Implement isolation levels read uncommitted and repeatable read as acting

like the next higher one.

Author: petere

doc/src/sgml/mvcc.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.40 2003/11/04 09:55:38 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/mvcc.sgml,v 2.41 2003/11/06 22:08:14 petere Exp $
 -->
 
  <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
     </table>
 
    <para>
-    <productname>PostgreSQL</productname>
-    offers the Read Committed and Serializable isolation levels.
+    In <productname>PostgreSQL</productname>, you can use all four
+    possible transaction isolation levels.  Internally, there are only
+    two distinct isolation levels, which correspond to the levels Read
+    Committed and Serializable.  When you select the level Read
+    Uncommitted you really get Read Committed, and when you select
+    Repeatable Read you really get Serializable, so the actual
+    isolation level may be stricter than what you select.  This is
+    permitted by the SQL standard: the four isolation levels only
+    define which phenomena must not happen, they do not define which
+    phenomena must happen.  The reason that PostgreSQL only provides
+    two isolation levels is that this is the only sensible way to map
+    the isolation levels to the multiversion concurrency control
+    architecture.  The behavior of the available isolation levels is
+    detailed in the following subsections.
+   </para>
+
+   <para>
+    To set the transaction isolation level of a transaction, use the
+    command <xref linkend="sql-set-transaction">.
    </para>
 
   <sect2 id="xact-read-committed">

doc/src/sgml/ref/set_transaction.sgml

@@ -1,4 +1,4 @@
-<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.17 2003/09/11 21:42:20 momjian Exp $ -->
+<!-- $Header: /cvsroot/pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.18 2003/11/06 22:08:14 petere Exp $ -->
 <refentry id="SQL-SET-TRANSACTION">
  <refmeta>
   <refentrytitle id="SQL-SET-TRANSACTION-TITLE">SET TRANSACTION</refentrytitle>
@@ -17,9 +17,12 @@
  <refsynopsisdiv>
 <synopsis>
 SET TRANSACTION
-    [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
+    [ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
+    [ READ WRITE | READ ONLY ]
+
 SET SESSION CHARACTERISTICS AS TRANSACTION
-    [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
+    [ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
+    [ READ WRITE | READ ONLY ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -76,8 +79,11 @@ SET SESSION CHARACTERISTICS AS TRANSACTION
     </varlistentry>
    </variablelist>
 
-   The transaction isolation level cannot be set after the first query
-   or data-modification statement (<command>SELECT</command>,
+   The level <literal>READ UNCOMMITTED</literal> is mapped to
+   <literal>READ COMMITTED</literal>, the level <literal>REPEATABLE
+   READ</literal> is mapped to <literal>SERIALIZABLE</literal>, 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.  See
@@ -122,13 +128,12 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
   <para>
    Both commands are defined in the <acronym>SQL</acronym> standard.
    <literal>SERIALIZABLE</literal> is the default transaction
-   isolation level in the standard; in <productname>PostgreSQL</productname> the default is
-   ordinarily <literal>READ COMMITTED</literal>, but you can change it as
-   described above.  <productname>PostgreSQL</productname> does not
-   provide the isolation levels <literal>READ UNCOMMITTED</literal>
-   and <literal>REPEATABLE READ</literal>. Because of multiversion
-   concurrency control, the <literal>SERIALIZABLE</literal> level is
-   not truly serializable. See <xref linkend="mvcc"> for details.
+   isolation level in the standard; in
+   <productname>PostgreSQL</productname> the default is ordinarily
+   <literal>READ COMMITTED</literal>, but you can change it as
+   described above.  Because of multiversion concurrency control, the
+   <literal>SERIALIZABLE</literal> level is not truly
+   serializable. See <xref linkend="mvcc"> for details.
   </para>
 
   <para>

doc/src/sgml/ref/start_transaction.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.7 2003/09/09 18:28:53 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.8 2003/11/06 22:08:14 petere Exp $
 PostgreSQL documentation
 -->
 
@@ -20,7 +20,9 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] [ READ WRITE | READ ONLY ]
+START TRANSACTION
+    [ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
+    [ READ WRITE | READ ONLY ]
 </synopsis>
  </refsynopsisdiv>
 

doc/src/sgml/runtime.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.216 2003/11/04 09:55:38 petere Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.217 2003/11/06 22:08:14 petere Exp $
 -->
 
 <Chapter Id="runtime">
@@ -2043,10 +2043,12 @@ SET ENABLE_SEQSCAN TO OFF;
       <term><varname>default_transaction_isolation</varname> (<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 the default isolation level of each new
-        transaction. The default is <quote>read committed</quote>.
+        Each SQL transaction has an isolation level, which can be
+        either <quote>read uncommitted</quote>, <quote>read
+        committed</quote>, <quote>repeatable read</quote>, or
+        <quote>serializable</quote>.  This parameter controls the
+        default isolation level of each new transaction. The default
+        is <quote>read committed</quote>.
        </para>
 
        <para>

src/backend/catalog/sql_features.txt

@@ -156,10 +156,10 @@ F051	Basic date and time	07	LOCALTIME	YES
 F051	Basic date and time	08	LOCALTIMESTAMP	YES	
 F052	Intervals and datetime arithmetic			YES	
 F081	UNION and EXCEPT in views			YES	
-F111	Isolation levels other than SERIALIZABLE			NO	
-F111	Isolation levels other than SERIALIZABLE	01	READ UNCOMMITTED isolation level	NO	
+F111	Isolation levels other than SERIALIZABLE			YES	
+F111	Isolation levels other than SERIALIZABLE	01	READ UNCOMMITTED isolation level	YES	behaves like READ COMMITTED
 F111	Isolation levels other than SERIALIZABLE	02	READ COMMITTED isolation level	YES	
-F111	Isolation levels other than SERIALIZABLE	03	REPEATABLE READ isolation level	NO	
+F111	Isolation levels other than SERIALIZABLE	03	REPEATABLE READ isolation level	YES	behaves like SERIALIZABLE
 F121	Basic diagnostics management			NO	
 F121	Basic diagnostics management	01	GET DIAGNOSTICS statement	NO	
 F121	Basic diagnostics management	02	SET TRANSACTION statement: DIAGNOSTICS SIZE clause	NO	

src/backend/commands/trigger.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.159 2003/10/02 06:34:03 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.160 2003/11/06 22:08:14 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1576,7 +1576,7 @@ ltrmark:;
 
 			case HeapTupleUpdated:
 				ReleaseBuffer(buffer);
-				if (XactIsoLevel == XACT_SERIALIZABLE)
+				if (IsXactIsoLevelSerializable)
 					ereport(ERROR,
 							(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
 							 errmsg("could not serialize access due to concurrent update")));

src/backend/commands/variable.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.88 2003/09/25 06:57:59 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/variable.c,v 1.89 2003/11/06 22:08:14 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -640,11 +640,21 @@ assign_XactIsoLevel(const char *value, bool doit, bool interactive)
 		if (doit)
 			XactIsoLevel = XACT_SERIALIZABLE;
 	}
+	else if (strcmp(value, "repeatable read") == 0)
+	{
+		if (doit)
+			XactIsoLevel = XACT_REPEATABLE_READ;
+	}
 	else if (strcmp(value, "read committed") == 0)
 	{
 		if (doit)
 			XactIsoLevel = XACT_READ_COMMITTED;
 	}
+	else if (strcmp(value, "read uncommitted") == 0)
+	{
+		if (doit)
+			XactIsoLevel = XACT_READ_UNCOMMITTED;
+	}
 	else if (strcmp(value, "default") == 0)
 	{
 		if (doit)
@@ -659,10 +669,19 @@ assign_XactIsoLevel(const char *value, bool doit, bool interactive)
 const char *
 show_XactIsoLevel(void)
 {
-	if (XactIsoLevel == XACT_SERIALIZABLE)
-		return "serializable";
-	else
-		return "read committed";
+	switch (XactIsoLevel)
+	{
+		case XACT_READ_UNCOMMITTED:
+			return "read uncommitted";
+		case XACT_READ_COMMITTED:
+			return "read committed";
+		case XACT_REPEATABLE_READ:
+			return "repeatable read";
+		case XACT_SERIALIZABLE:
+			return "serializable";
+		default:
+			return "bogus";
+	}
 }
 
 

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.220 2003/10/01 21:30:52 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.221 2003/11/06 22:08:14 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1139,7 +1139,7 @@ lnext:	;
 							break;
 
 						case HeapTupleUpdated:
-							if (XactIsoLevel == XACT_SERIALIZABLE)
+							if (IsXactIsoLevelSerializable)
 								ereport(ERROR,
 										(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
 										 errmsg("could not serialize access due to concurrent update")));
@@ -1440,7 +1440,7 @@ ldelete:;
 			break;
 
 		case HeapTupleUpdated:
-			if (XactIsoLevel == XACT_SERIALIZABLE)
+			if (IsXactIsoLevelSerializable)
 				ereport(ERROR,
 						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
 						 errmsg("could not serialize access due to concurrent update")));
@@ -1576,7 +1576,7 @@ lreplace:;
 			break;
 
 		case HeapTupleUpdated:
-			if (XactIsoLevel == XACT_SERIALIZABLE)
+			if (IsXactIsoLevelSerializable)
 				ereport(ERROR,
 						(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
 						 errmsg("could not serialize access due to concurrent update")));

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.436 2003/10/02 06:34:04 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.437 2003/11/06 22:08:14 petere Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -342,7 +342,7 @@ static void doNegateFloat(Value *v);
 
 	DATABASE DAY_P DEALLOCATE DEC DECIMAL_P DECLARE DEFAULT DEFAULTS
 	DEFERRABLE DEFERRED DEFINER DELETE_P DELIMITER DELIMITERS
-    DESC DISTINCT DO DOMAIN_P DOUBLE_P DROP
+	DESC DISTINCT DO DOMAIN_P DOUBLE_P DROP
 
 	EACH ELSE ENCODING ENCRYPTED END_P ESCAPE EXCEPT EXCLUDING
 	EXCLUSIVE EXECUTE EXISTS EXPLAIN EXTERNAL EXTRACT
@@ -380,7 +380,7 @@ static void doNegateFloat(Value *v);
 	PRECISION PRESERVE PREPARE PRIMARY 
 	PRIOR PRIVILEGES PROCEDURAL PROCEDURE
 
-	READ REAL RECHECK REFERENCES REINDEX RELATIVE_P RENAME REPLACE
+	READ REAL RECHECK REFERENCES REINDEX RELATIVE_P RENAME REPEATABLE REPLACE
 	RESET RESTART RESTRICT RETURNS REVOKE RIGHT ROLLBACK ROW ROWS
 	RULE
 
@@ -393,7 +393,7 @@ static void doNegateFloat(Value *v);
 	TO TOAST TRAILING TRANSACTION TREAT TRIGGER TRIM TRUE_P
 	TRUNCATE TRUSTED TYPE_P
 
-	UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNTIL
+	UNCOMMITTED UNENCRYPTED UNION UNIQUE UNKNOWN UNLISTEN UNTIL
 	UPDATE USAGE USER USING
 
 	VACUUM VALID VALIDATOR VALUES VARCHAR VARYING
@@ -922,7 +922,9 @@ var_value:	opt_boolean
 				{ $$ = makeAConst($1); }
 		;
 
-iso_level:	READ COMMITTED							{ $$ = "read committed"; }
+iso_level:	READ UNCOMMITTED						{ $$ = "read uncommitted"; }
+			| READ COMMITTED						{ $$ = "read committed"; }
+			| REPEATABLE READ						{ $$ = "repeatable read"; }
 			| SERIALIZABLE							{ $$ = "serializable"; }
 		;
 
@@ -7407,6 +7409,7 @@ unreserved_keyword:
 			| REINDEX
 			| RELATIVE_P
 			| RENAME
+			| REPEATABLE
 			| REPLACE
 			| RESET
 			| RESTART
@@ -7445,6 +7448,7 @@ unreserved_keyword:
 			| TRUNCATE
 			| TRUSTED
 			| TYPE_P
+			| UNCOMMITTED
 			| UNENCRYPTED
 			| UNKNOWN
 			| UNLISTEN

src/backend/parser/keywords.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.141 2003/08/04 02:40:01 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.142 2003/11/06 22:08:15 petere Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -251,6 +251,7 @@ static const ScanKeyword ScanKeywords[] = {
 	{"reindex", REINDEX},
 	{"relative", RELATIVE_P},
 	{"rename", RENAME},
+	{"repeatable", REPEATABLE},
 	{"replace", REPLACE},
 	{"reset", RESET},
 	{"restart", RESTART},
@@ -307,6 +308,7 @@ static const ScanKeyword ScanKeywords[] = {
 	{"truncate", TRUNCATE},
 	{"trusted", TRUSTED},
 	{"type", TYPE_P},
+	{"uncommitted", UNCOMMITTED},
 	{"unencrypted", UNENCRYPTED},
 	{"union", UNION},
 	{"unique", UNIQUE},

src/backend/utils/adt/ri_triggers.c

@@ -17,7 +17,7 @@
  *
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.63 2003/10/31 03:58:20 wieck Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.64 2003/11/06 22:08:15 petere Exp $
  *
  * ----------
  */
@@ -3073,7 +3073,7 @@ ri_PerformCheck(RI_QueryKey *qkey, void *qplan,
 	 * rows under current snapshot that wouldn't be visible per the
 	 * transaction snapshot).
 	 */
-	if (XactIsoLevel == XACT_SERIALIZABLE)
+	if (IsXactIsoLevelSerializable)
 	{
 		useCurrentSnapshot = detectNewRows;
 	}