BUG #16088: Multiple foreigh keys created on "ALTER TABLE" command
The following bug has been logged on the website:
Bug reference: 16088
Logged by: Jess Sturgeon
Email address: jsturgeon@novetta.com
PostgreSQL version: 12.0
Operating system: RHEL 7.7
Description:
If you run this command multiple times:
ALTER TABLE myschema.mytable ADD IF NOT EXISTS mycolumn uuid REFERENCES
myschema.mytable2(userid);
It adds the column once, but adds a duplicate FOREIGN KEY each time. I had
over 59 keys while debugging my schema definition :)
This happens in PG11.5 and PG12 for me, both on RHEL 7.7
PG Bug reporting form <noreply@postgresql.org> writes:
If you run this command multiple times:
ALTER TABLE myschema.mytable ADD IF NOT EXISTS mycolumn uuid REFERENCES
myschema.mytable2(userid);
It adds the column once, but adds a duplicate FOREIGN KEY each time.
Yeah, this is a well known problem :-(. The IF NOT EXISTS conditionalizes
addition of the column, but not the quasi-independent addition of the
foreign key constraint. There's work afoot to make this behave more
intuitively, but it won't land before v13 at the earliest.
regards, tom lane