Sync FK behaviour when creating hypertable

We now allow FKs to hypertables but the initial check when creating
the hypertable was not adjusted so tables with pre-existing FKs
would not be allowed to be changed into hypertable while creating
the FK constraint afterwards succeeded.

.unreleased/pr_7301

@@ -0,0 +1 @@
+Fixes: #7301 Make foreign key behaviour for hypertables consistent

src/hypertable.c

@@ -1319,14 +1319,17 @@ hypertable_validate_constraints(Oid relid)
  {
  Form_pg_constraint form = (Form_pg_constraint) GETSTRUCT(tuple);
 
- if (form->contype == CONSTRAINT_FOREIGN)
- ereport(ERROR,
- (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
- errmsg("cannot have FOREIGN KEY constraints to hypertable \"%s\"",
- get_rel_name(relid)),
- errhint("Remove all FOREIGN KEY constraints to table \"%s\" before "
- "making it a hypertable.",
- get_rel_name(relid))));
+ /*
+ * Hypertable <-> hypertable foreign keys are not supported.
+ */
+ if (form->contype == CONSTRAINT_FOREIGN && ts_hypertable_relid_to_id(form->conrelid) != -1)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+ errmsg("cannot have FOREIGN KEY constraints to hypertable \"%s\"",
+ get_rel_name(relid)),
+ errhint("Remove all FOREIGN KEY constraints to table \"%s\" before "
+ "making it a hypertable.",
+ get_rel_name(relid))));
  }
 
  systable_endscan(scan);

test/sql/create_hypertable.sql

@@ -632,7 +632,6 @@ select * from tidrangescan_test where time > '2023-02-12 00:00:00+02:40'::timest
 
 drop table tidrangescan_test;
 
-\set ON_ERROR_STOP 0
 \set VERBOSITY default
 set client_min_messages = WARNING;
 -- test creating a hypertable from table referenced by a foreign key fails with
@@ -643,6 +642,8 @@ create table test_schema.fk_child(
  id int,
  foreign key (time, id) references test_schema.fk_parent(time, id)
 );
+select create_hypertable ('test_schema.fk_child', 'time');
+\set ON_ERROR_STOP 0
 select create_hypertable ('test_schema.fk_parent', 'time');
 \set ON_ERROR_STOP 1
 

tsl/test/expected/foreign_keys.out

@@ -1025,3 +1025,34 @@ SELECT create_hypertable('i7226', 'time');
 
 CREATE TABLE i7226_valid(time timestamptz NOT NULL,device_id int NOT NULL, FOREIGN KEY(time, device_id) REFERENCES i7226(time, device_id));
 INSERT INTO i7226 VALUES ('2024-08-29 12:00:00+00', 1);
+-- test foreign key constraints that have been created before hypertable conversion
+create table converted_pk(time timestamptz, id int, unique(time, id));
+create table converted_fk(time timestamptz, id int, foreign key (time, id) references converted_pk(time, id));
+select table_name FROM create_hypertable ('converted_pk', 'time');
+NOTICE: adding not-null constraint to column "time"
+ table_name 
+--------------
+ converted_pk
+(1 row)
+
+\set ON_ERROR_STOP 0
+-- should fail
+INSERT INTO converted_fk SELECT '2020-01-01', 1;
+ERROR: insert or update on table "converted_fk" violates foreign key constraint "converted_fk_time_id_fkey"
+\set ON_ERROR_STOP 1
+INSERT INTO converted_pk SELECT '2020-01-01 0:01', 1;
+\set ON_ERROR_STOP 0
+-- should still fail
+INSERT INTO converted_fk SELECT '2020-01-01', 1;
+ERROR: insert or update on table "converted_fk" violates foreign key constraint "converted_fk_time_id_fkey"
+\set ON_ERROR_STOP 1
+INSERT INTO converted_fk SELECT '2020-01-01 0:01', 1;
+\set ON_ERROR_STOP 0
+-- should fail
+DELETE FROM converted_pk WHERE time = '2020-01-01 0:01';
+ERROR: update or delete on table "_hyper_16_27_chunk" violates foreign key constraint "converted_fk_time_id_fkey1" on table "converted_fk"
+TRUNCATE converted_pk;
+ERROR: cannot truncate a table referenced in a foreign key constraint
+\set ON_ERROR_STOP 1
+DELETE FROM converted_fk;
+DELETE FROM converted_pk WHERE time = '2020-01-01 0:01';

tsl/test/sql/foreign_keys.sql

@@ -650,3 +650,31 @@ SELECT create_hypertable('i7226', 'time');
 CREATE TABLE i7226_valid(time timestamptz NOT NULL,device_id int NOT NULL, FOREIGN KEY(time, device_id) REFERENCES i7226(time, device_id));
 INSERT INTO i7226 VALUES ('2024-08-29 12:00:00+00', 1);
 
+-- test foreign key constraints that have been created before hypertable conversion
+create table converted_pk(time timestamptz, id int, unique(time, id));
+create table converted_fk(time timestamptz, id int, foreign key (time, id) references converted_pk(time, id));
+
+select table_name FROM create_hypertable ('converted_pk', 'time');
+
+\set ON_ERROR_STOP 0
+-- should fail
+INSERT INTO converted_fk SELECT '2020-01-01', 1;
+\set ON_ERROR_STOP 1
+
+INSERT INTO converted_pk SELECT '2020-01-01 0:01', 1;
+
+\set ON_ERROR_STOP 0
+-- should still fail
+INSERT INTO converted_fk SELECT '2020-01-01', 1;
+\set ON_ERROR_STOP 1
+INSERT INTO converted_fk SELECT '2020-01-01 0:01', 1;
+
+\set ON_ERROR_STOP 0
+-- should fail
+DELETE FROM converted_pk WHERE time = '2020-01-01 0:01';
+TRUNCATE converted_pk;
+\set ON_ERROR_STOP 1
+
+DELETE FROM converted_fk;
+DELETE FROM converted_pk WHERE time = '2020-01-01 0:01';
+