Allow commas in BEGIN, START TRANSACTION, and SET TRANSACTION, as required

by the SQL standard.  For backwards compatibility, however, continue to
accept the syntax without.  Minor editorialization in the reference pages
for these commands, too.

doc/src/sgml/ref/begin.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/begin.sgml,v 1.32 2004/08/08 01:48:31 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/begin.sgml,v 1.33 2004/08/12 21:00:21 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -20,9 +20,12 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-BEGIN [ WORK | TRANSACTION ]
-    [ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
-    [ READ WRITE | READ ONLY ]
+BEGIN [ WORK | TRANSACTION ] [ <replaceable class="parameter">transaction_mode</replaceable> [, ...] ]
+
+where <replaceable class="parameter">transaction_mode</replaceable> is one of:
+
+    ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }
+    READ WRITE | READ ONLY
 </synopsis>
  </refsynopsisdiv>
  
@@ -101,8 +104,13 @@ BEGIN [ WORK | TRANSACTION ]
    Issuing <command>BEGIN</> when already inside a transaction block will
    provoke a warning message.  The state of the transaction is not affected.
    To nest transactions within a transaction block, use savepoints 
-   (See <xref linkend="sql-start-transaction" endterm="sql-start-transaction-title">
-   for more information).
+   (see <xref linkend="sql-savepoint" endterm="sql-savepoint-title">).
+  </para>
+
+  <para>
+   For reasons of backwards compatibility, the commas between successive
+   <replaceable class="parameter">transaction_modes</replaceable> may be
+   omitted.
   </para>
  </refsect1>
 
@@ -123,15 +131,10 @@ BEGIN;
 
   <para>
    <command>BEGIN</command> is a <productname>PostgreSQL</productname>
-   language extension.  There is no explicit <command>BEGIN</command>
-   command in the SQL standard; transaction initiation is
-   always implicit and it terminates either with a
-   <command>COMMIT</command> or <command>ROLLBACK</command> statement.
-  </para>
-
-  <para>
-   Other relational database systems may offer an autocommit feature
-   as a convenience.
+   language extension.  It is equivalent to the SQL-standard command
+   <xref linkend="sql-start-transaction"
+   endterm="sql-start-transaction-title">, which see for additional
+   compatibility information.
   </para>
 
   <para>

doc/src/sgml/ref/set_transaction.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.19 2003/11/29 19:51:39 pgsql Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_transaction.sgml,v 1.20 2004/08/12 21:00:22 tgl Exp $ -->
 <refentry id="SQL-SET-TRANSACTION">
  <refmeta>
   <refentrytitle id="SQL-SET-TRANSACTION-TITLE">SET TRANSACTION</refentrytitle>
@@ -16,13 +16,13 @@
 
  <refsynopsisdiv>
 <synopsis>
-SET TRANSACTION
-    [ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
-    [ READ WRITE | READ ONLY ]
+SET TRANSACTION <replaceable class="parameter">transaction_mode</replaceable> [, ...]
+SET SESSION CHARACTERISTICS AS TRANSACTION <replaceable class="parameter">transaction_mode</replaceable> [, ...]
 
-SET SESSION CHARACTERISTICS AS TRANSACTION
-    [ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
-    [ READ WRITE | READ ONLY ]
+where <replaceable class="parameter">transaction_mode</replaceable> is one of:
+
+    ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }
+    READ WRITE | READ ONLY
 </synopsis>
  </refsynopsisdiv>
 
@@ -34,7 +34,7 @@ SET SESSION CHARACTERISTICS AS TRANSACTION
    characteristics of the current 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
+   characteristics for subsequent transactions of a session.  <command>SET
    TRANSACTION</command> can override it for an individual
    transaction.
   </para>
@@ -47,7 +47,7 @@ SET SESSION CHARACTERISTICS AS TRANSACTION
 
   <para>
    The isolation level of a transaction determines what data the
-   transaction can see when other transactions are running concurrently.
+   transaction can see when other transactions are running concurrently:
 
    <variablelist>
     <varlistentry>
@@ -64,28 +64,35 @@ SET SESSION CHARACTERISTICS AS TRANSACTION
      <term><literal>SERIALIZABLE</literal></term>
      <listitem>
       <para>
-       The current transaction can only see rows committed before
-       first query or data-modification statement was executed in this transaction.
+       All statements of the current transaction can only see rows committed
+       before the first query or data-modification statement was executed in
+       this transaction.
       </para>
       <tip>
        <para>
         Intuitively, serializable means that two concurrent
         transactions will leave the database in the same state as if
-        the two has been executed strictly after one another in either
-        order.
+        the two had been executed strictly one after the other (in one
+        order or the other).
        </para>
       </tip>
      </listitem>
     </varlistentry>
    </variablelist>
 
-   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
+   The SQL standard defines two additional levels, <literal>READ
+   UNCOMMITTED</literal> and <literal>REPEATABLE READ</literal>.
+   In <productname>PostgreSQL</productname> <literal>READ
+   UNCOMMITTED</literal> is treated as
+   <literal>READ COMMITTED</literal>, while <literal>REPEATABLE
+   READ</literal> is treated as <literal>SERIALIZABLE</literal>.
+  </para>
+
+  <para>
+   The transaction isolation level cannot be changed after the first query or
    data-modification statement (<command>SELECT</command>,
    <command>INSERT</command>, <command>DELETE</command>,
-   <command>UPDATE</command>, <command>FETCH</command>,
+   <command>UPDATE</command>, <command>FETCH</command>, or
    <command>COPY</command>) of a transaction has been executed.  See
    <xref linkend="mvcc"> for more information about transaction
    isolation and concurrency control.
@@ -112,13 +119,27 @@ SET SESSION CHARACTERISTICS AS TRANSACTION
   <title>Notes</title>
 
   <para>
-   The session default transaction isolation level can also be set
-   with the command
-<programlisting>
-SET default_transaction_isolation = '<replaceable>value</replaceable>'
-</programlisting>
-   and in the configuration file.  Consult <xref linkend="runtime-config"> for more
-   information.
+   If <command>SET TRANSACTION</command> is executed without a prior
+   <command>START TRANSACTION</command> or  <command>BEGIN</command>,
+   it will appear to have no effect, since the transaction will immediately
+   end.
+  </para>
+
+  <para>
+   It is possible to dispense with <command>SET TRANSACTION</command> by
+   instead specifying the desired <replaceable
+   class="parameter">transaction_modes</replaceable> in
+   <command>START TRANSACTION</command>.
+  </para>
+
+  <para>
+   The session default transaction modes can also be set by setting the
+   configuration parameters <xref linkend="guc-default-transaction-isolation">
+   and <xref linkend="guc-default-transaction-read-only">.
+   (In fact <command>SET SESSION CHARACTERISTICS</command> is just a
+   verbose equivalent for setting these variables with <command>SET</>.)
+   This allows them to be set in the configuration file.  Consult <xref
+   linkend="runtime-config"> for more information.
   </para>
  </refsect1>
 
@@ -131,7 +152,7 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
    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
+   mentioned above.  Because of multiversion concurrency control, the
    <literal>SERIALIZABLE</literal> level is not truly
    serializable. See <xref linkend="mvcc"> for details.
   </para>
@@ -139,7 +160,15 @@ SET default_transaction_isolation = '<replaceable>value</replaceable>'
   <para>
    In the SQL standard, there is one other transaction characteristic
    that can be set with these commands: the size of the diagnostics
-   area.  This concept is only for use in embedded SQL.
+   area.  This concept is specific to embedded SQL, and therefore is
+   not implemented in the <productname>PostgreSQL</productname> server.
+  </para>
+
+  <para>
+   The SQL standard requires commas between successive <replaceable
+   class="parameter">transaction_modes</replaceable>, but for historical
+   reasons <productname>PostgreSQL</productname> allows the commas to be
+   omitted.
   </para>
  </refsect1>
 </refentry>

doc/src/sgml/ref/start_transaction.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.12 2004/08/01 17:32:13 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/start_transaction.sgml,v 1.13 2004/08/12 21:00:23 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -20,9 +20,12 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-START TRANSACTION
-    [ ISOLATION LEVEL { READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE } ]
-    [ READ WRITE | READ ONLY ]
+START TRANSACTION [ <replaceable class="parameter">transaction_mode</replaceable> [, ...] ]
+
+where <replaceable class="parameter">transaction_mode</replaceable> is one of:
+
+    ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }
+    READ WRITE | READ ONLY
 </synopsis>
  </refsynopsisdiv>
 
@@ -30,10 +33,10 @@ START TRANSACTION
   <title>Description</title>
 
   <para>
-   This command begins a new transaction. If the isolation level or
+   This command begins a new transaction block. 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. It is the same
+   endterm="sql-set-transaction-title"> was executed. This is the same
    as the <xref linkend="sql-begin" endterm="sql-begin-title"> command.
   </para>
  </refsect1>
@@ -52,8 +55,25 @@ START TRANSACTION
   <title>Compatibility</title>
 
   <para>
-   This command conforms to the SQL standard; but see also the
-   compatibility section of <xref linkend="sql-set-transaction"
+   In the standard, it is not necessary to issue <command>START TRANSACTION</>
+   to start a transaction block: any SQL command implicitly begins a block.
+   <productname>PostgreSQL</productname>'s behavior can be seen as implicitly
+   issuing a <command>COMMIT</command> after each command that does not
+   follow <command>START TRANSACTION</> (or <command>BEGIN</command>),
+   and it is therefore often called <quote>autocommit</>.
+   Other relational database systems may offer an autocommit feature
+   as a convenience.
+  </para>
+
+  <para>
+   The SQL standard requires commas between successive <replaceable
+   class="parameter">transaction_modes</replaceable>, but for historical
+   reasons <productname>PostgreSQL</productname> allows the commas to be
+   omitted.
+  </para>
+
+  <para>
+   See also the compatibility section of <xref linkend="sql-set-transaction"
    endterm="sql-set-transaction-title">.
   </para>
  </refsect1>

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.470 2004/08/12 19:12:21 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.471 2004/08/12 21:00:28 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -161,11 +161,11 @@ static void doNegateFloat(Value *v);
 
 %type <dbehavior>	opt_drop_behavior
 
-%type <list>	createdb_opt_list copy_opt_list
-%type <defelt>	createdb_opt_item copy_opt_item
+%type <list>	createdb_opt_list copy_opt_list transaction_mode_list
+%type <defelt>	createdb_opt_item copy_opt_item transaction_mode_item
 
 %type <ival>	opt_lock lock_type cast_context
-%type <boolean>	opt_force opt_or_replace transaction_access_mode
+%type <boolean>	opt_force opt_or_replace
 				opt_grant_grant_option opt_revoke_grant_option
 				opt_nowait
 
@@ -222,7 +222,7 @@ static void doNegateFloat(Value *v);
 				target_list update_target_list insert_column_list
 				insert_target_list def_list indirection opt_indirection
 				group_clause TriggerFuncArgs select_limit
-				opt_select_limit opclass_item_list transaction_mode_list
+				opt_select_limit opclass_item_list
 				transaction_mode_list_or_empty
 				TableFuncElementList
 				prep_type_clause prep_type_list
@@ -4021,27 +4021,26 @@ opt_transaction:	WORK							{}
 			| /*EMPTY*/								{}
 		;
 
-transaction_mode_list:
+transaction_mode_item:
 			ISOLATION LEVEL iso_level
-					{ $$ = list_make1(makeDefElem("transaction_isolation",
-												  makeStringConst($3, NULL))); }
-			| transaction_access_mode
-					{ $$ = list_make1(makeDefElem("transaction_read_only",
-												  makeIntConst($1))); }
-			| ISOLATION LEVEL iso_level transaction_access_mode
-					{
-						$$ = list_make2(makeDefElem("transaction_isolation",
-													makeStringConst($3, NULL)),
-										makeDefElem("transaction_read_only",
-													makeIntConst($4)));
-					}
-			| transaction_access_mode ISOLATION LEVEL iso_level
-					{
-						$$ = list_make2(makeDefElem("transaction_read_only",
-													makeIntConst($1)),
-										makeDefElem("transaction_isolation",
-													makeStringConst($4, NULL)));
-					}
+					{ $$ = makeDefElem("transaction_isolation",
+									   makeStringConst($3, NULL)); }
+			| READ ONLY
+					{ $$ = makeDefElem("transaction_read_only",
+									   makeIntConst(TRUE)); }
+			| READ WRITE
+					{ $$ = makeDefElem("transaction_read_only",
+									   makeIntConst(FALSE)); }
+		;
+
+/* Syntax with commas is SQL-spec, without commas is Postgres historical */
+transaction_mode_list:
+			transaction_mode_item
+					{ $$ = list_make1($1); }
+			| transaction_mode_list ',' transaction_mode_item
+					{ $$ = lappend($1, $3); }
+			| transaction_mode_list transaction_mode_item
+					{ $$ = lappend($1, $2); }
 		;
 
 transaction_mode_list_or_empty:
@@ -4050,11 +4049,6 @@ transaction_mode_list_or_empty:
 					{ $$ = NIL; }
 		;
 
-transaction_access_mode:
-			READ ONLY { $$ = TRUE; }
-			| READ WRITE { $$ = FALSE; }
-		;
-
 
 /*****************************************************************************
  *

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.224 2004/08/12 19:12:21 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.225 2004/08/12 21:00:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -333,23 +333,21 @@ ProcessUtility(Node *parsetree,
 					case TRANS_STMT_BEGIN:
 					case TRANS_STMT_START:
 						{
-							BeginTransactionBlock();
+							ListCell   *lc;
 
-							if (stmt->options)
+							BeginTransactionBlock();
+							foreach(lc, stmt->options)
 							{
-								ListCell   *head;
-
-								foreach(head, stmt->options)
-								{
-									DefElem    *item = (DefElem *) lfirst(head);
+								DefElem    *item = (DefElem *) lfirst(lc);
 
 								if (strcmp(item->defname, "transaction_isolation") == 0)
 									SetPGVariable("transaction_isolation",
-											list_make1(item->arg), false);
+												  list_make1(item->arg),
+												  false);
 								else if (strcmp(item->defname, "transaction_read_only") == 0)
 									SetPGVariable("transaction_read_only",
-											list_make1(item->arg), false);
-								}
+												  list_make1(item->arg),
+												  false);
 							}
 						}
 						break;