BUG #2729: Backslash escaping not working as expected

"Michael van Rooyen" <mvanr@bigfoot.com> writes:

The following query from psql:
select * from product where name like '%\\%';
Yields products whose names end with a %. I would have expected it to yeild
products whose names contained a backslash.

Postgres defaults to assuming \ as the LIKE escape character, that is,
what you typed is equivalent to

select * from product where name like '%\\%' escape '\\';

You can get the behavior you're expecting by not having any escape character:

select * from product where name like '%\\%' escape '';

This is as explained in TFM:
http://www.postgresql.org/docs/8.1/static/functions-matching.html#FUNCTIONS-LIKE
although I notice that SQL92 says that there is no escape character by
default. We can't change our historical documented behavior on the
point unless we were willing to provide a configuration variable to
adjust it, and I'm not sure it's worth that.

regards, tom lane