plpgsql can assign to subscripted variables now, e.g.

x[42] := whatever;
The facility is pretty primitive because it doesn't do array slicing and
it has the same semantics as array update in SQL (array must already
be non-null, etc).  But it's a start.

src/pl/plpgsql/src/gram.y

@@ -4,7 +4,7 @@
  *						  procedural language
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/gram.y,v 1.40 2002/11/10 00:35:58 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/gram.y,v 1.41 2003/03/25 03:16:40 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -105,7 +105,8 @@ static	void check_assignable(PLpgSQL_datum *datum);
 %type <nsitem>	decl_aliasitem
 %type <str>		decl_stmts decl_stmt
 
-%type <expr>	expr_until_semi expr_until_then expr_until_loop
+%type <expr>	expr_until_semi expr_until_rightbracket
+%type <expr>	expr_until_then expr_until_loop
 %type <expr>	opt_exitcond
 
 %type <ival>	assign_var cursor_variable
@@ -822,6 +823,21 @@ assign_var		: T_VARIABLE
 						check_assignable(yylval.variable);
 						$$ = yylval.variable->dno;
 					}
+				| assign_var '[' expr_until_rightbracket
+					{
+						PLpgSQL_arrayelem	*new;
+
+						new = malloc(sizeof(PLpgSQL_arrayelem));
+						memset(new, 0, sizeof(PLpgSQL_arrayelem));
+
+						new->dtype		= PLPGSQL_DTYPE_ARRAYELEM;
+						new->subscript	= $3;
+						new->arrayparentno = $1;
+
+						plpgsql_adddatum((PLpgSQL_datum *)new);
+
+						$$ = new->dno;
+					}
 				;
 
 stmt_if			: K_IF lno expr_until_then proc_sect stmt_else K_END K_IF ';'
@@ -1491,6 +1507,10 @@ expr_until_semi :
 					{ $$ = plpgsql_read_expression(';', ";"); }
 				;
 
+expr_until_rightbracket :
+					{ $$ = plpgsql_read_expression(']', "]"); }
+				;
+
 expr_until_then :
 					{ $$ = plpgsql_read_expression(K_THEN, "THEN"); }
 				;
@@ -1577,16 +1597,16 @@ read_sql_construct(int until,
 	for (;;)
 	{
 		tok = yylex();
-		if (tok == '(')
+		if (tok == until && parenlevel == 0)
+			break;
+		if (tok == '(' || tok == '[')
 			parenlevel++;
-		else if (tok == ')')
+		else if (tok == ')' || tok == ']')
 		{
 			parenlevel--;
 			if (parenlevel < 0)
 				elog(ERROR, "mismatched parentheses");
 		}
-		else if (parenlevel == 0 && tok == until)
-			break;
 		/*
 		 * End of function definition is an error, and we don't expect to
 		 * hit a semicolon either (unless it's the until symbol, in which
@@ -1988,6 +2008,9 @@ check_assignable(PLpgSQL_datum *datum)
 		case PLPGSQL_DTYPE_RECFIELD:
 			/* always assignable? */
 			break;
+		case PLPGSQL_DTYPE_ARRAYELEM:
+			/* always assignable? */
+			break;
 		case PLPGSQL_DTYPE_TRIGARG:
 			yyerror("cannot assign to tg_argv");
 			break;

src/pl/plpgsql/src/pl_exec.c

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.82 2003/03/25 00:34:23 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.83 2003/03/25 03:16:40 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -49,6 +49,7 @@
 #include "optimizer/clauses.h"
 #include "parser/parse_expr.h"
 #include "tcop/tcopprot.h"
+#include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
 #include "utils/syscache.h"
@@ -136,6 +137,9 @@ static void exec_eval_datum(PLpgSQL_execstate *estate,
 							Oid *typeid,
 							Datum *value,
 							bool *isnull);
+static int exec_eval_subscript(PLpgSQL_execstate * estate,
+							   PLpgSQL_expr * expr,
+							   bool *isNull);
 static Datum exec_eval_expr(PLpgSQL_execstate * estate,
 			   PLpgSQL_expr * expr,
 			   bool *isNull,
@@ -152,6 +156,9 @@ static Datum exec_cast_value(Datum value, Oid valtype,
 				Oid reqtypelem,
 				int32 reqtypmod,
 				bool *isnull);
+static Datum exec_simple_cast_value(Datum value, Oid valtype,
+									Oid reqtype, int32 reqtypmod,
+									bool *isnull);
 static void exec_init_tuple_store(PLpgSQL_execstate * estate);
 static bool compatible_tupdesc(TupleDesc td1, TupleDesc td2);
 static void exec_set_found(PLpgSQL_execstate * estate, bool state);
@@ -237,6 +244,7 @@ plpgsql_exec_function(PLpgSQL_function * func, FunctionCallInfo fcinfo)
 
 			case PLPGSQL_DTYPE_ROW:
 			case PLPGSQL_DTYPE_RECFIELD:
+			case PLPGSQL_DTYPE_ARRAYELEM:
 				estate.datums[i] = func->datums[i];
 				break;
 
@@ -308,6 +316,7 @@ plpgsql_exec_function(PLpgSQL_function * func, FunctionCallInfo fcinfo)
 			case PLPGSQL_DTYPE_ROW:
 			case PLPGSQL_DTYPE_REC:
 			case PLPGSQL_DTYPE_RECFIELD:
+			case PLPGSQL_DTYPE_ARRAYELEM:
 				break;
 
 			default:
@@ -507,6 +516,7 @@ plpgsql_exec_trigger(PLpgSQL_function * func,
 
 			case PLPGSQL_DTYPE_ROW:
 			case PLPGSQL_DTYPE_RECFIELD:
+			case PLPGSQL_DTYPE_ARRAYELEM:
 			case PLPGSQL_DTYPE_TRIGARG:
 				estate.datums[i] = func->datums[i];
 				break;
@@ -658,6 +668,7 @@ plpgsql_exec_trigger(PLpgSQL_function * func,
 			case PLPGSQL_DTYPE_ROW:
 			case PLPGSQL_DTYPE_REC:
 			case PLPGSQL_DTYPE_RECFIELD:
+			case PLPGSQL_DTYPE_ARRAYELEM:
 			case PLPGSQL_DTYPE_TRIGARG:
 				break;
 
@@ -822,6 +833,7 @@ exec_stmt_block(PLpgSQL_execstate * estate, PLpgSQL_stmt_block * block)
 				break;
 
 			case PLPGSQL_DTYPE_RECFIELD:
+			case PLPGSQL_DTYPE_ARRAYELEM:
 				break;
 
 			default:
@@ -1693,24 +1705,11 @@ exec_stmt_return_next(PLpgSQL_execstate * estate,
 								&rettype);
 
 		/* coerce type if needed */
-		if (!isNull && rettype != tupdesc->attrs[0]->atttypid)
+		retval = exec_simple_cast_value(retval,
-		{
-			Oid			targType = tupdesc->attrs[0]->atttypid;
-			Oid			typInput;
-			Oid			typElem;
-			FmgrInfo	finfo_input;
-
-			getTypeInputInfo(targType, &typInput, &typElem);
-			fmgr_info(typInput, &finfo_input);
-
-			retval = exec_cast_value(retval,
 										rettype,
-									 targType,
+										tupdesc->attrs[0]->atttypid,
-									 &finfo_input,
-									 typElem,
 										tupdesc->attrs[0]->atttypmod,
 										&isNull);
-		}
 
 		nullflag = isNull ? 'n' : ' ';
 
@@ -2709,10 +2708,21 @@ exec_assign_value(PLpgSQL_execstate * estate,
 	bool		attisnull;
 	Oid			atttype;
 	int32		atttypmod;
+	int			nsubscripts;
+	PLpgSQL_expr *subscripts[MAXDIM];
+	int			subscriptvals[MAXDIM];
+	bool		havenullsubscript,
+				oldarrayisnull;
+	Oid			arraytypeid,
+				arrayelemtypeid,
+				arrayInputFn;
+	int16		elemtyplen;
+	bool		elemtypbyval;
+	char		elemtypalign;
+	Datum		oldarrayval,
+				coerced_value;
+	ArrayType  *newarrayval;
 	HeapTuple	newtup;
-	Oid			typInput;
-	Oid			typElem;
-	FmgrInfo	finfo_input;
 
 	switch (target->dtype)
 	{
@@ -2812,15 +2822,10 @@ exec_assign_value(PLpgSQL_execstate * estate,
 			 */
 			atttype = SPI_gettypeid(rec->tupdesc, fno + 1);
 			atttypmod = rec->tupdesc->attrs[fno]->atttypmod;
-			getTypeInputInfo(atttype, &typInput, &typElem);
-			fmgr_info(typInput, &finfo_input);
-
 			attisnull = *isNull;
-			values[fno] = exec_cast_value(value,
+			values[fno] = exec_simple_cast_value(value,
 												 valtype,
 												 atttype,
-										  &finfo_input,
-										  typElem,
 												 atttypmod,
 												 &attisnull);
 			if (attisnull)
@@ -2829,7 +2834,7 @@ exec_assign_value(PLpgSQL_execstate * estate,
 				nulls[fno] = ' ';
 
 			/*
-			 * Avoid leaking the result of exec_cast_value, if it
+			 * Avoid leaking the result of exec_simple_cast_value, if it
 			 * performed a conversion to a pass-by-ref type.
 			 */
 			if (!attisnull && values[fno] != value && !get_typbyval(atttype))
@@ -2856,6 +2861,103 @@ exec_assign_value(PLpgSQL_execstate * estate,
 
 			break;
 
+		case PLPGSQL_DTYPE_ARRAYELEM:
+
+			/*
+			 * Target is an element of an array
+			 *
+			 * To handle constructs like x[1][2] := something, we have to
+			 * be prepared to deal with a chain of arrayelem datums.
+			 * Chase back to find the base array datum, and save the
+			 * subscript expressions as we go.  (We are scanning right to
+			 * left here, but want to evaluate the subscripts left-to-right
+			 * to minimize surprises.)
+			 */
+			nsubscripts = 0;
+			do {
+				PLpgSQL_arrayelem *arrayelem = (PLpgSQL_arrayelem *) target;
+
+				if (nsubscripts >= MAXDIM)
+					elog(ERROR, "Too many subscripts");
+				subscripts[nsubscripts++] = arrayelem->subscript;
+				target = estate->datums[arrayelem->arrayparentno];
+			} while (target->dtype == PLPGSQL_DTYPE_ARRAYELEM);
+
+			/* Fetch current value of array datum */
+			exec_eval_datum(estate, target, InvalidOid,
+							&arraytypeid, &oldarrayval, &oldarrayisnull);
+
+			getTypeInputInfo(arraytypeid, &arrayInputFn, &arrayelemtypeid);
+			if (!OidIsValid(arrayelemtypeid))
+				elog(ERROR, "Subscripted item is not an array");
+
+			/* Evaluate the subscripts, switch into left-to-right order */
+			havenullsubscript = false;
+			for (i = 0; i < nsubscripts; i++)
+			{
+				bool	subisnull;
+
+				subscriptvals[i] =
+					exec_eval_subscript(estate,
+										subscripts[nsubscripts-1-i],
+										&subisnull);
+				havenullsubscript |= subisnull;
+			}
+
+			/*
+			 * Skip the assignment if we have any nulls, either in the
+			 * original array value, the subscripts, or the righthand side.
+			 * This is pretty bogus but it corresponds to the current
+			 * behavior of ExecEvalArrayRef().
+			 */
+			if (oldarrayisnull || havenullsubscript || *isNull)
+				return;
+
+			/* Coerce source value to match array element type. */
+			coerced_value = exec_simple_cast_value(value,
+												   valtype,
+												   arrayelemtypeid,
+												   -1,
+												   isNull);
+
+			/*
+			 * Build the modified array value.
+			 */
+			get_typlenbyvalalign(arrayelemtypeid,
+								 &elemtyplen,
+								 &elemtypbyval,
+								 &elemtypalign);
+
+			newarrayval = array_set((ArrayType *) DatumGetPointer(oldarrayval),
+									nsubscripts,
+									subscriptvals,
+									coerced_value,
+									get_typlen(arraytypeid),
+									elemtyplen,
+									elemtypbyval,
+									elemtypalign,
+									isNull);
+
+			/*
+			 * Assign it to the base variable.
+			 */
+			exec_assign_value(estate, target,
+							  PointerGetDatum(newarrayval),
+							  arraytypeid, isNull);
+
+			/*
+			 * Avoid leaking the result of exec_simple_cast_value, if it
+			 * performed a conversion to a pass-by-ref type.
+			 */
+			if (!*isNull && coerced_value != value && !elemtypbyval)
+				pfree(DatumGetPointer(coerced_value));
+
+			/*
+			 * Avoid leaking the modified array value, too.
+			 */
+			pfree(newarrayval);
+			break;
+
 		default:
 			elog(ERROR, "unknown dtype %d in exec_assign_value()",
 				 target->dtype);
@@ -2888,7 +2990,6 @@ exec_eval_datum(PLpgSQL_execstate *estate,
 	PLpgSQL_recfield *recfield;
 	PLpgSQL_trigarg *trigarg;
 	int			tgargno;
-	Oid			tgargoid;
 	int			fno;
 
 	switch (datum->dtype)
@@ -2922,9 +3023,7 @@ exec_eval_datum(PLpgSQL_execstate *estate,
 		case PLPGSQL_DTYPE_TRIGARG:
 			trigarg = (PLpgSQL_trigarg *) datum;
 			*typeid = TEXTOID;
-			tgargno = (int) exec_eval_expr(estate, trigarg->argnum,
+			tgargno = exec_eval_subscript(estate, trigarg->argnum, isnull);
-										   isnull, &tgargoid);
-			exec_eval_cleanup(estate);
 			if (*isnull || tgargno < 0 || tgargno >= estate->trig_nargs)
 			{
 				*value = (Datum) 0;
@@ -2946,6 +3045,36 @@ exec_eval_datum(PLpgSQL_execstate *estate,
 	}
 }
 
+/* ----------
+ * exec_eval_subscript		Hack to allow subscripting of result variables.
+ *
+ * The caller may already have an open eval_econtext, which we have to
+ * save and restore around the call of exec_eval_expr.
+ * ----------
+ */
+static int
+exec_eval_subscript(PLpgSQL_execstate * estate,
+					PLpgSQL_expr * expr,
+					bool *isNull)
+{
+	ExprContext *save_econtext;
+	Datum		subscriptdatum;
+	Oid			subscripttypeid;
+	int			result;
+
+	save_econtext = estate->eval_econtext;
+	estate->eval_econtext = NULL;
+	subscriptdatum = exec_eval_expr(estate, expr, isNull, &subscripttypeid);
+	subscriptdatum = exec_simple_cast_value(subscriptdatum,
+											subscripttypeid,
+											INT4OID, -1,
+											isNull);
+	result = DatumGetInt32(subscriptdatum);
+	exec_eval_cleanup(estate);
+	estate->eval_econtext = save_econtext;
+	return result;
+}
+
 /* ----------
  * exec_eval_expr			Evaluate an expression and return
  *					the result Datum.
@@ -3323,6 +3452,43 @@ exec_cast_value(Datum value, Oid valtype,
 	return value;
 }
 
+/* ----------
+ * exec_simple_cast_value			Cast a value if required
+ *
+ * As above, but need not supply details about target type.  Note that this
+ * is slower than exec_cast_value with cached type info, and so should be
+ * avoided in heavily used code paths.
+ * ----------
+ */
+static Datum
+exec_simple_cast_value(Datum value, Oid valtype,
+					   Oid reqtype, int32 reqtypmod,
+					   bool *isnull)
+{
+	if (!*isnull)
+	{
+		if (valtype != reqtype || reqtypmod != -1)
+		{
+			Oid			typInput;
+			Oid			typElem;
+			FmgrInfo	finfo_input;
+
+			getTypeInputInfo(reqtype, &typInput, &typElem);
+			fmgr_info(typInput, &finfo_input);
+
+			value = exec_cast_value(value,
+									valtype,
+									reqtype,
+									&finfo_input,
+									typElem,
+									reqtypmod,
+									isnull);
+		}
+	}
+
+	return value;
+}
+
 
 /* ----------
  * exec_simple_check_node -		Recursively check if an expression

src/pl/plpgsql/src/pl_funcs.c

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_funcs.c,v 1.24 2003/03/25 00:34:23 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_funcs.c,v 1.25 2003/03/25 03:16:41 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -1023,6 +1023,12 @@ plpgsql_dumptree(PLpgSQL_function * func)
 					   ((PLpgSQL_recfield *) d)->fieldname,
 					   ((PLpgSQL_recfield *) d)->recparentno);
 				break;
+			case PLPGSQL_DTYPE_ARRAYELEM:
+				printf("ARRAYELEM of VAR %d subscript ", 
+					   ((PLpgSQL_arrayelem *) d)->arrayparentno);
+				dump_expr(((PLpgSQL_arrayelem *) d)->subscript);
+				printf("\n");
+				break;
 			case PLPGSQL_DTYPE_TRIGARG:
 				printf("TRIGARG ");
 				dump_expr(((PLpgSQL_trigarg *) d)->argnum);

src/pl/plpgsql/src/plpgsql.h

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.32 2003/03/25 00:34:24 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/plpgsql.h,v 1.33 2003/03/25 03:16:41 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -72,6 +72,7 @@ enum
 	PLPGSQL_DTYPE_ROW,
 	PLPGSQL_DTYPE_REC,
 	PLPGSQL_DTYPE_RECFIELD,
+	PLPGSQL_DTYPE_ARRAYELEM,
 	PLPGSQL_DTYPE_EXPR,
 	PLPGSQL_DTYPE_TRIGARG
 };
@@ -154,7 +155,8 @@ typedef struct
 
 /*
  * PLpgSQL_datum is the common supertype for PLpgSQL_expr, PLpgSQL_var,
- * PLpgSQL_row, PLpgSQL_rec, PLpgSQL_recfield, PLpgSQL_trigarg
+ * PLpgSQL_row, PLpgSQL_rec, PLpgSQL_recfield, PLpgSQL_arrayelem, and
+ * PLpgSQL_trigarg
  */
 typedef struct
 {								/* Generic datum array item		*/
@@ -231,10 +233,19 @@ typedef struct
 	int			dtype;
 	int			rfno;
 	char	   *fieldname;
-	int			recparentno;	/* recno of parent record */
+	int			recparentno;	/* dno of parent record */
 }	PLpgSQL_recfield;
 
 
+typedef struct
+{								/* Element of array variable */
+	int			dtype;
+	int			dno;
+	PLpgSQL_expr *subscript;
+	int			arrayparentno;	/* dno of parent array variable */
+}	PLpgSQL_arrayelem;
+
+
 typedef struct
 {								/* Positional argument to trigger	*/
 	int			dtype;