Clarify a foreign key error message

Clarify the message about type mismatch in foreign key definition to
indicate which column the referencing and which is the referenced one.

Reported-by: Jian He <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/CACJufxEL82ao-aXOa=d_-Xip0bix-qdSyNc9fcWxOdkEZFko8w@mail.gmail.com

Author: petere

src/backend/commands/tablecmds.c

@@ -9961,7 +9961,7 @@ ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 					(errcode(ERRCODE_DATATYPE_MISMATCH),
 					 errmsg("foreign key constraint \"%s\" cannot be implemented",
 							fkconstraint->conname),
-					 errdetail("Key columns \"%s\" and \"%s\" "
+					 errdetail("Key columns \"%s\" of the referencing table and \"%s\" of the referenced table "
 							   "are of incompatible types: %s and %s.",
 							   strVal(list_nth(fkconstraint->fk_attrs, i)),
 							   strVal(list_nth(fkconstraint->pk_attrs, i)),

src/test/regress/expected/alter_table.out

@@ -659,12 +659,12 @@ CREATE TEMP TABLE FKTABLE (ftest1 inet);
 -- This next should fail, because int=inet does not exist
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1) references pktable;
 ERROR:  foreign key constraint "fktable_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 -- This should also fail for the same reason, but here we
 -- give the column name
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1) references pktable(ptest1);
 ERROR:  foreign key constraint "fktable_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 DROP TABLE FKTABLE;
 -- This should succeed, even though they are different types,
 -- because int=int8 exists and is a member of the integer opfamily
@@ -682,7 +682,7 @@ DROP TABLE FKTABLE;
 CREATE TEMP TABLE FKTABLE (ftest1 numeric);
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1) references pktable;
 ERROR:  foreign key constraint "fktable_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: numeric and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: numeric and integer.
 DROP TABLE FKTABLE;
 DROP TABLE PKTABLE;
 -- On the other hand, this should work because int implicitly promotes to
@@ -704,26 +704,26 @@ CREATE TEMP TABLE PKTABLE (ptest1 int, ptest2 inet,
 CREATE TEMP TABLE FKTABLE (ftest1 cidr, ftest2 timestamp);
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1, ftest2) references pktable;
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: cidr and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: cidr and integer.
 DROP TABLE FKTABLE;
 -- Again, so should this...
 CREATE TEMP TABLE FKTABLE (ftest1 cidr, ftest2 timestamp);
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1, ftest2)
      references pktable(ptest1, ptest2);
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: cidr and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: cidr and integer.
 DROP TABLE FKTABLE;
 -- This fails because we mixed up the column ordering
 CREATE TEMP TABLE FKTABLE (ftest1 int, ftest2 inet);
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1, ftest2)
      references pktable(ptest2, ptest1);
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest2" are of incompatible types: integer and inet.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest2" of the referenced table are of incompatible types: integer and inet.
 -- As does this...
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest2, ftest1)
      references pktable(ptest1, ptest2);
 ERROR:  foreign key constraint "fktable_ftest2_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest2" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest2" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 DROP TABLE FKTABLE;
 DROP TABLE PKTABLE;
 -- Test that ALTER CONSTRAINT updates trigger deferrability properly
@@ -3458,7 +3458,7 @@ COMMENT ON CONSTRAINT comment_test_child_fk ON comment_test_child IS 'FOREIGN KE
 ALTER TABLE comment_test ALTER COLUMN id SET DATA TYPE text;
 ALTER TABLE comment_test ALTER COLUMN id SET DATA TYPE int USING id::integer;
 ERROR:  foreign key constraint "comment_test_child_fk" cannot be implemented
-DETAIL:  Key columns "id" and "id" are of incompatible types: text and integer.
+DETAIL:  Key columns "id" of the referencing table and "id" of the referenced table are of incompatible types: text and integer.
 -- Comments should be intact
 SELECT col_description('comment_test_child'::regclass, 1) as comment;
               comment              

src/test/regress/expected/enum.out

@@ -581,7 +581,7 @@ DETAIL:  Key (id)=(red) is still referenced from table "enumtest_child".
 CREATE TYPE bogus AS ENUM('good', 'bad', 'ugly');
 CREATE TABLE enumtest_bogus_child(parent bogus REFERENCES enumtest_parent);
 ERROR:  foreign key constraint "enumtest_bogus_child_parent_fkey" cannot be implemented
-DETAIL:  Key columns "parent" and "id" are of incompatible types: bogus and rainbow.
+DETAIL:  Key columns "parent" of the referencing table and "id" of the referenced table are of incompatible types: bogus and rainbow.
 DROP TYPE bogus;
 -- check renaming a value
 ALTER TYPE rainbow RENAME VALUE 'red' TO 'crimson';

src/test/regress/expected/foreign_key.out

@@ -822,12 +822,12 @@ INSERT INTO PKTABLE VALUES(42);
 -- This next should fail, because int=inet does not exist
 CREATE TABLE FKTABLE (ftest1 inet REFERENCES pktable);
 ERROR:  foreign key constraint "fktable_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 -- This should also fail for the same reason, but here we
 -- give the column name
 CREATE TABLE FKTABLE (ftest1 inet REFERENCES pktable(ptest1));
 ERROR:  foreign key constraint "fktable_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 -- This should succeed, even though they are different types,
 -- because int=int8 exists and is a member of the integer opfamily
 CREATE TABLE FKTABLE (ftest1 int8 REFERENCES pktable);
@@ -846,7 +846,7 @@ DROP TABLE FKTABLE;
 -- of the integer opfamily)
 CREATE TABLE FKTABLE (ftest1 numeric REFERENCES pktable);
 ERROR:  foreign key constraint "fktable_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: numeric and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: numeric and integer.
 DROP TABLE PKTABLE;
 -- On the other hand, this should work because int implicitly promotes to
 -- numeric, and we allow promotion on the FK side
@@ -869,23 +869,23 @@ CREATE TABLE PKTABLE (ptest1 int, ptest2 inet, PRIMARY KEY(ptest1, ptest2));
 -- This should fail, because we just chose really odd types
 CREATE TABLE FKTABLE (ftest1 cidr, ftest2 timestamp, FOREIGN KEY(ftest1, ftest2) REFERENCES pktable);
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: cidr and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: cidr and integer.
 -- Again, so should this...
 CREATE TABLE FKTABLE (ftest1 cidr, ftest2 timestamp, FOREIGN KEY(ftest1, ftest2) REFERENCES pktable(ptest1, ptest2));
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: cidr and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: cidr and integer.
 -- This fails because we mixed up the column ordering
 CREATE TABLE FKTABLE (ftest1 int, ftest2 inet, FOREIGN KEY(ftest2, ftest1) REFERENCES pktable);
 ERROR:  foreign key constraint "fktable_ftest2_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest2" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest2" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 -- As does this...
 CREATE TABLE FKTABLE (ftest1 int, ftest2 inet, FOREIGN KEY(ftest2, ftest1) REFERENCES pktable(ptest1, ptest2));
 ERROR:  foreign key constraint "fktable_ftest2_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest2" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest2" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 -- And again..
 CREATE TABLE FKTABLE (ftest1 int, ftest2 inet, FOREIGN KEY(ftest1, ftest2) REFERENCES pktable(ptest2, ptest1));
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest2" are of incompatible types: integer and inet.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest2" of the referenced table are of incompatible types: integer and inet.
 -- This works...
 CREATE TABLE FKTABLE (ftest1 int, ftest2 inet, FOREIGN KEY(ftest2, ftest1) REFERENCES pktable(ptest2, ptest1));
 DROP TABLE FKTABLE;
@@ -906,17 +906,17 @@ DROP TABLE PKTABLE;
 CREATE TABLE PKTABLE (ptest1 int, ptest2 inet, ptest3 int, ptest4 inet, PRIMARY KEY(ptest1, ptest2), FOREIGN KEY(ptest3,
 ptest4) REFERENCES pktable(ptest2, ptest1));
 ERROR:  foreign key constraint "pktable_ptest3_ptest4_fkey" cannot be implemented
-DETAIL:  Key columns "ptest3" and "ptest2" are of incompatible types: integer and inet.
+DETAIL:  Key columns "ptest3" of the referencing table and "ptest2" of the referenced table are of incompatible types: integer and inet.
 -- Nor should this... (same reason, we have 4,3 referencing 1,2 which mismatches types
 CREATE TABLE PKTABLE (ptest1 int, ptest2 inet, ptest3 int, ptest4 inet, PRIMARY KEY(ptest1, ptest2), FOREIGN KEY(ptest4,
 ptest3) REFERENCES pktable(ptest1, ptest2));
 ERROR:  foreign key constraint "pktable_ptest4_ptest3_fkey" cannot be implemented
-DETAIL:  Key columns "ptest4" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ptest4" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 -- Not this one either... Same as the last one except we didn't defined the columns being referenced.
 CREATE TABLE PKTABLE (ptest1 int, ptest2 inet, ptest3 int, ptest4 inet, PRIMARY KEY(ptest1, ptest2), FOREIGN KEY(ptest4,
 ptest3) REFERENCES pktable);
 ERROR:  foreign key constraint "pktable_ptest4_ptest3_fkey" cannot be implemented
-DETAIL:  Key columns "ptest4" and "ptest1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ptest4" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet and integer.
 --
 -- Now some cases with inheritance
 -- Basic 2 table case: 1 column of matching types.
@@ -1009,40 +1009,40 @@ create table pktable(ptest1 inet, primary key(base1, ptest1)) inherits (pktable_
 -- just generally bad types (with and without column references on the referenced table)
 create table fktable(ftest1 cidr, ftest2 int[], foreign key (ftest1, ftest2) references pktable);
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "base1" are of incompatible types: cidr and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "base1" of the referenced table are of incompatible types: cidr and integer.
 create table fktable(ftest1 cidr, ftest2 int[], foreign key (ftest1, ftest2) references pktable(base1, ptest1));
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "base1" are of incompatible types: cidr and integer.
+DETAIL:  Key columns "ftest1" of the referencing table and "base1" of the referenced table are of incompatible types: cidr and integer.
 -- let's mix up which columns reference which
 create table fktable(ftest1 int, ftest2 inet, foreign key(ftest2, ftest1) references pktable);
 ERROR:  foreign key constraint "fktable_ftest2_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest2" and "base1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest2" of the referencing table and "base1" of the referenced table are of incompatible types: inet and integer.
 create table fktable(ftest1 int, ftest2 inet, foreign key(ftest2, ftest1) references pktable(base1, ptest1));
 ERROR:  foreign key constraint "fktable_ftest2_ftest1_fkey" cannot be implemented
-DETAIL:  Key columns "ftest2" and "base1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ftest2" of the referencing table and "base1" of the referenced table are of incompatible types: inet and integer.
 create table fktable(ftest1 int, ftest2 inet, foreign key(ftest1, ftest2) references pktable(ptest1, base1));
 ERROR:  foreign key constraint "fktable_ftest1_ftest2_fkey" cannot be implemented
-DETAIL:  Key columns "ftest1" and "ptest1" are of incompatible types: integer and inet.
+DETAIL:  Key columns "ftest1" of the referencing table and "ptest1" of the referenced table are of incompatible types: integer and inet.
 drop table pktable;
 drop table pktable_base;
 -- 2 columns (1 table), mismatched types
 create table pktable_base(base1 int not null, base2 int);
 create table pktable(ptest1 inet, ptest2 inet[], primary key(base1, ptest1), foreign key(base2, ptest2) references
                                              pktable(base1, ptest1)) inherits (pktable_base);
 ERROR:  foreign key constraint "pktable_base2_ptest2_fkey" cannot be implemented
-DETAIL:  Key columns "ptest2" and "ptest1" are of incompatible types: inet[] and inet.
+DETAIL:  Key columns "ptest2" of the referencing table and "ptest1" of the referenced table are of incompatible types: inet[] and inet.
 create table pktable(ptest1 inet, ptest2 inet, primary key(base1, ptest1), foreign key(base2, ptest2) references
                                              pktable(ptest1, base1)) inherits (pktable_base);
 ERROR:  foreign key constraint "pktable_base2_ptest2_fkey" cannot be implemented
-DETAIL:  Key columns "base2" and "ptest1" are of incompatible types: integer and inet.
+DETAIL:  Key columns "base2" of the referencing table and "ptest1" of the referenced table are of incompatible types: integer and inet.
 create table pktable(ptest1 inet, ptest2 inet, primary key(base1, ptest1), foreign key(ptest2, base2) references
                                              pktable(base1, ptest1)) inherits (pktable_base);
 ERROR:  foreign key constraint "pktable_ptest2_base2_fkey" cannot be implemented
-DETAIL:  Key columns "ptest2" and "base1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ptest2" of the referencing table and "base1" of the referenced table are of incompatible types: inet and integer.
 create table pktable(ptest1 inet, ptest2 inet, primary key(base1, ptest1), foreign key(ptest2, base2) references
                                              pktable(base1, ptest1)) inherits (pktable_base);
 ERROR:  foreign key constraint "pktable_ptest2_base2_fkey" cannot be implemented
-DETAIL:  Key columns "ptest2" and "base1" are of incompatible types: inet and integer.
+DETAIL:  Key columns "ptest2" of the referencing table and "base1" of the referenced table are of incompatible types: inet and integer.
 drop table pktable;
 ERROR:  table "pktable" does not exist
 drop table pktable_base;
@@ -1154,22 +1154,22 @@ CREATE TEMP TABLE fktable (
 ALTER TABLE fktable ADD CONSTRAINT fk_2_3
 FOREIGN KEY (x2) REFERENCES pktable(id3);
 ERROR:  foreign key constraint "fk_2_3" cannot be implemented
-DETAIL:  Key columns "x2" and "id3" are of incompatible types: character varying and real.
+DETAIL:  Key columns "x2" of the referencing table and "id3" of the referenced table are of incompatible types: character varying and real.
 -- nor to int4
 ALTER TABLE fktable ADD CONSTRAINT fk_2_1
 FOREIGN KEY (x2) REFERENCES pktable(id1);
 ERROR:  foreign key constraint "fk_2_1" cannot be implemented
-DETAIL:  Key columns "x2" and "id1" are of incompatible types: character varying and integer.
+DETAIL:  Key columns "x2" of the referencing table and "id1" of the referenced table are of incompatible types: character varying and integer.
 -- real does not promote to int4
 ALTER TABLE fktable ADD CONSTRAINT fk_3_1
 FOREIGN KEY (x3) REFERENCES pktable(id1);
 ERROR:  foreign key constraint "fk_3_1" cannot be implemented
-DETAIL:  Key columns "x3" and "id1" are of incompatible types: real and integer.
+DETAIL:  Key columns "x3" of the referencing table and "id1" of the referenced table are of incompatible types: real and integer.
 -- int4 does not promote to text
 ALTER TABLE fktable ADD CONSTRAINT fk_1_2
 FOREIGN KEY (x1) REFERENCES pktable(id2);
 ERROR:  foreign key constraint "fk_1_2" cannot be implemented
-DETAIL:  Key columns "x1" and "id2" are of incompatible types: integer and character varying.
+DETAIL:  Key columns "x1" of the referencing table and "id2" of the referenced table are of incompatible types: integer and character varying.
 -- should succeed
 -- int4 promotes to real
 ALTER TABLE fktable ADD CONSTRAINT fk_1_3
@@ -1192,11 +1192,11 @@ FOREIGN KEY (x2,x5,x3) REFERENCES pktable(id2,id1,id3);
 ALTER TABLE fktable ADD CONSTRAINT fk_123_231
 FOREIGN KEY (x1,x2,x3) REFERENCES pktable(id2,id3,id1);
 ERROR:  foreign key constraint "fk_123_231" cannot be implemented
-DETAIL:  Key columns "x1" and "id2" are of incompatible types: integer and character varying.
+DETAIL:  Key columns "x1" of the referencing table and "id2" of the referenced table are of incompatible types: integer and character varying.
 ALTER TABLE fktable ADD CONSTRAINT fk_241_132
 FOREIGN KEY (x2,x4,x1) REFERENCES pktable(id1,id3,id2);
 ERROR:  foreign key constraint "fk_241_132" cannot be implemented
-DETAIL:  Key columns "x2" and "id1" are of incompatible types: character varying and integer.
+DETAIL:  Key columns "x2" of the referencing table and "id1" of the referenced table are of incompatible types: character varying and integer.
 DROP TABLE pktable, fktable;
 -- test a tricky case: we can elide firing the FK check trigger during
 -- an UPDATE if the UPDATE did not change the foreign key