Hi,
When creating a constraint from table A to table B, the table name and column name in information_schema.constraint_column_usage shows table B. That makes impossible to check whether a constraint exists as we can have a constraint from table C to B and they will have same value in information_schema.constraint_column_usage.
Should we make the table_name and column_name as A's name?
=# create table item(id integer, item_name character VARYING(64),cat_id integer);
CREATE TABLE
=# create table catagory(id integer, cat_name character VARYING(64),CONSTRAINT catagory_pkey PRIMARY KEY (id) );
CREATE TABLE
=# alter table item add constraint fk_cat_id FOREIGN KEY (cat_id) REFERENCES catagory(id);
ALTER TABLE
=# select * from information_schema.constraint_column_usage where constraint_name='fk_cat_id';
table_catalog | table_schema | table_name | column_name | constraint_catalog | constraint_schema | constraint_name
---------------+--------------+------------+-------------+--------------------+-------------------+-----------------
vretrieve | public | catagory | id | vretrieve | public | fk_cat_id
(1 row)
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