Re: List of Index Columns & Expressions

On Jan 10, 2013, at 2:16 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

>> Is there some way to only get the relevant index expression from indexprs, rather than the whole expression?
>
> pg_get_indexdef() is your friend. You really, really don't want to
> write any client-side code that inspects indexprs directly. It'll
> break.

Ah-hah, somehow I missed that. So this:

SELECT s.i, pg_catalog.pg_get_indexdef( ci.oid, s.i+1, false)
FROM pg_catalog.pg_index x
JOIN pg_catalog.pg_class ct ON ct.oid = x.indrelid
JOIN pg_catalog.pg_class ci ON ci.oid = x.indexrelid
JOIN pg_catalog.pg_namespace n ON n.oid = ct.relnamespace
JOIN generate_series(0, current_setting('max_index_keys')::int - 1) s(i)
ON x.indkey[s.i] IS NOT NULL
WHERE ct.relname = 'foo'
AND ci.relname = 'idx_foo_stuff'
AND n.nspname = 'public'
ORDER BY s.i

Returns:

i | pg_get_indexdef
---+-----------------
0 | id
1 | abs(id)
2 | (bar_ids[1])

Which is perfect. Thanks!

David