Fix deparsing of ON CONFLICT arbiter WHERE clauses.

The parser doesn't allow qualification of column names appearing in
these clauses, but ruleutils.c would sometimes qualify them, leading
to dump/reload failures.  Per bug #13891 from Onder Kalaci.

(In passing, make stanzas in ruleutils.c that save/restore varprefix
more consistent.)

Peter Geoghegan

src/backend/utils/adt/ruleutils.c

@@ -5532,9 +5532,21 @@ get_insert_query_def(Query *query, deparse_context *context)
 			/* Add a WHERE clause (for partial indexes) if given */
 			if (confl->arbiterWhere != NULL)
 			{
+				bool		save_varprefix;
+
+				/*
+				 * Force non-prefixing of Vars, since parser assumes that they
+				 * belong to target relation.  WHERE clause does not use
+				 * InferenceElem, so this is separately required.
+				 */
+				save_varprefix = context->varprefix;
+				context->varprefix = false;
+
 				appendContextKeyword(context, " WHERE ",
 									 -PRETTYINDENT_STD, PRETTYINDENT_STD, 1);
 				get_rule_expr(confl->arbiterWhere, context, false);
+
+				context->varprefix = save_varprefix;
 			}
 		}
 		else if (confl->constraint != InvalidOid)
@@ -7956,13 +7968,14 @@ get_rule_expr(Node *node, deparse_context *context,
 		case T_InferenceElem:
 			{
 				InferenceElem *iexpr = (InferenceElem *) node;
-				bool		varprefix = context->varprefix;
+				bool		save_varprefix;
 				bool		need_parens;
 
 				/*
 				 * InferenceElem can only refer to target relation, so a
-				 * prefix is never useful.
+				 * prefix is not useful, and indeed would cause parse errors.
 				 */
+				save_varprefix = context->varprefix;
 				context->varprefix = false;
 
 				/*
@@ -7982,7 +7995,7 @@ get_rule_expr(Node *node, deparse_context *context,
 				if (need_parens)
 					appendStringInfoChar(buf, ')');
 
-				context->varprefix = varprefix;
+				context->varprefix = save_varprefix;
 
 				if (iexpr->infercollid)
 					appendStringInfo(buf, " COLLATE %s",

src/test/regress/expected/rules.out

@@ -2846,7 +2846,7 @@ SELECT definition FROM pg_rules WHERE tablename = 'hats' ORDER BY rulename;
  CREATE RULE hat_nosert AS                                                                  +
      ON INSERT TO hats DO INSTEAD  INSERT INTO hat_data (hat_name, hat_color)               +
    VALUES (new.hat_name, new.hat_color) ON CONFLICT(hat_name COLLATE "C" bpchar_pattern_ops)+
-   WHERE (hat_data.hat_color = 'green'::bpchar) DO NOTHING                                  +
+   WHERE (hat_color = 'green'::bpchar) DO NOTHING                                           +
    RETURNING hat_data.hat_name,                                                             +
      hat_data.hat_color;
 (1 row)
@@ -2871,7 +2871,7 @@ SELECT tablename, rulename, definition FROM pg_rules
  hats      | hat_nosert | CREATE RULE hat_nosert AS                                                                  +
            |            |     ON INSERT TO hats DO INSTEAD  INSERT INTO hat_data (hat_name, hat_color)               +
            |            |   VALUES (new.hat_name, new.hat_color) ON CONFLICT(hat_name COLLATE "C" bpchar_pattern_ops)+
-           |            |   WHERE (hat_data.hat_color = 'green'::bpchar) DO NOTHING                                  +
+           |            |   WHERE (hat_color = 'green'::bpchar) DO NOTHING                                           +
            |            |   RETURNING hat_data.hat_name,                                                             +
            |            |     hat_data.hat_color;
 (1 row)