security-admin/db/postgres/patches/029-add-unique-constraint-on-table-x_group.sql

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--     http://www.apache.org/licenses/LICENSE-2.0
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select 'delimiter start';
CREATE OR REPLACE FUNCTION create_unique_constraint_on_username()
RETURNS void AS $$
DECLARE
 v_attnum integer := 0;
gu_attnum integer := 0;
BEGIN
 select attnum into v_attnum from pg_attribute where attrelid in(select oid from pg_class where relname='x_group') and attname='group_name';
 IF v_attnum > 0 THEN
        IF not exists (select * from pg_constraint where conrelid in(select oid from pg_class where relname='x_group') and conname='x_group_uk_group_name' and contype='u') THEN
                IF not exists (select * from pg_index where indrelid in(select oid from pg_class where relname='x_group') and indkey[0]=v_attnum) THEN
                        ALTER TABLE x_group ALTER COLUMN group_name TYPE VARCHAR(767),ADD CONSTRAINT x_group_UK_group_name UNIQUE(group_name);
                END IF;
        END IF;
 END IF;

select attnum into gu_attnum from pg_attribute where attrelid in(select oid from pg_class where relname='x_group_users') and attname='group_name';
 IF gu_attnum > 0 THEN
        IF not exists (select * from pg_constraint where conrelid in(select oid from pg_class where relname='x_group_users') and conname='x_group_users_UK_uid_gname' and contype='u') THEN
                IF not exists (select * from pg_index where indrelid in(select oid from pg_class where relname='x_group_users') and indkey[0]=gu_attnum) THEN
                        ALTER TABLE x_group_users ALTER COLUMN group_name TYPE VARCHAR(767),ADD CONSTRAINT x_group_users_UK_uid_gname UNIQUE(user_id,group_name);
                END IF;
        END IF;
 END IF;

END;
$$ LANGUAGE plpgsql;
select create_unique_constraint_on_username();
select 'delimiter end';