Re: remove indexes on a column?

"Vance Maverick" <vmaverick(at)pgp(dot)com> writes:
> I'd like to write a SQL script, possibly with some PL/pgSQL, that can
> find all indexes on a column -- so I can remove them, and set up
> exactly the indexes I want.

Yeah, this seems a bit tricky if you have expression indexes involving
the column. I concur that trying to parse the expressions is a bad
idea --- even if your code works today, it'll probably break in future
PG releases, because the nodetree representation is not very stable.

What I'd look for is pg_depend entries showing indexes that depend on
the column. Here's a hint:

regression=# create table foo (f1 int);
CREATE TABLE
regression=# create index fooi on foo (abs(f1));
CREATE INDEX
regression=# select * from pg_depend where refobjid = 'foo'::regclass;
classid | objid | objsubid | refclassid | refobjid | refobjsubid | deptype
---------+--------+----------+------------+----------+-------------+---------
1247 | 534605 | 0 | 1259 | 534603 | 0 | i
1259 | 534606 | 0 | 1259 | 534603 | 1 | a
(2 rows)

regression=# select 534606::regclass;
regclass
----------
fooi
(1 row)

regards, tom lane