Today I Learned

A Hashrocket project

Lower Is Faster Than ilike

There are a couple ways to do a case-insensitive comparison of data in PostgreSQL. One way is to use the ilike operator for comparison. Another way is to use the lower() function on both sides of the = operator for comparison. Using lower() is a bit faster than using ilike.

When comparing

select * from users where email ilike '';


select * from users where lower(email) = lower('');

we find (via explain analyze) that using lower() was taking around 12ms where as the ilike example was taking around 17ms.

We earn orders of magnitude in performance when adding a functional index that uses the lower() function like so:

create unique index users_unique_lower_email_idx on users (lower(email));

After adding this index, the example using lower() drops to around 0.08ms.

For the full example and explain analyze outputs, see this document.

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