Add support for an optional INTO clause to PL/PgSQL's EXECUTE command.

This allows the result of executing a SELECT to be assigned to a row
variable, record variable, or list of scalars. Docs and regression tests
updated. Per Pavel Stehule, improvements and cleanup by Neil Conway.

Author: Neil Conway

doc/src/sgml/plpgsql.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.69 2005/05/26 04:08:31 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.70 2005/06/07 02:47:15 neilc Exp $
 -->
 
 <chapter id="plpgsql"> 
@@ -1251,13 +1251,14 @@ NULL;
      <command>EXECUTE</command> statement is provided:
 
 <synopsis>
-EXECUTE <replaceable class="command">command-string</replaceable>;
+EXECUTE <replaceable class="command">command-string</replaceable> [ INTO <replaceable>target</replaceable> ];
 </synopsis>
 
      where <replaceable>command-string</replaceable> is an expression
-     yielding a string (of type
-     <type>text</type>) containing the command
-     to be executed.  This string is fed literally to the SQL engine.
+     yielding a string (of type <type>text</type>) containing the
+     command to be executed and <replaceable>target</replaceable> is a
+     record variable, row variable, or a comma-separated list of
+     simple variables and record/row fields.
     </para>
 
     <para>
@@ -1276,16 +1277,22 @@ EXECUTE <replaceable class="command">command-string</replaceable>;
     </para>
 
     <para>
-     The results from <command>SELECT</command> commands are discarded
-     by <command>EXECUTE</command>, and <command>SELECT INTO</command>
-     is not currently supported within <command>EXECUTE</command>.
-     So there is no way to extract a result from a dynamically-created
-     <command>SELECT</command> using the plain <command>EXECUTE</command>
-     command.  There are two other ways to do it, however: one is to use the
-     <command>FOR-IN-EXECUTE</>
-     loop form described in <xref linkend="plpgsql-records-iterating">,
-     and the other is to use a cursor with <command>OPEN-FOR-EXECUTE</>, as
-     described in <xref linkend="plpgsql-cursor-opening">.
+     The <literal>INTO</literal> clause specifies where the results of
+     a <command>SELECT</command> command should be assigned. If a row
+     or variable list is provided, it must exactly match the structure
+     of the results produced by the <command>SELECT</command> (when a
+     record variable is used, it will configure itself to match the
+     result's structure automatically). If multiple rows are returned,
+     only the first will be assigned to the <literal>INTO</literal>
+     variable. If no rows are returned, NULL is assigned to the
+     <literal>INTO</literal> variable. If no <literal>INTO</literal>
+     clause is specified, the results of a <command>SELECT</command>
+     command are discarded.
+    </para>
+
+    <para>
+     <command>SELECT INTO</command> is not currently supported within
+     <command>EXECUTE</command>.
     </para>
 
     <para>
@@ -1364,7 +1371,7 @@ EXECUTE 'UPDATE tbl SET '
      command, which has the form:
 
 <synopsis>
-GET DIAGNOSTICS <replaceable>variable</replaceable> = <replaceable>item</replaceable> <optional> , ... </optional> ;
+GET DIAGNOSTICS <replaceable>variable</replaceable> = <replaceable>item</replaceable> <optional> , ... </optional>;
 </synopsis>
 
      This command allows retrieval of system status indicators.  Each
@@ -2173,7 +2180,7 @@ SELECT merge_db (1, 'dennis');
      Another way is to use the cursor declaration syntax,
      which in general is:
 <synopsis>
-<replaceable>name</replaceable> CURSOR <optional> ( <replaceable>arguments</replaceable> ) </optional> FOR <replaceable>query</replaceable> ;
+<replaceable>name</replaceable> CURSOR <optional> ( <replaceable>arguments</replaceable> ) </optional> FOR <replaceable>query</replaceable>;
 </synopsis>
      (<literal>FOR</> may be replaced by <literal>IS</> for
      <productname>Oracle</productname> compatibility.)
@@ -2218,7 +2225,7 @@ DECLARE
      <title><command>OPEN FOR</command> <replaceable>query</replaceable></title>
 
 <synopsis>
-OPEN <replaceable>unbound_cursor</replaceable> FOR <replaceable>query</replaceable> ;
+OPEN <replaceable>unbound_cursor</replaceable> FOR <replaceable>query</replaceable>;
 </synopsis>
 
        <para>
@@ -3188,7 +3195,7 @@ DECLARE
     func_body text;
     func_cmd text;
 BEGIN 
-    func_body := 'BEGIN' ;
+    func_body := 'BEGIN';
 
     -- Notice how we scan through the results of a query in a FOR loop
     -- using the FOR &lt;record&gt; construct.

src/pl/plpgsql/src/gram.y

@@ -4,7 +4,7 @@
  *						  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.72 2005/05/26 04:08:31 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.73 2005/06/07 02:47:16 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -1250,19 +1250,62 @@ stmt_execsql	: execsql_start lno
 					}
 				;
 
-stmt_dynexecute : K_EXECUTE lno expr_until_semi
+stmt_dynexecute : K_EXECUTE lno 
 					{
 						PLpgSQL_stmt_dynexecute *new;
+						PLpgSQL_expr *expr;
+						int endtoken;
+
+						expr = read_sql_construct(K_INTO, ';', "INTO|;", "SELECT ",
+												  true, true, &endtoken);
 
 						new = palloc(sizeof(PLpgSQL_stmt_dynexecute));
 						new->cmd_type = PLPGSQL_STMT_DYNEXECUTE;
 						new->lineno   = $2;
-						new->query	  = $3;
+						new->query    = expr;
+
+						new->rec = NULL;
+						new->row = NULL;
+
+						/*
+						 * If we saw "INTO", look for an additional
+						 * row or record var.
+						 */
+						if (endtoken == K_INTO)
+						{
+							switch (yylex())
+							{
+								case T_ROW:
+									check_assignable((PLpgSQL_datum *) yylval.row);
+									new->row = yylval.row;
+									break;
+
+								case T_RECORD:
+									check_assignable((PLpgSQL_datum *) yylval.row);
+									new->rec = yylval.rec;
+									break;
+
+								case T_SCALAR:
+									new->row = read_into_scalar_list(yytext, yylval.scalar);
+									break;
+
+								default:
+									plpgsql_error_lineno = $2;
+									ereport(ERROR,
+											(errcode(ERRCODE_SYNTAX_ERROR),
+											 errmsg("syntax error at \"%s\"",
+													yytext),
+											 errdetail("Expected record or row variable.")));
+							}
+							if (yylex() != ';')
+								yyerror("syntax error");
+						}
 
 						$$ = (PLpgSQL_stmt *)new;
 					}
 				;
 
+
 stmt_open		: K_OPEN lno cursor_varptr
 					{
 						PLpgSQL_stmt_open *new;

src/pl/plpgsql/src/pl_exec.c

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.141 2005/05/26 04:08:31 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.142 2005/06/07 02:47:17 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -2202,6 +2202,13 @@ exec_stmt_dynexecute(PLpgSQL_execstate *estate,
 	Oid			restype;
 	char	   *querystr;
 	int			exec_res;
+	PLpgSQL_rec *rec = NULL;
+	PLpgSQL_row *row = NULL;
+
+	if (stmt->rec != NULL)
+		rec = (PLpgSQL_rec *) (estate->datums[stmt->rec->recno]);
+	else if (stmt->row != NULL)
+		row = (PLpgSQL_row *) (estate->datums[stmt->row->rowno]);
 
 	/*
 	 * First we evaluate the string expression after the EXECUTE keyword.
@@ -2221,9 +2228,27 @@ exec_stmt_dynexecute(PLpgSQL_execstate *estate,
 	/*
 	 * Call SPI_execute() without preparing a saved plan. The returncode can
 	 * be any standard OK.	Note that while a SELECT is allowed, its
-	 * results will be discarded.
+	 * results will be discarded unless an INTO clause is specified.
 	 */
 	exec_res = SPI_execute(querystr, estate->readonly_func, 0);
+
+	/* Assign to INTO variable */
+	if (rec || row)
+	{
+		if (exec_res != SPI_OK_SELECT)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("EXECUTE ... INTO is only for SELECT")));
+		else
+		{
+			if (SPI_processed == 0)
+				exec_move_row(estate, rec, row, NULL, SPI_tuptable->tupdesc);
+			else
+				exec_move_row(estate, rec, row,
+							  SPI_tuptable->vals[0], SPI_tuptable->tupdesc);
+		}
+	}
+
 	switch (exec_res)
 	{
 		case SPI_OK_SELECT:

src/pl/plpgsql/src/plpgsql.h

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.60 2005/05/26 04:08:31 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.61 2005/06/07 02:47:18 neilc Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -524,6 +524,8 @@ typedef struct
 {								/* Dynamic SQL string to execute */
 	int			cmd_type;
 	int			lineno;
+	PLpgSQL_rec *rec;					/* INTO record or row variable */
+	PLpgSQL_row *row;
 	PLpgSQL_expr *query;
 } PLpgSQL_stmt_dynexecute;
 

src/test/regress/expected/plpgsql.out

@@ -2380,3 +2380,38 @@ ERROR:  control reached end of function without RETURN
 CONTEXT:  PL/pgSQL function "missing_return_expr"
 drop function void_return_expr();
 drop function missing_return_expr();
+--
+-- EXECUTE ... INTO test
+--
+create table eifoo (i integer, y integer);
+create type eitype as (i integer, y integer);
+create or replace function execute_into_test(varchar) returns record as $$
+declare
+    _r record;
+    _rt eifoo%rowtype;
+    _v eitype;
+    i int;
+    j int;
+    k int;
+begin
+    execute 'insert into '||$1||' values(10,15)';
+    execute 'select (row).* from (select row(10,1)::eifoo) s' into _r;
+    raise notice '% %', _r.i, _r.y;
+    execute 'select * from '||$1||' limit 1' into _rt;
+    raise notice '% %', _rt.i, _rt.y;
+    execute 'select *, 20 from '||$1||' limit 1' into i, j, k;
+    raise notice '% % %', i, j, k;
+    execute 'select 1,2' into _v;
+    return _v;
+end; $$ language plpgsql;
+select execute_into_test('eifoo');
+NOTICE:  10 1
+NOTICE:  10 15
+NOTICE:  10 15 20
+ execute_into_test 
+-------------------
+ (1,2)
+(1 row)
+
+drop table eifoo cascade;
+drop type eitype cascade;

src/test/regress/sql/plpgsql.sql

@@ -2018,3 +2018,35 @@ select missing_return_expr();
 
 drop function void_return_expr();
 drop function missing_return_expr();
+
+--
+-- EXECUTE ... INTO test
+--
+
+create table eifoo (i integer, y integer);
+create type eitype as (i integer, y integer);
+
+create or replace function execute_into_test(varchar) returns record as $$
+declare
+    _r record;
+    _rt eifoo%rowtype;
+    _v eitype;
+    i int;
+    j int;
+    k int;
+begin
+    execute 'insert into '||$1||' values(10,15)';
+    execute 'select (row).* from (select row(10,1)::eifoo) s' into _r;
+    raise notice '% %', _r.i, _r.y;
+    execute 'select * from '||$1||' limit 1' into _rt;
+    raise notice '% %', _rt.i, _rt.y;
+    execute 'select *, 20 from '||$1||' limit 1' into i, j, k;
+    raise notice '% % %', i, j, k;
+    execute 'select 1,2' into _v;
+    return _v;
+end; $$ language plpgsql;
+
+select execute_into_test('eifoo');
+
+drop table eifoo cascade;
+drop type eitype cascade;