 * the rest should match USERSET entries in
@@ -229,12 +223,14 @@ psql_completion(char *text, int start, int end)
 		"autocommit",
 		"checkpoint_segments",
 		"checkpoint_timeout",
+		"client_encoding",
 		"client_min_messages",
 		"commit_delay",
 		"commit_siblings",
 		"cpu_index_tuple_cost",
 		"cpu_operator_cost",
 		"cpu_tuple_cost",
+		"DateStyle",
 		"db_user_namespace",
 		"deadlock_timeout",
 		"debug_pretty_print",
@@ -269,7 +265,7 @@ psql_completion(char *text, int start, int end)
 		"lc_messages",
 		"lc_monetary",
 		"lc_numeric",
-		"lc_timeC",
+		"lc_time",
 		"log_connections",
 		"log_duration",
 		"log_min_error_statement",
@@ -294,6 +290,8 @@ psql_completion(char *text, int start, int end)
 		"log_planner_stats",
 		"log_source_port",
 		"log_statement_stats",
+		"seed",
+		"server_encoding",
 		"silent_mode",
 		"sort_mem",
 		"sql_inheritance",
@@ -309,6 +307,7 @@ psql_completion(char *text, int start, int end)
 		"syslog_facility",
 		"syslog_ident",
 		"tcpip_socket",
+		"TimeZone",
 		"trace_notify",
 		"transform_null_equals",
 		"unix_socket_directory",
@@ -817,10 +816,18 @@ psql_completion(char *text, int start, int end)
 			 strcasecmp(prev_wd, "RESET") == 0 ||
 			 strcasecmp(prev_wd, "SHOW") == 0)
 		COMPLETE_WITH_LIST(pgsql_variables);
-	/* Complete "SET TRANSACTION ISOLOLATION LEVEL" */
-	else if (strcasecmp(prev2_wd, "SET") == 0 &&
-			 strcasecmp(prev_wd, "TRANSACTION") == 0)
-		COMPLETE_WITH_CONST("ISOLATION");
+	/* Complete "SET TRANSACTION" */
+	else if ((strcasecmp(prev2_wd, "SET") == 0 &&
+			  strcasecmp(prev_wd, "TRANSACTION") == 0) ||
+			 (strcasecmp(prev4_wd, "SESSION") == 0 &&
+			  strcasecmp(prev3_wd, "CHARACTERISTICS") == 0 &&
+			  strcasecmp(prev2_wd, "AS") == 0 &&
+			  strcasecmp(prev_wd, "TRANSACTION") == 0))
+	{
+		char	   *my_list[] = {"ISOLATION", "READ", NULL};
+
+		COMPLETE_WITH_LIST(my_list);
+	}
 	else if (strcasecmp(prev3_wd, "SET") == 0 &&
 			 strcasecmp(prev2_wd, "TRANSACTION") == 0 &&
 			 strcasecmp(prev_wd, "ISOLATION") == 0)
@@ -840,6 +847,15 @@ psql_completion(char *text, int start, int end)
 			 strcasecmp(prev2_wd, "LEVEL") == 0 &&
 			 strcasecmp(prev_wd, "READ") == 0)
 		COMPLETE_WITH_CONST("COMMITTED");
+	else if ((strcasecmp(prev3_wd, "SET") == 0 ||
+			  strcasecmp(prev3_wd, "AS") == 0) &&
+			 strcasecmp(prev2_wd, "TRANSACTION") == 0 &&
+			 strcasecmp(prev_wd, "READ") == 0)
+	{
+		char	   *my_list[] = {"ONLY", "WRITE", NULL};
+
+		COMPLETE_WITH_LIST(my_list);
+	}
 	/* Complete SET CONSTRAINTS <foo> with DEFERRED|IMMEDIATE */
 	else if (strcasecmp(prev3_wd, "SET") == 0 &&
 			 strcasecmp(prev2_wd, "CONSTRAINTS") == 0)
@@ -853,7 +869,7 @@ psql_completion(char *text, int start, int end)
 			 strcasecmp(prev_wd, "SESSION") == 0)
 	{
 		char	   *my_list[] = {"AUTHORIZATION",
-			"CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL",
+			"CHARACTERISTICS AS TRANSACTION",
 		NULL};
 
 		COMPLETE_WITH_LIST(my_list);

src/include/access/xact.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: xact.h,v 1.48 2002/11/18 01:17:39 tgl Exp $
+ * $Id: xact.h,v 1.49 2003/01/10 22:03:30 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,6 +29,9 @@
 
 extern int	DefaultXactIsoLevel;
 extern int	XactIsoLevel;
+extern bool	DefaultXactReadOnly;
+extern bool	XactReadOnly;
+
 
 /* ----------------
  *		transaction state structure

src/include/catalog/namespace.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: namespace.h,v 1.24 2003/01/07 20:56:07 tgl Exp $
+ * $Id: namespace.h,v 1.25 2003/01/10 22:03:30 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -51,6 +51,7 @@ typedef struct _OpclassCandidateList
 extern Oid	RangeVarGetRelid(const RangeVar *relation, bool failOK);
 extern Oid	RangeVarGetCreationNamespace(const RangeVar *newRelation);
 extern Oid	RelnameGetRelid(const char *relname);
+extern Oid	RelidGetNamespaceId(Oid relid);
 extern bool RelationIsVisible(Oid relid);
 
 extern Oid	TypenameGetTypid(const char *typname);

src/test/regress/expected/transactions.out

@@ -40,3 +40,31 @@ SELECT * FROM aggtest;
   42 |  324.78
 (4 rows)
 
+-- Read-only tests
+CREATE TABLE writetest (a int);
+CREATE TEMPORARY TABLE temptest (a int);
+SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY;
+DROP TABLE writetest; -- fail
+ERROR:  transaction is read-only
+INSERT INTO writetest VALUES (1); -- fail
+ERROR:  transaction is read-only
+SELECT * FROM writetest; -- ok
+ a 
+---
+(0 rows)
+
+DELETE FROM temptest; -- ok
+UPDATE temptest SET a = 0 WHERE a = 1 AND writetest.a = temptest.a; -- ok
+PREPARE test AS UPDATE writetest SET a = 0; -- ok
+EXECUTE test; -- fail
+ERROR:  transaction is read-only
+SELECT * FROM writetest, temptest; -- ok
+ a | a 
+---+---
+(0 rows)
+
+CREATE TABLE test AS SELECT * FROM writetest; -- fail
+ERROR:  transaction is read-only
+START TRANSACTION READ WRITE;
+DROP TABLE writetest; -- ok
+COMMIT;

src/test/regress/sql/transactions.sql

@@ -33,3 +33,24 @@ SELECT oid FROM pg_class WHERE relname = 'disappear';
 -- should have members again 
 SELECT * FROM aggtest;
 
+
+-- Read-only tests
+
+CREATE TABLE writetest (a int);
+CREATE TEMPORARY TABLE temptest (a int);
+
+SET SESSION CHARACTERISTICS AS TRANSACTION READ ONLY;
+
+DROP TABLE writetest; -- fail
+INSERT INTO writetest VALUES (1); -- fail
+SELECT * FROM writetest; -- ok
+DELETE FROM temptest; -- ok
+UPDATE temptest SET a = 0 WHERE a = 1 AND writetest.a = temptest.a; -- ok
+PREPARE test AS UPDATE writetest SET a = 0; -- ok
+EXECUTE test; -- fail
+SELECT * FROM writetest, temptest; -- ok
+CREATE TABLE test AS SELECT * FROM writetest; -- fail
+
+START TRANSACTION READ WRITE;
+DROP TABLE writetest; -- ok
+COMMIT;