Carefully removing unwanted indexes

Carefully removing? You mean press Enter gently after typing DROP INDEX? Err, no!

The thinking is that it takes a long time to build an index, and a short time to drop it. What we want is a way of removing an index such that if we discover that removing it was a mistake, we can put the index back again quickly.

Getting ready

The following query will list all invalid indexes, if any:

SELECT ir.relname AS indexname 
, it.relname AS tablename 
, n.nspname AS schemaname 
FROM pg_index i 
JOIN pg_class ir ON ir.oid = i.indexrelid 
JOIN pg_class it ON it.oid = i.indrelid 
JOIN pg_namespace n ON n.oid = it.relnamespace 
WHERE NOT i.indisvalid; 

Take note of these indexes, so that later you can tell whether a given index is invalid because we marked it as invalid during this recipe, in which case it can safely be marked as valid, or because it was already invalid for other reasons.

How to do it...

We will describe a procedure that allows us to deactivate an index without...