Re: adding foreign key constraint locks up table

* Tom Lane:

>> Do you mean that the ALTER query and subsequent queries are shown as
>> "waiting" in pg_stat_activity?  In this case, I'm also wondering why
>> this is inecessary.
>
> ALTER ADD FOREIGN KEY must lock both tables to add triggers to them.

But why is such a broad lock needed?  If the table was created in the
current transaction and is empty, the contents of the foreign key
table should not matter.

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