Multicolumn index for single-column queries?

[rihad <rihad@xxxxxxx>]

Hi. Say there are 2 indexes:

    "foo_index" btree (foo_id)

    "multi_index" btree (foo_id, approved, expires_at)


foo_id is an integer. Some queries involve all three columns in their WHERE clauses, some involve only foo_id.
Would it be ok from general performance standpoint to remove foo_index and rely only on multi_index? I know that
PG would have to do less work updating just one index compared to updating them both, but wouldn't searches
on foo_id alone become slower?

Thanks.