Allow PL/pgSQL FOR statement to return values to scalars as well as

records and row types.

Pavel Stehule

Author: bmomjian

doc/src/sgml/plpgsql.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.84 2006/02/05 02:47:53 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.85 2006/02/12 06:03:38 momjian Exp $
 -->
 
 <chapter id="plpgsql"> 
@@ -2008,11 +2008,13 @@ END LOOP;
      accordingly. The syntax is:
 <synopsis>
 <optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
-FOR <replaceable>record_or_row</replaceable> IN <replaceable>query</replaceable> LOOP
+FOR <replaceable>target</replaceable> IN <replaceable>query</replaceable> LOOP
     <replaceable>statements</replaceable>
 END LOOP <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>
-     The record or row variable is successively assigned each row
+     <replaceable>Target</replaceable> is a record variable, row variable, 
+     or a comma-separated list of  simple variables and record/row fields
+     which is successively assigned each row
      resulting from the <replaceable>query</replaceable> (which must be a
      <command>SELECT</command> command) and the loop body is executed for each
      row. Here is an example:
@@ -2047,7 +2049,7 @@ $$ LANGUAGE plpgsql;
      rows:
 <synopsis>
 <optional> &lt;&lt;<replaceable>label</replaceable>&gt;&gt; </optional>
-FOR <replaceable>record_or_row</replaceable> IN EXECUTE <replaceable>text_expression</replaceable> LOOP 
+FOR <replaceable>target</replaceable> IN EXECUTE <replaceable>text_expression</replaceable> LOOP 
     <replaceable>statements</replaceable>
 END LOOP <optional> <replaceable>label</replaceable> </optional>;
 </synopsis>
@@ -2067,7 +2069,7 @@ END LOOP <optional> <replaceable>label</replaceable> </optional>;
      <literal>IN</> and <literal>LOOP</>.  If <literal>..</> is not seen then
      the loop is presumed to be a loop over rows.  Mistyping the <literal>..</>
      is thus likely to lead to a complaint along the lines of
-     <quote>loop variable of loop over rows must be a record or row variable</>,
+     <quote>loop variable of loop over rows must be a record or row or scalar variable</>,
      rather than the simple syntax error one might expect to get.
     </para>
     </note>

src/pl/plpgsql/src/gram.y

@@ -4,7 +4,7 @@
  *						  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.83 2006/02/12 04:59:32 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.84 2006/02/12 06:03:38 momjian Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -58,7 +58,9 @@ static	void			 check_sql_expr(const char *stmt);
 static	void			 plpgsql_sql_error_callback(void *arg);
 static	void			 check_labels(const char *start_label,
 									  const char *end_label);
-
+static PLpgSQL_row       *make_scalar_list1(const char *name,
+					    PLpgSQL_datum *variable);
+ 
 %}
 
 %union {
@@ -76,6 +78,7 @@ static	void			 check_labels(const char *start_label,
 			int  lineno;
 			PLpgSQL_rec     *rec;
 			PLpgSQL_row     *row;
+		        PLpgSQL_datum   *scalar;
 		}						forvariable;
 		struct
 		{
@@ -890,10 +893,15 @@ for_control		:
 								new->row = $2.row;
 								check_assignable((PLpgSQL_datum *) new->row);
 							}
+							else if ($2.scalar)
+							{
+						        new->row = make_scalar_list1($2.name, $2.scalar);
+								check_assignable((PLpgSQL_datum *) new->row);
+							}
 							else
 							{
 								plpgsql_error_lineno = $1;
-								yyerror("loop variable of loop over rows must be a record or row variable");
+								yyerror("loop variable of loop over rows must be a record, row, or scalar variable");
 							}
 							new->query = expr;
 
@@ -948,6 +956,15 @@ for_control		:
 
 								expr2 = plpgsql_read_expression(K_LOOP, "LOOP");
 
+								/* T_SCALAR identifier waits for converting */
+								if ($2.scalar)
+								{
+								    char *name;
+								    plpgsql_convert_ident($2.name, &name, 1);
+								    pfree($2.name);
+								    $2.name = name;
+								}
+
 								/* create loop's private variable */
 								fvar = (PLpgSQL_var *)
 									plpgsql_build_variable($2.name,
@@ -1002,10 +1019,15 @@ for_control		:
 									new->row = $2.row;
 									check_assignable((PLpgSQL_datum *) new->row);
 								}
+								else if ($2.scalar)
+								{
+							        new->row = make_scalar_list1($2.name, $2.scalar);
+									check_assignable((PLpgSQL_datum *) new->row);
+								}
 								else
 								{
 									plpgsql_error_lineno = $1;
-									yyerror("loop variable of loop over rows must be record or row variable");
+									yyerror("loop variable of loop over rows must be record, row, or scalar variable");
 								}
 
 								new->query = expr1;
@@ -1027,14 +1049,31 @@ for_control		:
  * until we know what's what.
  */
 for_variable	: T_SCALAR
-					{
+  					{
+						int tok;
 						char		*name;
+						
+						name = pstrdup(yytext);
+						$$.scalar = yylval.scalar;
+						$$.lineno = plpgsql_scanner_lineno();
 
-						plpgsql_convert_ident(yytext, &name, 1);
-						$$.name = name;
-						$$.lineno  = plpgsql_scanner_lineno();
-						$$.rec = NULL;
-						$$.row = NULL;
+						if((tok = yylex()) == ',')
+						{
+						    plpgsql_push_back_token(tok);
+						    $$.name = NULL;
+						    $$.row = read_into_scalar_list(name, $$.scalar);
+						    $$.rec = NULL;
+						    $$.scalar = NULL;
+						    
+						    pfree(name);
+						}
+						else
+						{
+						    plpgsql_push_back_token(tok);
+						    $$.name = name;
+						    $$.row = NULL;
+						    $$.rec = NULL;
+						}
 					}
 				| T_WORD
 					{
@@ -1048,20 +1087,14 @@ for_variable	: T_SCALAR
 					}
 				| T_RECORD
 					{
-						char		*name;
-
-						plpgsql_convert_ident(yytext, &name, 1);
-						$$.name = name;
+						$$.name = NULL;
 						$$.lineno  = plpgsql_scanner_lineno();
 						$$.rec = yylval.rec;
 						$$.row = NULL;
 					}
 				| T_ROW
 					{
-						char		*name;
-
-						plpgsql_convert_ident(yytext, &name, 1);
-						$$.name = name;
+					        $$.name = NULL;
 						$$.lineno  = plpgsql_scanner_lineno();
 						$$.row = yylval.row;
 						$$.rec = NULL;
@@ -2088,6 +2121,30 @@ make_fetch_stmt(void)
 }
 
 
+static PLpgSQL_row *
+make_scalar_list1(const char *name,
+ 				  PLpgSQL_datum *variable)
+{
+ 	PLpgSQL_row		*row;
+ 	check_assignable(variable);
+ 	
+ 	row = palloc(sizeof(PLpgSQL_row));
+ 	row->dtype = PLPGSQL_DTYPE_ROW;
+ 	row->refname = pstrdup("*internal*");
+ 	row->lineno = plpgsql_scanner_lineno();
+ 	row->rowtupdesc = NULL;
+ 	row->nfields = 1;
+ 	row->fieldnames = palloc(sizeof(char *) * 1);
+ 	row->varnos = palloc(sizeof(int) * 1);
+ 	row->fieldnames[0] = pstrdup(name);
+ 	row->varnos[0] = variable->dno;
+ 
+ 	plpgsql_adddatum((PLpgSQL_datum *)row);
+ 
+ 	return row;
+} 
+
+
 static void
 check_assignable(PLpgSQL_datum *datum)
 {

src/test/regress/expected/plpgsql.out

@@ -2721,3 +2721,23 @@ end;
 $$ language plpgsql;
 ERROR:  end label "outer_label" specified for unlabelled block
 CONTEXT:  compile of PL/pgSQL function "end_label4" near line 5
+-- using list of scalars in fori and fore stmts
+create function for_vect() returns void as $$
+<<lbl>>declare a integer; b varchar; c varchar; r record;
+begin
+  -- old fori
+  for i in 1 .. 10 loop
+    raise notice '%', i;
+  end loop;
+  for a in select 1 from generate_series(1,4) loop
+    raise notice '%', a;
+  end loop;
+  for a,b,c in select generate_series, 'BB','CC' from generate_series(1,4) loop
+    raise notice '% % %', a, b, c;
+  end loop;
+  -- using qualified names in fors, fore is enabled, disabled only for fori
+  for lbl.a, lbl.b, lbl.c in execute E'select generate_series, \'bb\',\'cc\' from generate_series(1,4)' loop
+    raise notice '% % %', a, b, c;
+  end loop;
+end;
+$$ language plpgsql;

src/test/regress/sql/plpgsql.sql

@@ -2280,3 +2280,25 @@ begin
   end loop outer_label;
 end;
 $$ language plpgsql;
+
+
+-- using list of scalars in fori and fore stmts
+create function for_vect() returns void as $$
+<<lbl>>declare a integer; b varchar; c varchar; r record;
+begin
+  -- old fori
+  for i in 1 .. 10 loop
+    raise notice '%', i;
+  end loop;
+  for a in select 1 from generate_series(1,4) loop
+    raise notice '%', a;
+  end loop;
+  for a,b,c in select generate_series, 'BB','CC' from generate_series(1,4) loop
+    raise notice '% % %', a, b, c;
+  end loop;
+  -- using qualified names in fors, fore is enabled, disabled only for fori
+  for lbl.a, lbl.b, lbl.c in execute E'select generate_series, \'bb\',\'cc\' from generate_series(1,4)' loop
+    raise notice '% % %', a, b, c;
+  end loop;
+end;
+$$ language plpgsql;