Case sensitivity in PostgreSQL

PostgreSQL, unlike MySQL, treats strings as case sensitive in all circumstances.

This includes

• comparison with = and LIKE
• collision detection in unique indexes

Usually this is fine, but some strings (like emails and usernames) should typically be treated as case insensitive.

There are a few workarounds available:

• use the citext extension Show archive.org snapshot (not recommended)
• use ILIKE instead of LIKE
• use Postgres' lower() function
• add an index on lower(email)

Probably the best approach is to just convert emails (and usernames) to lowercase within Rails. Popular authentication libraries (like Clearance and Devise) already do this for you.