Various fixes around ON CONFLICT for rule deparsing.

Neither the deparsing of the new alias for INSERT's target table, nor of
the inference clause was supported. Also fixup a typo in an error
message.

Add regression tests to test those code paths.

Author: Peter Geoghegan

src/backend/parser/parse_clause.c

@@ -2765,7 +2765,7 @@ transformOnConflictArbiter(ParseState *pstate,
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("ON CONFLICT DO UPDATE requires inference specification or constraint name"),
-				 errhint("For example, ON CONFLICT ON CONFLICT (<column>)."),
+				 errhint("For example, ON CONFLICT (<column>)."),
 				 parser_errposition(pstate,
 									exprLocation((Node *) onConflictClause))));
 

src/backend/utils/adt/ruleutils.c

@@ -5392,6 +5392,10 @@ get_insert_query_def(Query *query, deparse_context *context)
 	}
 	appendStringInfo(buf, "INSERT INTO %s ",
 					 generate_relation_name(rte->relid, NIL));
+	/* INSERT requires AS keyword for target alias */
+	if (rte->alias != NULL)
+		appendStringInfo(buf, "AS %s ",
+						 quote_identifier(rte->alias->aliasname));
 
 	/*
 	 * Add the insert-column-names list.  To handle indirection properly, we
@@ -5479,13 +5483,38 @@ get_insert_query_def(Query *query, deparse_context *context)
 	{
 		OnConflictExpr *confl = query->onConflict;
 
+		appendStringInfo(buf, " ON CONFLICT");
+
+		if (confl->arbiterElems)
+		{
+			/* Add the single-VALUES expression list */
+			appendStringInfoChar(buf, '(');
+			get_rule_expr((Node *) confl->arbiterElems, context, false);
+			appendStringInfoChar(buf, ')');
+
+			/* Add a WHERE clause (for partial indexes) if given */
+			if (confl->arbiterWhere != NULL)
+			{
+				appendContextKeyword(context, " WHERE ",
+									 -PRETTYINDENT_STD, PRETTYINDENT_STD, 1);
+				get_rule_expr(confl->arbiterWhere, context, false);
+			}
+		}
+		else
+		{
+			char   *constraint = get_constraint_name(confl->constraint);
+
+			appendStringInfo(buf, " ON CONSTRAINT %s",
+							 quote_qualified_identifier(NULL, constraint));
+		}
+
 		if (confl->action == ONCONFLICT_NOTHING)
 		{
-			appendStringInfoString(buf, " ON CONFLICT DO NOTHING");
+			appendStringInfoString(buf, " DO NOTHING");
 		}
 		else
 		{
-			appendStringInfoString(buf, " ON CONFLICT DO UPDATE SET ");
+			appendStringInfoString(buf, " DO UPDATE SET ");
 			/* Deparse targetlist */
 			get_update_query_targetlist_def(query, confl->onConflictSet,
 											context, rte);
@@ -7886,6 +7915,52 @@ get_rule_expr(Node *node, deparse_context *context,
 			}
 			break;
 
+		case T_InferenceElem:
+			{
+				InferenceElem  *iexpr = (InferenceElem *) node;
+				bool			varprefix = context->varprefix;
+				bool			need_parens;
+
+				/*
+				 * InferenceElem can only refer to target relation, so a
+				 * prefix is never useful.
+				 */
+				context->varprefix = false;
+
+				/*
+				 * Parenthesize the element unless it's a simple Var or a bare
+				 * function call.  Follows pg_get_indexdef_worker().
+				 */
+				need_parens = !IsA(iexpr->expr, Var);
+				if (IsA(iexpr->expr, FuncExpr) &&
+					((FuncExpr *) iexpr->expr)->funcformat ==
+					COERCE_EXPLICIT_CALL)
+					need_parens = false;
+
+				if (need_parens)
+					appendStringInfoChar(buf, '(');
+				get_rule_expr((Node *) iexpr->expr,
+							  context, false);
+				if (need_parens)
+					appendStringInfoChar(buf, ')');
+
+				context->varprefix = varprefix;
+
+				if (iexpr->infercollid)
+					appendStringInfo(buf, " COLLATE %s",
+									 generate_collation_name(iexpr->infercollid));
+
+				/* Add the operator class name, if not default */
+				if (iexpr->inferopclass)
+				{
+					Oid		inferopclass = iexpr->inferopclass;
+					Oid		inferopcinputtype = get_opclass_input_type(iexpr->inferopclass);
+
+					get_opclass_name(inferopclass, inferopcinputtype, buf);
+				}
+			}
+			break;
+
 		case T_List:
 			{
 				char	   *sep;

src/test/regress/expected/insert_conflict.out

@@ -208,7 +208,7 @@ insert into insertconflicttest values (1, 'Apple') on conflict do update set fru
 ERROR:  ON CONFLICT DO UPDATE requires inference specification or constraint name
 LINE 1: ...nsert into insertconflicttest values (1, 'Apple') on conflic...
                                                              ^
-HINT:  For example, ON CONFLICT ON CONFLICT (<column>).
+HINT:  For example, ON CONFLICT (<column>).
 -- inference succeeds:
 insert into insertconflicttest values (1, 'Apple') on conflict (key) do update set fruit = excluded.fruit;
 insert into insertconflicttest values (2, 'Orange') on conflict (key, key, key) do update set fruit = excluded.fruit;

src/test/regress/expected/rules.out

@@ -2676,6 +2676,34 @@ Rules:
     ON DELETE TO rules_src DO
  NOTIFY rules_src_deletion
 
+--
+-- Ensure a aliased target relation for insert is correctly deparsed.
+--
+create rule r4 as on insert to rules_src do instead insert into rules_log AS trgt SELECT NEW.* RETURNING trgt.f1, trgt.f2;
+create rule r5 as on update to rules_src do instead UPDATE rules_log AS trgt SET tag = 'updated' WHERE trgt.f1 = new.f1;
+\d+ rules_src
+                      Table "public.rules_src"
+ Column |  Type   | Modifiers | Storage | Stats target | Description 
+--------+---------+-----------+---------+--------------+-------------
+ f1     | integer |           | plain   |              | 
+ f2     | integer |           | plain   |              | 
+Rules:
+    r1 AS
+    ON UPDATE TO rules_src DO  INSERT INTO rules_log (f1, f2, tag) VALUES (old.f1,old.f2,'old'::text), (new.f1,new.f2,'new'::text)
+    r2 AS
+    ON UPDATE TO rules_src DO  VALUES (old.f1,old.f2,'old'::text), (new.f1,new.f2,'new'::text)
+    r3 AS
+    ON DELETE TO rules_src DO
+ NOTIFY rules_src_deletion
+    r4 AS
+    ON INSERT TO rules_src DO INSTEAD  INSERT INTO rules_log AS trgt (f1, f2)  SELECT new.f1,
+            new.f2
+  RETURNING trgt.f1,
+    trgt.f2
+    r5 AS
+    ON UPDATE TO rules_src DO INSTEAD  UPDATE rules_log trgt SET tag = 'updated'::text
+  WHERE trgt.f1 = new.f1
+
 --
 -- check alter rename rule
 --
@@ -2778,16 +2806,19 @@ CREATE TABLE hats (
 	hat_color   char(10)      -- hat color
 );
 CREATE TABLE hat_data (
-	hat_name    char(10) primary key,
+	hat_name    char(10),
 	hat_color   char(10)      -- hat color
 );
+create unique index hat_data_unique_idx
+  on hat_data (hat_name COLLATE "C" bpchar_pattern_ops);
 -- okay
 CREATE RULE hat_nosert AS ON INSERT TO hats
     DO INSTEAD
     INSERT INTO hat_data VALUES (
            NEW.hat_name,
            NEW.hat_color)
-        ON CONFLICT (hat_name) DO NOTHING RETURNING *;
+        ON CONFLICT (hat_name COLLATE "C" bpchar_pattern_ops) WHERE hat_color = 'green'
+        DO NOTHING RETURNING *;
 -- Works (projects row)
 INSERT INTO hats VALUES ('h7', 'black') RETURNING *;
   hat_name  | hat_color  
@@ -2803,12 +2834,13 @@ INSERT INTO hats VALUES ('h7', 'black') RETURNING *;
 
 SELECT tablename, rulename, definition FROM pg_rules
 	WHERE tablename = 'hats';
- tablename |  rulename  |                                  definition                                  
------------+------------+------------------------------------------------------------------------------
- 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 DO NOTHING               +
-           |            |   RETURNING hat_data.hat_name,                                              +
+ tablename |  rulename  |                                         definition                                          
+-----------+------------+---------------------------------------------------------------------------------------------
+ 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                                  +
+           |            |   RETURNING hat_data.hat_name,                                                             +
            |            |     hat_data.hat_color;
 (1 row)
 
@@ -2861,13 +2893,13 @@ SELECT * FROM hat_data WHERE hat_name = 'h8';
 
 SELECT tablename, rulename, definition FROM pg_rules
 	WHERE tablename = 'hats';
- tablename |  rulename  |                                                          definition                                                           
------------+------------+-------------------------------------------------------------------------------------------------------------------------------
- hats      | hat_upsert | CREATE RULE hat_upsert AS                                                                                                    +
-           |            |     ON INSERT TO hats DO INSTEAD  INSERT INTO hat_data (hat_name, hat_color)                                                 +
-           |            |   VALUES (new.hat_name, new.hat_color) ON CONFLICT DO UPDATE SET hat_name = hat_data.hat_name, hat_color = excluded.hat_color+
-           |            |   WHERE (excluded.hat_color <> 'forbidden'::bpchar)                                                                          +
-           |            |   RETURNING hat_data.hat_name,                                                                                               +
+ tablename |  rulename  |                                                               definition                                                                
+-----------+------------+-----------------------------------------------------------------------------------------------------------------------------------------
+ hats      | hat_upsert | CREATE RULE hat_upsert 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) DO UPDATE SET hat_name = hat_data.hat_name, hat_color = excluded.hat_color+
+           |            |   WHERE (excluded.hat_color <> 'forbidden'::bpchar)                                                                                    +
+           |            |   RETURNING hat_data.hat_name,                                                                                                         +
            |            |     hat_data.hat_color;
 (1 row)
 
@@ -2877,7 +2909,7 @@ explain (costs off) INSERT INTO hats VALUES ('h8', 'forbidden') RETURNING *;
 ----------------------------------------------------------------
  Insert on hat_data
    Conflict Resolution: UPDATE
-   Conflict Arbiter Indexes: hat_data_pkey
+   Conflict Arbiter Indexes: hat_data_unique_idx
    Conflict Filter: (excluded.hat_color <> 'forbidden'::bpchar)
    ->  Result
 (5 rows)
@@ -2909,7 +2941,7 @@ RETURNING *;
 ----------------------------------------------------------------
  Insert on hat_data
    Conflict Resolution: UPDATE
-   Conflict Arbiter Indexes: hat_data_pkey
+   Conflict Arbiter Indexes: hat_data_unique_idx
    Conflict Filter: (excluded.hat_color <> 'forbidden'::bpchar)
    CTE data
      ->  Values Scan on "*VALUES*"

src/test/regress/sql/rules.sql

@@ -996,6 +996,13 @@ select * from rules_log;
 create rule r3 as on delete to rules_src do notify rules_src_deletion;
 \d+ rules_src
 
+--
+-- Ensure a aliased target relation for insert is correctly deparsed.
+--
+create rule r4 as on insert to rules_src do instead insert into rules_log AS trgt SELECT NEW.* RETURNING trgt.f1, trgt.f2;
+create rule r5 as on update to rules_src do instead UPDATE rules_log AS trgt SET tag = 'updated' WHERE trgt.f1 = new.f1;
+\d+ rules_src
+
 --
 -- check alter rename rule
 --
@@ -1049,9 +1056,11 @@ CREATE TABLE hats (
 );
 
 CREATE TABLE hat_data (
-	hat_name    char(10) primary key,
+	hat_name    char(10),
 	hat_color   char(10)      -- hat color
 );
+create unique index hat_data_unique_idx
+  on hat_data (hat_name COLLATE "C" bpchar_pattern_ops);
 
 -- okay
 CREATE RULE hat_nosert AS ON INSERT TO hats
@@ -1059,7 +1068,8 @@ CREATE RULE hat_nosert AS ON INSERT TO hats
     INSERT INTO hat_data VALUES (
            NEW.hat_name,
            NEW.hat_color)
-        ON CONFLICT (hat_name) DO NOTHING RETURNING *;
+        ON CONFLICT (hat_name COLLATE "C" bpchar_pattern_ops) WHERE hat_color = 'green'
+        DO NOTHING RETURNING *;
 
 -- Works (projects row)
 INSERT INTO hats VALUES ('h7', 'black') RETURNING *;