v1-0004-rewrite-plpgsql-assignment.patch

diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index c3ce480c8f..edea27697e 100644
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -1628,6 +1628,7 @@ CreateCast(CreateCastStmt *stmt)
 		case COERCION_ASSIGNMENT:
 			castcontext = COERCION_CODE_ASSIGNMENT;
 			break;
+			/* COERCION_PLPGSQL is intentionally not covered here */
 		case COERCION_EXPLICIT:
 			castcontext = COERCION_CODE_EXPLICIT;
 			break;
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index f529707458..eb0d9f51fb 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -2769,6 +2769,11 @@ _SPI_error_callback(void *arg)
 			case RAW_PARSE_PLPGSQL_EXPR:
 				errcontext("SQL expression \"%s\"", query);
 				break;
+			case RAW_PARSE_PLPGSQL_ASSIGN1:
+			case RAW_PARSE_PLPGSQL_ASSIGN2:
+			case RAW_PARSE_PLPGSQL_ASSIGN3:
+				errcontext("PL/pgSQL assignment \"%s\"", query);
+				break;
 			default:
 				errcontext("SQL statement \"%s\"", query);
 				break;
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 70f8b718e0..990daf1c98 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -3199,6 +3199,20 @@ _copySetOperationStmt(const SetOperationStmt *from)
 	return newnode;
 }
 
+static PLAssignStmt *
+_copyPLAssignStmt(const PLAssignStmt *from)
+{
+	PLAssignStmt *newnode = makeNode(PLAssignStmt);
+
+	COPY_STRING_FIELD(name);
+	COPY_NODE_FIELD(indirection);
+	COPY_SCALAR_FIELD(nnames);
+	COPY_NODE_FIELD(val);
+	COPY_LOCATION_FIELD(location);
+
+	return newnode;
+}
+
 static AlterTableStmt *
 _copyAlterTableStmt(const AlterTableStmt *from)
 {
@@ -5220,6 +5234,9 @@ copyObjectImpl(const void *from)
 		case T_SetOperationStmt:
 			retval = _copySetOperationStmt(from);
 			break;
+		case T_PLAssignStmt:
+			retval = _copyPLAssignStmt(from);
+			break;
 		case T_AlterTableStmt:
 			retval = _copyAlterTableStmt(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 541e0e6b48..7cbd31273d 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1085,6 +1085,18 @@ _equalSetOperationStmt(const SetOperationStmt *a, const SetOperationStmt *b)
 	return true;
 }
 
+static bool
+_equalPLAssignStmt(const PLAssignStmt *a, const PLAssignStmt *b)
+{
+	COMPARE_STRING_FIELD(name);
+	COMPARE_NODE_FIELD(indirection);
+	COMPARE_SCALAR_FIELD(nnames);
+	COMPARE_NODE_FIELD(val);
+	COMPARE_LOCATION_FIELD(location);
+
+	return true;
+}
+
 static bool
 _equalAlterTableStmt(const AlterTableStmt *a, const AlterTableStmt *b)
 {
@@ -3275,6 +3287,9 @@ equal(const void *a, const void *b)
 		case T_SetOperationStmt:
 			retval = _equalSetOperationStmt(a, b);
 			break;
+		case T_PLAssignStmt:
+			retval = _equalPLAssignStmt(a, b);
+			break;
 		case T_AlterTableStmt:
 			retval = _equalAlterTableStmt(a, b);
 			break;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 963f71e99d..f66d0e5fd5 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -3669,6 +3669,16 @@ raw_expression_tree_walker(Node *node,
 					return true;
 			}
 			break;
+		case T_PLAssignStmt:
+			{
+				PLAssignStmt *stmt = (PLAssignStmt *) node;
+
+				if (walker(stmt->indirection, context))
+					return true;
+				if (walker(stmt->val, context))
+					return true;
+			}
+			break;
 		case T_A_Expr:
 			{
 				A_Expr	   *expr = (A_Expr *) node;
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index d78b16ed1d..4871702f02 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2775,6 +2775,18 @@ _outSelectStmt(StringInfo str, const SelectStmt *node)
 	WRITE_NODE_FIELD(rarg);
 }
 
+static void
+_outPLAssignStmt(StringInfo str, const PLAssignStmt *node)
+{
+	WRITE_NODE_TYPE("PLASSIGN");
+
+	WRITE_STRING_FIELD(name);
+	WRITE_NODE_FIELD(indirection);
+	WRITE_INT_FIELD(nnames);
+	WRITE_NODE_FIELD(val);
+	WRITE_LOCATION_FIELD(location);
+}
+
 static void
 _outFuncCall(StringInfo str, const FuncCall *node)
 {
@@ -4211,6 +4223,9 @@ outNode(StringInfo str, const void *obj)
 			case T_SelectStmt:
 				_outSelectStmt(str, obj);
 				break;
+			case T_PLAssignStmt:
+				_outPLAssignStmt(str, obj);
+				break;
 			case T_ColumnDef:
 				_outColumnDef(str, obj);
 				break;
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 084e00f73d..bf2824c00f 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -42,8 +42,10 @@
 #include "parser/parse_param.h"
 #include "parser/parse_relation.h"
 #include "parser/parse_target.h"
+#include "parser/parse_type.h"
 #include "parser/parsetree.h"
 #include "rewrite/rewriteManip.h"
+#include "utils/builtins.h"
 #include "utils/rel.h"
 
 
@@ -70,6 +72,8 @@ static Query *transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt);
 static List *transformReturningList(ParseState *pstate, List *returningList);
 static List *transformUpdateTargetList(ParseState *pstate,
 									   List *targetList);
+static Query *transformPLAssignStmt(ParseState *pstate,
+									PLAssignStmt *stmt);
 static Query *transformDeclareCursorStmt(ParseState *pstate,
 										 DeclareCursorStmt *stmt);
 static Query *transformExplainStmt(ParseState *pstate,
@@ -304,6 +308,11 @@ transformStmt(ParseState *pstate, Node *parseTree)
 			}
 			break;
 
+		case T_PLAssignStmt:
+			result = transformPLAssignStmt(pstate,
+										   (PLAssignStmt *) parseTree);
+			break;
+
 			/*
 			 * Special cases
 			 */
@@ -367,6 +376,7 @@ analyze_requires_snapshot(RawStmt *parseTree)
 		case T_DeleteStmt:
 		case T_UpdateStmt:
 		case T_SelectStmt:
+		case T_PLAssignStmt:
 			result = true;
 			break;
 
@@ -2393,6 +2403,236 @@ transformReturningList(ParseState *pstate, List *returningList)
 }
 
 
+/*
+ * transformPLAssignStmt -
+ *	  transform a PL/pgSQL assignment statement
+ *
+ * If there is no opt_indirection, the transformed statement looks like
+ * "SELECT a_expr ...", except the expression has been cast to the type of
+ * the target.  With indirection, it's still a SELECT, but the expression will
+ * incorporate FieldStore and/or assignment SubscriptingRef nodes to compute a
+ * new value for a container-type variable represented by the target.  The
+ * expression references the target as the container source.
+ */
+static Query *
+transformPLAssignStmt(ParseState *pstate, PLAssignStmt *stmt)
+{
+	Query	   *qry = makeNode(Query);
+	ColumnRef  *cref = makeNode(ColumnRef);
+	List	   *indirection = stmt->indirection;
+	int			nnames = stmt->nnames;
+	SelectStmt *sstmt = stmt->val;
+	Node	   *target;
+	Oid			targettype;
+	int32		targettypmod;
+	Oid			targetcollation;
+	List	   *tlist;
+	TargetEntry *tle;
+	Oid			type_id;
+	Node	   *qual;
+	ListCell   *l;
+
+	/*
+	 * First, construct a ColumnRef for the target variable.  If the target
+	 * has more than one dotted name, we have to pull the extra names out of
+	 * the indirection list.
+	 */
+	cref->fields = list_make1(makeString(stmt->name));
+	cref->location = stmt->location;
+	if (nnames > 1)
+	{
+		/* avoid munging the raw parsetree */
+		indirection = list_copy(indirection);
+		while (--nnames > 0 && indirection != NIL)
+		{
+			Node	   *ind = (Node *) linitial(indirection);
+
+			if (!IsA(ind, String))
+				elog(ERROR, "invalid name count in PLAssignStmt");
+			cref->fields = lappend(cref->fields, ind);
+			indirection = list_delete_first(indirection);
+		}
+	}
+
+	/*
+	 * Transform the target reference.  Typically we will get back a Param
+	 * node, but there's no reason to be too picky about its type.
+	 */
+	target = transformExpr(pstate, (Node *) cref,
+						   EXPR_KIND_UPDATE_TARGET);
+	targettype = exprType(target);
+	targettypmod = exprTypmod(target);
+	targetcollation = exprCollation(target);
+
+	/*
+	 * The rest mostly matches transformSelectStmt, except that we needn't
+	 * consider WITH or DISTINCT, and we build a targetlist our own way.
+	 */
+	qry->commandType = CMD_SELECT;
+	pstate->p_is_insert = false;
+
+	/* make FOR UPDATE/FOR SHARE info available to addRangeTableEntry */
+	pstate->p_locking_clause = sstmt->lockingClause;
+
+	/* make WINDOW info available for window functions, too */
+	pstate->p_windowdefs = sstmt->windowClause;
+
+	/* process the FROM clause */
+	transformFromClause(pstate, sstmt->fromClause);
+
+	/* initially transform the targetlist as if in SELECT */
+	tlist = transformTargetList(pstate, sstmt->targetList,
+								EXPR_KIND_SELECT_TARGET);
+
+	/* we should have exactly one targetlist item */
+	if (list_length(tlist) != 1)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg_plural("assignment source returned %d column",
+							   "assignment source returned %d columns",
+							   list_length(tlist),
+							   list_length(tlist))));
+
+	tle = linitial_node(TargetEntry, tlist);
+
+	/*
+	 * This next bit is similar to transformAssignedExpr; the key difference
+	 * is we use COERCION_PLPGSQL not COERCION_ASSIGNMENT.
+	 */
+	type_id = exprType((Node *) tle->expr);
+
+	pstate->p_expr_kind = EXPR_KIND_UPDATE_TARGET;
+
+	if (indirection)
+	{
+		tle->expr = (Expr *)
+			transformAssignmentIndirection(pstate,
+										   target,
+										   stmt->name,
+										   false,
+										   targettype,
+										   targettypmod,
+										   targetcollation,
+										   indirection,
+										   list_head(indirection),
+										   (Node *) tle->expr,
+										   COERCION_PLPGSQL,
+										   exprLocation(target));
+	}
+	else if (targettype != type_id &&
+			 (targettype == RECORDOID || ISCOMPLEX(targettype)) &&
+			 (type_id == RECORDOID || ISCOMPLEX(type_id)))
+	{
+		/*
+		 * Hack: do not let coerce_to_target_type() deal with inconsistent
+		 * composite types.  Just pass the expression result through as-is,
+		 * and let the PL/pgSQL executor do the conversion its way.  This is
+		 * rather bogus, but it's needed for backwards compatibility.
+		 */
+	}
+	else
+	{
+		/*
+		 * For normal non-qualified target column, do type checking and
+		 * coercion.
+		 */
+		Node	   *orig_expr = (Node *) tle->expr;
+
+		tle->expr = (Expr *)
+			coerce_to_target_type(pstate,
+								  orig_expr, type_id,
+								  targettype, targettypmod,
+								  COERCION_PLPGSQL,
+								  COERCE_IMPLICIT_CAST,
+								  -1);
+		/* With COERCION_PLPGSQL, this error is probably unreachable */
+		if (tle->expr == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("variable \"%s\" is of type %s"
+							" but expression is of type %s",
+							stmt->name,
+							format_type_be(targettype),
+							format_type_be(type_id)),
+					 errhint("You will need to rewrite or cast the expression."),
+					 parser_errposition(pstate, exprLocation(orig_expr))));
+	}
+
+	pstate->p_expr_kind = EXPR_KIND_NONE;
+
+	qry->targetList = list_make1(tle);
+
+	/* transform WHERE */
+	qual = transformWhereClause(pstate, sstmt->whereClause,
+								EXPR_KIND_WHERE, "WHERE");
+
+	/* initial processing of HAVING clause is much like WHERE clause */
+	qry->havingQual = transformWhereClause(pstate, sstmt->havingClause,
+										   EXPR_KIND_HAVING, "HAVING");
+
+	/*
+	 * Transform sorting/grouping stuff.  Do ORDER BY first because both
+	 * transformGroupClause and transformDistinctClause need the results. Note
+	 * that these functions can also change the targetList, so it's passed to
+	 * them by reference.
+	 */
+	qry->sortClause = transformSortClause(pstate,
+										  sstmt->sortClause,
+										  &qry->targetList,
+										  EXPR_KIND_ORDER_BY,
+										  false /* allow SQL92 rules */ );
+
+	qry->groupClause = transformGroupClause(pstate,
+											sstmt->groupClause,
+											&qry->groupingSets,
+											&qry->targetList,
+											qry->sortClause,
+											EXPR_KIND_GROUP_BY,
+											false /* allow SQL92 rules */ );
+
+	/* No DISTINCT clause */
+	Assert(!sstmt->distinctClause);
+	qry->distinctClause = NIL;
+	qry->hasDistinctOn = false;
+
+	/* transform LIMIT */
+	qry->limitOffset = transformLimitClause(pstate, sstmt->limitOffset,
+											EXPR_KIND_OFFSET, "OFFSET",
+											sstmt->limitOption);
+	qry->limitCount = transformLimitClause(pstate, sstmt->limitCount,
+										   EXPR_KIND_LIMIT, "LIMIT",
+										   sstmt->limitOption);
+	qry->limitOption = sstmt->limitOption;
+
+	/* transform window clauses after we have seen all window functions */
+	qry->windowClause = transformWindowDefinitions(pstate,
+												   pstate->p_windowdefs,
+												   &qry->targetList);
+
+	qry->rtable = pstate->p_rtable;
+	qry->jointree = makeFromExpr(pstate->p_joinlist, qual);
+
+	qry->hasSubLinks = pstate->p_hasSubLinks;
+	qry->hasWindowFuncs = pstate->p_hasWindowFuncs;
+	qry->hasTargetSRFs = pstate->p_hasTargetSRFs;
+	qry->hasAggs = pstate->p_hasAggs;
+
+	foreach(l, sstmt->lockingClause)
+	{
+		transformLockingClause(pstate, qry,
+							   (LockingClause *) lfirst(l), false);
+	}
+
+	assign_query_collations(pstate, qry);
+
+	/* this must be done after collations, for reliable comparison of exprs */
+	if (pstate->p_hasAggs || qry->groupClause || qry->groupingSets || qry->havingQual)
+		parseCheckAggregates(pstate, qry);
+
+	return qry;
+}
+
+
 /*
  * transformDeclareCursorStmt -
  *	transform a DECLARE CURSOR Statement
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 4c58b46651..9101435f7b 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -294,7 +294,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 %type <node>	select_no_parens select_with_parens select_clause
 				simple_select values_clause
-				PLpgSQL_Expr
+				PLpgSQL_Expr PLAssignStmt
 
 %type <node>	alter_column_default opclass_item opclass_drop alter_using
 %type <ival>	add_drop opt_asc_desc opt_nulls_order
@@ -536,7 +536,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <str>		ColId ColLabel BareColLabel
 %type <str>		NonReservedWord NonReservedWord_or_Sconst
 %type <str>		var_name type_function_name param_name
-%type <str>		createdb_opt_name
+%type <str>		createdb_opt_name plassign_target
 %type <node>	var_value zone_value
 %type <rolespec> auth_ident RoleSpec opt_granted_by
 
@@ -733,6 +733,9 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  */
 %token		MODE_TYPE_NAME
 %token		MODE_PLPGSQL_EXPR
+%token		MODE_PLPGSQL_ASSIGN1
+%token		MODE_PLPGSQL_ASSIGN2
+%token		MODE_PLPGSQL_ASSIGN3
 
 
 /* Precedence: lowest to highest */
@@ -815,6 +818,27 @@ stmtblock:	stmtmulti
 				pg_yyget_extra(yyscanner)->parsetree =
 					list_make1(makeRawStmt($2, 0));
 			}
+			| MODE_PLPGSQL_ASSIGN1 PLAssignStmt
+			{
+				PLAssignStmt *n = (PLAssignStmt *) $2;
+				n->nnames = 1;
+				pg_yyget_extra(yyscanner)->parsetree =
+					list_make1(makeRawStmt((Node *) n, 0));
+			}
+			| MODE_PLPGSQL_ASSIGN2 PLAssignStmt
+			{
+				PLAssignStmt *n = (PLAssignStmt *) $2;
+				n->nnames = 2;
+				pg_yyget_extra(yyscanner)->parsetree =
+					list_make1(makeRawStmt((Node *) n, 0));
+			}
+			| MODE_PLPGSQL_ASSIGN3 PLAssignStmt
+			{
+				PLAssignStmt *n = (PLAssignStmt *) $2;
+				n->nnames = 3;
+				pg_yyget_extra(yyscanner)->parsetree =
+					list_make1(makeRawStmt((Node *) n, 0));
+			}
 		;
 
 /*
@@ -15069,6 +15093,31 @@ PLpgSQL_Expr: opt_target_list
 				}
 		;
 
+/*
+ * PL/pgSQL Assignment statement: name opt_indirection := PLpgSQL_Expr
+ */
+
+PLAssignStmt: plassign_target opt_indirection plassign_equals PLpgSQL_Expr
+				{
+					PLAssignStmt *n = makeNode(PLAssignStmt);
+
+					n->name = $1;
+					n->indirection = check_indirection($2, yyscanner);
+					/* nnames will be filled by calling production */
+					n->val = (SelectStmt *) $4;
+					n->location = @1;
+					$$ = (Node *) n;
+				}
+		;
+
+plassign_target: ColId							{ $$ = $1; }
+			| PARAM								{ $$ = psprintf("$%d", $1); }
+		;
+
+plassign_equals: COLON_EQUALS
+			| '='
+		;
+
 
 /*
  * Name classification hierarchy.
diff --git a/src/backend/parser/parse_coerce.c b/src/backend/parser/parse_coerce.c
index da6c3ae4b5..462e2af74e 100644
--- a/src/backend/parser/parse_coerce.c
+++ b/src/backend/parser/parse_coerce.c
@@ -2815,6 +2815,14 @@ find_coercion_pathway(Oid targetTypeId, Oid sourceTypeId,
 		}
 	}
 
+	/*
+	 * When parsing PL/pgSQL assignments, allow an I/O cast to be used
+	 * whenever no normal coercion is available.
+	 */
+	if (result == COERCION_PATH_NONE &&
+		ccontext == COERCION_PLPGSQL)
+		result = COERCION_PATH_COERCEVIAIO;
+
 	return result;
 }
 
diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index 3dda8e2847..8f2b0f18e0 100644
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -34,17 +34,6 @@
 
 static void markTargetListOrigin(ParseState *pstate, TargetEntry *tle,
 								 Var *var, int levelsup);
-static Node *transformAssignmentIndirection(ParseState *pstate,
-											Node *basenode,
-											const char *targetName,
-											bool targetIsSubscripting,
-											Oid targetTypeId,
-											int32 targetTypMod,
-											Oid targetCollation,
-											List *indirection,
-											ListCell *indirection_cell,
-											Node *rhs,
-											int location);
 static Node *transformAssignmentSubscripts(ParseState *pstate,
 										   Node *basenode,
 										   const char *targetName,
@@ -56,6 +45,7 @@ static Node *transformAssignmentSubscripts(ParseState *pstate,
 										   List *indirection,
 										   ListCell *next_indirection,
 										   Node *rhs,
+										   CoercionContext ccontext,
 										   int location);
 static List *ExpandColumnRefStar(ParseState *pstate, ColumnRef *cref,
 								 bool make_target_entry);
@@ -561,6 +551,7 @@ transformAssignedExpr(ParseState *pstate,
 										   indirection,
 										   list_head(indirection),
 										   (Node *) expr,
+										   COERCION_ASSIGNMENT,
 										   location);
 	}
 	else
@@ -642,15 +633,15 @@ updateTargetListEntry(ParseState *pstate,
 
 /*
  * Process indirection (field selection or subscripting) of the target
- * column in INSERT/UPDATE.  This routine recurses for multiple levels
- * of indirection --- but note that several adjacent A_Indices nodes in
- * the indirection list are treated as a single multidimensional subscript
+ * column in INSERT/UPDATE/assignment.  This routine recurses for multiple
+ * levels of indirection --- but note that several adjacent A_Indices nodes
+ * in the indirection list are treated as a single multidimensional subscript
  * operation.
  *
  * In the initial call, basenode is a Var for the target column in UPDATE,
- * or a null Const of the target's type in INSERT.  In recursive calls,
- * basenode is NULL, indicating that a substitute node should be consed up if
- * needed.
+ * or a null Const of the target's type in INSERT, or a Param for the target
+ * variable in PL/pgSQL assignment.  In recursive calls, basenode is NULL,
+ * indicating that a substitute node should be consed up if needed.
  *
  * targetName is the name of the field or subfield we're assigning to, and
  * targetIsSubscripting is true if we're subscripting it.  These are just for
@@ -667,12 +658,16 @@ updateTargetListEntry(ParseState *pstate,
  * rhs is the already-transformed value to be assigned; note it has not been
  * coerced to any particular type.
  *
+ * ccontext is the coercion level to use while coercing the rhs.  For
+ * normal statements it'll be COERCION_ASSIGNMENT, but PL/pgSQL uses
+ * a special value.
+ *
  * location is the cursor error position for any errors.  (Note: this points
  * to the head of the target clause, eg "foo" in "foo.bar[baz]".  Later we
  * might want to decorate indirection cells with their own location info,
  * in which case the location argument could probably be dropped.)
  */
-static Node *
+Node *
 transformAssignmentIndirection(ParseState *pstate,
 							   Node *basenode,
 							   const char *targetName,
@@ -683,6 +678,7 @@ transformAssignmentIndirection(ParseState *pstate,
 							   List *indirection,
 							   ListCell *indirection_cell,
 							   Node *rhs,
+							   CoercionContext ccontext,
 							   int location)
 {
 	Node	   *result;
@@ -757,6 +753,7 @@ transformAssignmentIndirection(ParseState *pstate,
 													 indirection,
 													 i,
 													 rhs,
+													 ccontext,
 													 location);
 			}
 
@@ -807,6 +804,7 @@ transformAssignmentIndirection(ParseState *pstate,
 												 indirection,
 												 lnext(indirection, i),
 												 rhs,
+												 ccontext,
 												 location);
 
 			/* and build a FieldStore node */
@@ -845,6 +843,7 @@ transformAssignmentIndirection(ParseState *pstate,
 											 indirection,
 											 NULL,
 											 rhs,
+											 ccontext,
 											 location);
 	}
 
@@ -853,7 +852,7 @@ transformAssignmentIndirection(ParseState *pstate,
 	result = coerce_to_target_type(pstate,
 								   rhs, exprType(rhs),
 								   targetTypeId, targetTypMod,
-								   COERCION_ASSIGNMENT,
+								   ccontext,
 								   COERCE_IMPLICIT_CAST,
 								   -1);
 	if (result == NULL)
@@ -898,6 +897,7 @@ transformAssignmentSubscripts(ParseState *pstate,
 							  List *indirection,
 							  ListCell *next_indirection,
 							  Node *rhs,
+							  CoercionContext ccontext,
 							  int location)
 {
 	Node	   *result;
@@ -949,6 +949,7 @@ transformAssignmentSubscripts(ParseState *pstate,
 										 indirection,
 										 next_indirection,
 										 rhs,
+										 ccontext,
 										 location);
 
 	/*
@@ -969,7 +970,7 @@ transformAssignmentSubscripts(ParseState *pstate,
 		result = coerce_to_target_type(pstate,
 									   result, resulttype,
 									   targetTypeId, targetTypMod,
-									   COERCION_ASSIGNMENT,
+									   ccontext,
 									   COERCE_IMPLICIT_CAST,
 									   -1);
 		/* can fail if we had int2vector/oidvector, but not for true domains */
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index 71df8ef022..291706c593 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -58,7 +58,10 @@ raw_parser(const char *str, RawParseMode mode)
 		static const int mode_token[] = {
 			0,					/* RAW_PARSE_DEFAULT */
 			MODE_TYPE_NAME,		/* RAW_PARSE_TYPE_NAME */
-			MODE_PLPGSQL_EXPR	/* RAW_PARSE_PLPGSQL_EXPR */
+			MODE_PLPGSQL_EXPR,	/* RAW_PARSE_PLPGSQL_EXPR */
+			MODE_PLPGSQL_ASSIGN1,	/* RAW_PARSE_PLPGSQL_ASSIGN1 */
+			MODE_PLPGSQL_ASSIGN2,	/* RAW_PARSE_PLPGSQL_ASSIGN2 */
+			MODE_PLPGSQL_ASSIGN3	/* RAW_PARSE_PLPGSQL_ASSIGN3 */
 		};
 
 		yyextra.have_lookahead = true;
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index a42ead7d69..fdcabe6a48 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -2313,6 +2313,10 @@ CreateCommandTag(Node *parsetree)
 			tag = CMDTAG_SELECT;
 			break;
 
+		case T_PLAssignStmt:
+			tag = CMDTAG_SELECT;
+			break;
+
 			/* utility statements --- same whether raw or cooked */
 		case T_TransactionStmt:
 			{
@@ -3181,6 +3185,10 @@ GetCommandLogLevel(Node *parsetree)
 				lev = LOGSTMT_ALL;
 			break;
 
+		case T_PLAssignStmt:
+			lev = LOGSTMT_ALL;
+			break;
+
 			/* utility statements --- same whether raw or cooked */
 		case T_TransactionStmt:
 			lev = LOGSTMT_ALL;
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index 3684f87a88..2d445d03db 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -314,6 +314,7 @@ typedef enum NodeTag
 	T_DeleteStmt,
 	T_UpdateStmt,
 	T_SelectStmt,
+	T_PLAssignStmt,
 	T_AlterTableStmt,
 	T_AlterTableCmd,
 	T_AlterDomainStmt,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 48a79a7657..8e09a457ab 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1675,6 +1675,25 @@ typedef struct SetOperationStmt
 } SetOperationStmt;
 
 
+/* ----------------------
+ *		PL/pgSQL Assignment Statement
+ *
+ * Like SelectStmt, this is transformed into a SELECT Query.
+ * However, the targetlist of the result looks more like an UPDATE.
+ * ----------------------
+ */
+typedef struct PLAssignStmt
+{
+	NodeTag		type;
+
+	char	   *name;			/* initial column name */
+	List	   *indirection;	/* subscripts and field names, if any */
+	int			nnames;			/* number of names to use in ColumnRef */
+	SelectStmt *val;			/* the PL/pgSQL expression to assign */
+	int			location;		/* name's token location, or -1 if unknown */
+} PLAssignStmt;
+
+
 /*****************************************************************************
  *		Other Statements (no optimizations required)
  *
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index dd85908fe2..71a58804dc 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -457,6 +457,7 @@ typedef enum CoercionContext
 {
 	COERCION_IMPLICIT,			/* coercion in context of expression */
 	COERCION_ASSIGNMENT,		/* coercion in context of assignment */
+	COERCION_PLPGSQL,			/* if no assignment cast, use CoerceViaIO */
 	COERCION_EXPLICIT			/* explicit cast operation */
 } CoercionContext;
 
diff --git a/src/include/parser/parse_target.h b/src/include/parser/parse_target.h
index 7039df29cb..5ce8c3666e 100644
--- a/src/include/parser/parse_target.h
+++ b/src/include/parser/parse_target.h
@@ -36,6 +36,18 @@ extern void updateTargetListEntry(ParseState *pstate, TargetEntry *tle,
 								  char *colname, int attrno,
 								  List *indirection,
 								  int location);
+extern Node *transformAssignmentIndirection(ParseState *pstate,
+											Node *basenode,
+											const char *targetName,
+											bool targetIsSubscripting,
+											Oid targetTypeId,
+											int32 targetTypMod,
+											Oid targetCollation,
+											List *indirection,
+											ListCell *indirection_cell,
+											Node *rhs,
+											CoercionContext ccontext,
+											int location);
 extern List *checkInsertTargets(ParseState *pstate, List *cols,
 								List **attrnos);
 extern TupleDesc expandRecordVariable(ParseState *pstate, Var *var,
diff --git a/src/include/parser/parser.h b/src/include/parser/parser.h
index 3b7dab17ef..ac89f2b93f 100644
--- a/src/include/parser/parser.h
+++ b/src/include/parser/parser.h
@@ -29,12 +29,19 @@
  *
  * RAW_PARSE_PLPGSQL_EXPR: parse a PL/pgSQL expression, and return
  * a one-element List containing a RawStmt node.
+ *
+ * RAW_PARSE_PLPGSQL_ASSIGNn: parse a PL/pgSQL assignment statement,
+ * and return a one-element List containing a RawStmt node.  "n"
+ * gives the number of dotted names comprising the target ColumnRef.
  */
 typedef enum
 {
 	RAW_PARSE_DEFAULT = 0,
 	RAW_PARSE_TYPE_NAME,
-	RAW_PARSE_PLPGSQL_EXPR
+	RAW_PARSE_PLPGSQL_EXPR,
+	RAW_PARSE_PLPGSQL_ASSIGN1,
+	RAW_PARSE_PLPGSQL_ASSIGN2,
+	RAW_PARSE_PLPGSQL_ASSIGN3
 } RawParseMode;
 
 /* Values for the backslash_quote GUC */
diff --git a/src/interfaces/ecpg/preproc/parse.pl b/src/interfaces/ecpg/preproc/parse.pl
index 2b254c2b77..cea6dd6517 100644
--- a/src/interfaces/ecpg/preproc/parse.pl
+++ b/src/interfaces/ecpg/preproc/parse.pl
@@ -71,7 +71,10 @@ my %replace_types = (
 	'type_function_name' => 'ignore',
 	'ColLabel'           => 'ignore',
 	'Sconst'             => 'ignore',
-	'PLpgSQL_Expr'       => 'ignore',);
+	'PLpgSQL_Expr'       => 'ignore',
+	'PLAssignStmt'       => 'ignore',
+	'plassign_target'    => 'ignore',
+	'plassign_equals'    => 'ignore',);
 
 # these replace_line commands excise certain keywords from the core keyword
 # lists.  Be sure to account for these in ColLabel and related productions.
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index f56dcd0e79..cb5c7f9fea 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -8008,10 +8008,14 @@ get_cast_hashentry(PLpgSQL_execstate *estate,
 		placeholder->collation = get_typcollation(srctype);
 
 		/*
-		 * Apply coercion.  We use ASSIGNMENT coercion because that's the
-		 * closest match to plpgsql's historical behavior; in particular,
-		 * EXPLICIT coercion would allow silent truncation to a destination
-		 * varchar/bpchar's length, which we do not want.
+		 * Apply coercion.  We use the special coercion context
+		 * COERCION_PLPGSQL to match plpgsql's historical behavior, namely
+		 * that any cast not available at ASSIGNMENT level will be implemented
+		 * as an I/O coercion.  (It's somewhat dubious that we prefer I/O
+		 * coercion over cast pathways that exist at EXPLICIT level.  Changing
+		 * that would cause assorted minor behavioral differences though, and
+		 * a user who wants the explicit-cast behavior can always write an
+		 * explicit cast.)
 		 *
 		 * If source type is UNKNOWN, coerce_to_target_type will fail (it only
 		 * expects to see that for Const input nodes), so don't call it; we'll
@@ -8024,7 +8028,7 @@ get_cast_hashentry(PLpgSQL_execstate *estate,
 			cast_expr = coerce_to_target_type(NULL,
 											  (Node *) placeholder, srctype,
 											  dsttype, dsttypmod,
-											  COERCION_ASSIGNMENT,
+											  COERCION_PLPGSQL,
 											  COERCE_IMPLICIT_CAST,
 											  -1);
 
@@ -8032,7 +8036,8 @@ get_cast_hashentry(PLpgSQL_execstate *estate,
 		 * If there's no cast path according to the parser, fall back to using
 		 * an I/O coercion; this is semantically dubious but matches plpgsql's
 		 * historical behavior.  We would need something of the sort for
-		 * UNKNOWN literals in any case.
+		 * UNKNOWN literals in any case.  (This is probably now only reachable
+		 * in the case where srctype is UNKNOWN/RECORD.)
 		 */
 		if (cast_expr == NULL)
 		{
@@ -8341,7 +8346,8 @@ exec_check_rw_parameter(PLpgSQL_expr *expr, int target_dno)
 		return;
 
 	/*
-	 * Top level of expression must be a simple FuncExpr or OpExpr.
+	 * Top level of expression must be a simple FuncExpr, OpExpr, or
+	 * SubscriptingRef.
 	 */
 	if (IsA(expr->expr_simple_expr, FuncExpr))
 	{
@@ -8357,6 +8363,33 @@ exec_check_rw_parameter(PLpgSQL_expr *expr, int target_dno)
 		funcid = opexpr->opfuncid;
 		fargs = opexpr->args;
 	}
+	else if (IsA(expr->expr_simple_expr, SubscriptingRef))
+	{
+		SubscriptingRef *sbsref = (SubscriptingRef *) expr->expr_simple_expr;
+
+		/* We only trust standard varlena arrays to be safe */
+		if (get_typsubscript(sbsref->refcontainertype, NULL) !=
+			F_ARRAY_SUBSCRIPT_HANDLER)
+			return;
+
+		/* refexpr can be a simple Param, otherwise must not contain target */
+		if (!(sbsref->refexpr && IsA(sbsref->refexpr, Param)) &&
+			contains_target_param((Node *) sbsref->refexpr, &target_dno))
+			return;
+
+		/* the other subexpressions must not contain target */
+		if (contains_target_param((Node *) sbsref->refupperindexpr,
+								  &target_dno) ||
+			contains_target_param((Node *) sbsref->reflowerindexpr,
+								  &target_dno) ||
+			contains_target_param((Node *) sbsref->refassgnexpr,
+								  &target_dno))
+			return;
+
+		/* OK, we can pass target as a read-write parameter */
+		expr->rwparam = target_dno;
+		return;
+	}
 	else
 		return;
 
diff --git a/src/pl/plpgsql/src/pl_gram.y b/src/pl/plpgsql/src/pl_gram.y
index 3b36220d73..051544a3b4 100644
--- a/src/pl/plpgsql/src/pl_gram.y
+++ b/src/pl/plpgsql/src/pl_gram.y
@@ -973,16 +973,40 @@ stmt_call		: K_CALL
 					}
 				;
 
-stmt_assign		: assign_var assign_operator expr_until_semi
+stmt_assign		: T_DATUM
 					{
 						PLpgSQL_stmt_assign *new;
+						RawParseMode pmode;
 
+						/* see how many names identify the datum */
+						switch ($1.ident ? 1 : list_length($1.idents))
+						{
+							case 1:
+								pmode = RAW_PARSE_PLPGSQL_ASSIGN1;
+								break;
+							case 2:
+								pmode = RAW_PARSE_PLPGSQL_ASSIGN2;
+								break;
+							case 3:
+								pmode = RAW_PARSE_PLPGSQL_ASSIGN3;
+								break;
+							default:
+								elog(ERROR, "unexpected number of names");
+								pmode = 0; /* keep compiler quiet */
+						}
+
+						check_assignable($1.datum, @1);
 						new = palloc0(sizeof(PLpgSQL_stmt_assign));
 						new->cmd_type = PLPGSQL_STMT_ASSIGN;
 						new->lineno   = plpgsql_location_to_lineno(@1);
 						new->stmtid = ++plpgsql_curr_compile->nstatements;
-						new->varno = $1->dno;
-						new->expr  = $3;
+						new->varno = $1.datum->dno;
+						/* Push back the head name to include it in the stmt */
+						plpgsql_push_back_token(T_DATUM);
+						new->expr = read_sql_construct(';', 0, 0, ";",
+													   pmode,
+													   false, true, true,
+													   NULL, NULL);
 
 						$$ = (PLpgSQL_stmt *)new;
 					}