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How do I create an index in PostgreSQL based on lowercase only?

How would I set up an index based on lower case only?

Even though the actual field contains both upper and lower case letters.

Also, can I run a query and have only the lower case index value returned?

Solution

  • You can create the index and transform the field to upper- or lower-case. Then when you do your queries, you can do the same transform and it'll do the right thing.

    So:

    CREATE UNIQUE INDEX lower_case_username ON users ((lower(username)));

    Then query for the same thing:

    SELECT username FROM users WHERE lower(username) = 'bob';