Correct, and there is no need to create an index on a unique constraint or primary key as they are already implemented via indexes. I can’t count how many duplicate indexes I’ve dropped in the past. I use this view help find duplicates in a given system. Duplicate indexes just use up space and rob performance during updates and inserts.
/*======================================================================================================
q$Id: duplicate_index.sql 1 2015-12-19 15:40:29Z rui $
Description: Find duplicate indexes
======================================================================================================*/
create or replace view duplicate_index
as
select base.indrelid::regclass as table_name
, string_agg((dup.indexrelid::regclass)::text, E'\n') as indexes
, pg_size_pretty(avg(pg_relation_size(dup.indexrelid))) as avg_size
from pg_index base
join pg_index dup on dup.indrelid = base.indrelid -- table identifier
and dup.indkey = base.indkey -- columns indexed
and dup.indclass = base.indclass -- columns types
and (
dup.indexprs = base.indexprs -- expression predicate for columns
or (
dup.indexprs is null
and base.indexprs is null
)
)
and (
dup.indpred = base.indpred -- expression predicate for where clause
or (
dup.indpred is null
and base.indpred is null
)
)
and dup.indexrelid != base.indexrelid --index identifier
group by base.indrelid::regclass
, concat(base.indkey::text, base.indclass::text, base.indexprs, base.indpred)
order by avg_size desc
, base.indrelid::regclass
;
