Add trivial NULL statement to plpgsql, for Oracle compatibility.

diff --git a/doc/src/sgml/plpgsql.sgml b/doc/src/sgml/plpgsql.sgml
index 5e21d1abb68e8ad18c58398d883372b4add1889d..ff2b4b2a74958f285d106c481b2d2a29fcd60472 100644 (file)
--- a/doc/src/sgml/plpgsql.sgml
+++ b/doc/src/sgml/plpgsql.sgml
@@ -1,5 +1,5 @@
 
 
  
@@ -1098,6 +1098,52 @@ PERFORM create_mv('cs_session_page_requests_mv', my_query);
     
    
 
+   
+    Doing Nothing At All
+
+    
+     Sometimes a placeholder statement that does nothing is useful.
+     For example, it can indicate that one arm of an if/then/else
+     chain is deliberately empty.  For this purpose, use the
+     NULL statement:
+
+
+NULL;
+
+    
+
+    
+     For example, the following two fragments of code are equivalent:
+
+    BEGIN
+        y := x / 0;
+    EXCEPTION
+        WHEN division_by_zero THEN
+            NULL;  -- ignore the error
+    END;
+
+
+
+    BEGIN
+        y := x / 0;
+    EXCEPTION
+        WHEN division_by_zero THEN  -- ignore the error
+    END;
+
+     Which is preferable is a matter of taste.
+    
+
+    
+     
+      In Oracle's PL/SQL, empty statement lists are not allowed, and so
+      NULL statements are required for situations
+      such as this.  PL/pgSQL allows you to
+      just write nothing, instead.
+     
+    
+
+   
+
    
     Executing Dynamic Commands
 
@@ -1129,7 +1175,7 @@ EXECUTE command-string;
     
     When working with dynamic commands you will often have to handle escaping
     of single quotes.  The recommended method for quoting fixed text in your
-    function body is dollar quoting.  If you have legacy code which does
+    function body is dollar quoting.  If you have legacy code that does
     not use dollar quoting, please refer to the
     overview in , which can save you
     some effort when translating said code to a more reasonable scheme.
@@ -1158,14 +1204,15 @@ EXECUTE command-string;
     
 
     
-     An example (this assumes that you are using dollar quoting, so the
-     quote marks need not be doubled):
+     An example (this assumes that you are using dollar quoting for the
+     function as a whole, so the quote marks need not be doubled):
 
 EXECUTE 'UPDATE tbl SET '
         || quote_ident(colname)
         || ' = '
         || quote_literal(newvalue)
-        || ' WHERE ...';
+        || ' WHERE key = '
+        || quote_literal(keyvalue);
 
     
 
@@ -1193,7 +1240,8 @@ EXECUTE 'UPDATE tbl SET '
         || quote_ident(colname)
         || ' = $$'
         || newvalue
-        || '$$ WHERE ...';
+        || '$$ WHERE key = '
+        || quote_literal(keyvalue);
 
      because it would break if the contents of newvalue
      happened to contain $$.  The same objection would

diff --git a/src/pl/plpgsql/src/gram.y b/src/pl/plpgsql/src/gram.y
index 96c5c61725dcdad56537f577d5c68f6b7dd3270f..c5c6ddf703ccfcc8c298284d7e87a2b6d5a2b23f 100644 (file)
--- a/src/pl/plpgsql/src/gram.y
+++ b/src/pl/plpgsql/src/gram.y
@@ -4,7 +4,7 @@
  *                       procedural language
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.59 2004/07/31 23:04:56 tgl Exp $
+ *   $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.60 2004/08/16 17:52:06 tgl Exp $
  *
  *   This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -132,7 +132,7 @@ static  void check_assignable(PLpgSQL_datum *datum);
 %type    stmt_return stmt_return_next stmt_raise stmt_execsql
 %type    stmt_for stmt_select stmt_perform
 %type    stmt_dynexecute stmt_getdiag
-%type    stmt_open stmt_fetch stmt_close
+%type    stmt_open stmt_fetch stmt_close stmt_null
 
 %type  exception_sect proc_exceptions
 %type   proc_exception
@@ -592,29 +592,31 @@ proc_sect     :
 
 proc_stmts     : proc_stmts proc_stmt
                        {
+                           if ($2 != NULL)
+                           {
                                if ($1->stmts_used == $1->stmts_alloc)
                                {
                                    $1->stmts_alloc *= 2;
                                    $1->stmts = realloc($1->stmts, sizeof(PLpgSQL_stmt *) * $1->stmts_alloc);
                                }
                                $1->stmts[$1->stmts_used++] = $2;
-
-                               $$ = $1;
+                           }
+                           $$ = $1;
                        }
                | proc_stmt
                        {
-                               PLpgSQL_stmts   *new;
+                           PLpgSQL_stmts   *new;
 
-                               new = malloc(sizeof(PLpgSQL_stmts));
-                               memset(new, 0, sizeof(PLpgSQL_stmts));
+                           new = malloc(sizeof(PLpgSQL_stmts));
+                           memset(new, 0, sizeof(PLpgSQL_stmts));
 
-                               new->stmts_alloc = 64;
-                               new->stmts_used  = 1;
-                               new->stmts = malloc(sizeof(PLpgSQL_stmt *) * new->stmts_alloc);
-                               new->stmts[0] = $1;
+                           new->stmts_alloc = 32;
+                           new->stmts = malloc(sizeof(PLpgSQL_stmt *) * new->stmts_alloc);
 
-                               $$ = new;
+                           if ($1 != NULL)
+                               new->stmts[new->stmts_used++] = $1;
 
+                           $$ = new;
                        }
                ;
 
@@ -654,6 +656,8 @@ proc_stmt       : pl_block ';'
                        { $$ = $1; }
                | stmt_close
                        { $$ = $1; }
+               | stmt_null
+                       { $$ = $1; }
                ;
 
 stmt_perform   : K_PERFORM lno expr_until_semi
@@ -1493,6 +1497,13 @@ stmt_close       : K_CLOSE lno cursor_variable ';'
                    }
                ;
 
+stmt_null      : K_NULL ';'
+                   {
+                       /* We do not bother building a node for NULL */
+                       $$ = NULL;
+                   }
+               ;
+
 cursor_varptr  : T_SCALAR
                    {
                        if (yylval.scalar->dtype != PLPGSQL_DTYPE_VAR)