Check if postgresql database exists (case insensitive way)
You can use:

SELECT datname FROM pg_catalog.pg_database WHERE lower(datname) = lower('dbname');


... however, database names are case sensitive, so attempting to connect to the DB name won't actually work unless you match the case correctly. This won't use any indexes on dbname, but it's rather unlikely that you'd have enough databases for this to matter.

Folks don't realize that because PostgreSQL case-folds unquoted identifiers to lower-case, so most of the time it looks case-insensitive for clients. In fact, "DatabaseName" and "databasename" are different things.