PostgreSQL: Select data with a like on timestamp field

Try this:

SELECT my_table.id
FROM my_table
WHERE CAST(my_table.date_checker AS VARCHAR) LIKE '2011-01-%';

It's all very well not "wanting to use" < and > with timestamps, but those operators can be converted into index scans, and a string-match... well, it can, but EWWWW.

Well, the error is occurring because you need to explicitly convert the timestamp to a string before using a string operation on it, e.g.:

date_checker::text LIKE '2011-01-%'

and I suppose you could then create an index on (date_checker::text) and that expression would become an index scan but.... EWWWW.

Perhaps the date_trunc function would be more to your liking:

... WHERE date_trunc('month', my_table.date_checker) = '2011-01-01'

You can also put an index on that expression, if needed.