We have a PostgreSQL database with a fairly large table (~50 million rows). The table has a unique constraint across several columns, each of which is indexed. For context, I recently deleted about half the rows in the table -- old data. Now I want to simply remove the multi-column unique constraint, so I executed this SQL:
alter table my_big_table drop constraint my_constraint_name
However, I started the command 10+ hours ago, and it's still running with no sign of abating. Why would dropping a constraint be taking so long? Is there anything I'm missing, or any way to perform actions like this with some kind of progress or status indication?
(I'm using PostgreSQL 9.0 on a Windows 64-bit system, and I generally connect to it using pgAdmin, though I can use the command-line client or connect programmatically too.)