Re: How to force Postgres to use index on ILIKE

>> SELECT toode, nimetus
>> FROM toode
>> WHERE toode ILIKE 'x10%' ESCAPE '!'
>> ORDER BY UPPER(toode ),nimetus LIMIT 100
>>
>> runs 1 minute in first time for small table size.
>>
>> Toode field type is CHAR(20)
>
> 1) why are you using CHAR and not VARCHAR or TEXT? CHAR will give you
> problems using an index, period.

1. I haven't seen any example where VARCHAR is better that CHAR for indexing
2. I have a lot of existing code. Changing CHAR to VARCHAR requires probably
re-writing a lot of code, a huge work.

> 2) You can't use an index on ILIKE.

I'ts very sad. I expected that lower(toode) index can be used.

> You can, however, use an index on
> lower(field) if your query is properly phrased and if you've created an
> expression index on lower(field).

I tried by Postgres does not use index. Why ?

create index nimib2 on firma1.klient(lower(nimi) bpchar_pattern_ops);

explain analyze select nimi from firma1.klient where lower(nimi) like
'mokter%'

"Seq Scan on klient (cost=0.00..9.79 rows=1 width=74) (actual
time=0.740..0.761 rows=1 loops=1)"
" Filter: (lower((nimi)::text) ~~ 'mokter%'::text)"
"Total runtime: 0.877 ms"