Allow default transaction isolation level (a.k.a. set session

characteristics) to be set through GUC.

doc/src/sgml/ref/set_transaction.sgml

-<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.3 2000/11/24 20:16:38 petere Exp $ -->
+<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.4 2001/06/30 22:03:25 petere Exp $ -->
 <refentry id="SQL-SET-TRANSACTION">
  <docinfo>
   <date>2000-11-24</date>
@@ -74,6 +74,18 @@ SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL { READ COMMITTED | SE
   </para>
  </refsect1>
 
+ <refsect1>
+  <title>Notes</title>
+
+  <para>
+   The session default transaction isolation level can also be set
+   with the command <literal>SET default_transaction_isolation =
+   '<replaceable>value</replaceable>'</literal> and in the
+   configuration file.  Consult the <citetitle>Administrator's
+   Guide</citetitle> for more information.
+  </para>
+ </refsect1>
+
  <refsect1 id="R1-SQL-SET-TRANSACTION-3">
   <title>Compatibility</title>
 

doc/src/sgml/runtime.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.71 2001/06/30 21:15:57 darcy Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.72 2001/06/30 22:03:25 petere Exp $
 -->
 
 <Chapter Id="runtime">
@@ -996,6 +996,29 @@ env PGOPTIONS='-c geqo=off' psql
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <indexterm>
+       <primary>transaction isolation level</primary>
+      </indexterm>
+
+      <term>DEFAUL_TRANSACTION_ISOLATION (<type>string</type>)</term>
+      <listitem>
+       <para>
+        Each SQL transaction has an isolation level, which can be
+        either <quote>read committed</quote> or
+        <quote>serializable</quote>.  This parameter controls what the
+        isolation level of each new transaction is set to.  The
+        default is read committed.
+       </para>
+
+       <para>
+        Consult the <citetitle>PostgreSQL User's Guide</citetitle> and
+        the command <command>SET TRANSACTION</command> for more
+        information.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term>DYNAMIC_LIBRARY_PATH (<type>string</type>)</term>
       <listitem>
@@ -1051,9 +1074,9 @@ dynamic_library_path = '/usr/local/lib:/home/my_project/lib:$libdir:$libdir/cont
         will use the <function>fsync()</> system call in several
         places to make sure that updates are physically written to
         disk and do not hang around in the kernel buffer cache. This
-        increases the chance that a database installation will still
-        be usable after an operating system or hardware crash by a
-        large amount. (Crashes of the database server itself do
+        increases the chance by a large amount that a database
+        installation will still be usable after an operating system or
+        hardware crash.  (Crashes of the database server itself do
         <emphasis>not</> affect this consideration.)
        </para>
 

src/backend/commands/variable.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.50 2001/06/12 22:54:05 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.51 2001/06/30 22:03:25 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -46,9 +46,6 @@ static bool show_timezone(void);
 static bool reset_timezone(void);
 static bool parse_timezone(char *);
 
-static bool show_DefaultXactIsoLevel(void);
-static bool reset_DefaultXactIsoLevel(void);
-static bool parse_DefaultXactIsoLevel(char *);
 static bool show_XactIsoLevel(void);
 static bool reset_XactIsoLevel(void);
 static bool parse_XactIsoLevel(char *);
@@ -448,69 +445,6 @@ reset_timezone(void)
 
 /* SET TRANSACTION */
 
-static bool
-parse_DefaultXactIsoLevel(char *value)
-{
-#if 0
-	TransactionState s = CurrentTransactionState;
-
-#endif
-
-	if (value == NULL)
-	{
-		reset_DefaultXactIsoLevel();
-		return TRUE;
-	}
-
-#if 0
-	if (s->state != TRANS_DEFAULT)
-	{
-		elog(ERROR, "ALTER SESSION/SET TRANSACTION ISOLATION LEVEL"
-			 " can not be called within a transaction");
-		return TRUE;
-	}
-#endif
-
-	if (strcasecmp(value, "SERIALIZABLE") == 0)
-		DefaultXactIsoLevel = XACT_SERIALIZABLE;
-	else if (strcasecmp(value, "COMMITTED") == 0)
-		DefaultXactIsoLevel = XACT_READ_COMMITTED;
-	else
-		elog(ERROR, "Bad TRANSACTION ISOLATION LEVEL (%s)", value);
-
-	return TRUE;
-}
-
-static bool
-show_DefaultXactIsoLevel(void)
-{
-
-	if (DefaultXactIsoLevel == XACT_SERIALIZABLE)
-		elog(NOTICE, "Default TRANSACTION ISOLATION LEVEL is SERIALIZABLE");
-	else
-		elog(NOTICE, "Default TRANSACTION ISOLATION LEVEL is READ COMMITTED");
-	return TRUE;
-}
-
-static bool
-reset_DefaultXactIsoLevel(void)
-{
-#if 0
-	TransactionState s = CurrentTransactionState;
-
-	if (s->state != TRANS_DEFAULT)
-	{
-		elog(ERROR, "ALTER SESSION/SET TRANSACTION ISOLATION LEVEL"
-			 " can not be called within a transaction");
-		return TRUE;
-	}
-#endif
-
-	DefaultXactIsoLevel = XACT_READ_COMMITTED;
-
-	return TRUE;
-}
-
 static bool
 parse_XactIsoLevel(char *value)
 {
@@ -530,7 +464,7 @@ parse_XactIsoLevel(char *value)
 
 	if (strcasecmp(value, "SERIALIZABLE") == 0)
 		XactIsoLevel = XACT_SERIALIZABLE;
-	else if (strcasecmp(value, "COMMITTED") == 0)
+	else if (strcasecmp(value, "READ COMMITTED") == 0)
 		XactIsoLevel = XACT_READ_COMMITTED;
 	else
 		elog(ERROR, "Bad TRANSACTION ISOLATION LEVEL (%s)", value);
@@ -711,8 +645,6 @@ SetPGVariable(const char *name, const char *value)
 		parse_datestyle(mvalue);
 	else if (strcasecmp(name, "timezone") == 0)
 		parse_timezone(mvalue);
-	else if (strcasecmp(name, "DefaultXactIsoLevel") == 0)
-		parse_DefaultXactIsoLevel(mvalue);
 	else if (strcasecmp(name, "XactIsoLevel") == 0)
 		parse_XactIsoLevel(mvalue);
 	else if (strcasecmp(name, "client_encoding") == 0)
@@ -737,8 +669,6 @@ GetPGVariable(const char *name)
 		show_datestyle();
 	else if (strcasecmp(name, "timezone") == 0)
 		show_timezone();
-	else if (strcasecmp(name, "DefaultXactIsoLevel") == 0)
-		show_DefaultXactIsoLevel();
 	else if (strcasecmp(name, "XactIsoLevel") == 0)
 		show_XactIsoLevel();
 	else if (strcasecmp(name, "client_encoding") == 0)
@@ -752,7 +682,6 @@ GetPGVariable(const char *name)
 		ShowAllGUCConfig();
 		show_datestyle();
 		show_timezone();
-		show_DefaultXactIsoLevel();
 		show_XactIsoLevel();
 		show_client_encoding();
 		show_server_encoding();
@@ -772,8 +701,6 @@ ResetPGVariable(const char *name)
 		reset_datestyle();
 	else if (strcasecmp(name, "timezone") == 0)
 		reset_timezone();
-	else if (strcasecmp(name, "DefaultXactIsoLevel") == 0)
-		reset_DefaultXactIsoLevel();
 	else if (strcasecmp(name, "XactIsoLevel") == 0)
 		reset_XactIsoLevel();
 	else if (strcasecmp(name, "client_encoding") == 0)
@@ -784,8 +711,6 @@ ResetPGVariable(const char *name)
 		reset_random_seed();
 	else if (strcasecmp(name, "all") == 0)
 	{
-		reset_DefaultXactIsoLevel();
-		reset_XactIsoLevel();
 		reset_random_seed();
 		/* reset_server_encoding(); */
 		reset_client_encoding();
@@ -793,7 +718,8 @@ ResetPGVariable(const char *name)
 		reset_timezone();
 
 		ResetAllOptions(false);
-	} else
+	}
+	else
 		SetConfigOption(name, NULL,
 						superuser() ? PGC_SUSET : PGC_USERSET,
 						false);

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.232 2001/06/23 00:07:34 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.233 2001/06/30 22:03:25 petere Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -752,7 +752,7 @@ VariableSetStmt:  SET ColId TO var_value
         | SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL opt_level
 				{
 					VariableSetStmt *n = makeNode(VariableSetStmt);
-					n->name  = "DefaultXactIsoLevel";
+					n->name  = "default_transaction_isolation";
 					n->value = $8;
 					$$ = (Node *) n;
 				}
@@ -772,7 +772,7 @@ VariableSetStmt:  SET ColId TO var_value
 				}
 		;
 
-opt_level:  READ COMMITTED					{ $$ = "committed"; }
+opt_level:  READ COMMITTED					{ $$ = "read committed"; }
 		| SERIALIZABLE						{ $$ = "serializable"; }
 		;
 

src/backend/utils/misc/guc.c

@@ -4,7 +4,7 @@
  * Support for grand unified configuration scheme, including SET
  * command, configuration file, and command line options.
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.43 2001/06/27 23:31:39 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.44 2001/06/30 22:03:26 petere Exp $
  *
  * Copyright 2000 by PostgreSQL Global Development Group
  * Written by Peter Eisentraut <peter_e@gmx.net>.
@@ -51,6 +51,11 @@ extern char *Syslog_ident;
 static bool check_facility(const char *facility);
 #endif
 
+static char *default_iso_level_string;
+
+static bool check_defaultxactisolevel(const char *value);
+static void assign_defaultxactisolevel(const char *value);
+
 /*
  * Debugging options
  */
@@ -355,6 +360,9 @@ static struct config_real
 static struct config_string
 			ConfigureNamesString[] =
 {
+	{"default_transaction_isolation", PGC_USERSET, &default_iso_level_string,
+	 "read committed", check_defaultxactisolevel, assign_defaultxactisolevel},
+
 	{"dynamic_library_path", PGC_SUSET, &Dynamic_library_path,
 	 "$libdir", NULL, NULL},
 
@@ -1092,3 +1100,25 @@ check_facility(const char *facility)
 }
 
 #endif
+
+
+
+static bool
+check_defaultxactisolevel(const char *value)
+{
+	return (strcasecmp(value, "read committed") == 0
+			|| strcasecmp(value, "serializable") == 0)
+		? true : false;
+}
+
+
+static void
+assign_defaultxactisolevel(const char *value)
+{
+	if (strcasecmp(value, "serializable") == 0)
+		DefaultXactIsoLevel = XACT_SERIALIZABLE;
+	else if (strcasecmp(value, "read committed") == 0)
+		DefaultXactIsoLevel = XACT_READ_COMMITTED;
+	else
+		elog(ERROR, "bogus transaction isolation level");
+}

src/backend/utils/misc/postgresql.conf.sample

@@ -166,6 +166,7 @@
 #
 #	Misc
 #
+#default_transaction_isolation = 'read committed'
 #sql_inheritance = true
 #australian_timezones = false
 #deadlock_timeout = 1000