Re: failed to find conversion function from "unknown" to ...

Hi!

>select 1 where 'vasya' = (select 'vasya')
>produces
>ERROR: failed to find conversion function from "unknown" to text

I managed to find two similar messages
in GENERAL archive.

In first message
http://archives.postgresql.org/pgsql-general/2004-10/msg01368.php
Tom Lane says explicit cast is requiered
in second message
http://archives.postgresql.org/pgsql-sql/2005-01/msg00058.php
Tom Lane says it is a problem in PG.

These messages are about different things (first is
about View and second is about Case), though I don't
see difference between this situations and
don't have clear picture where (and what is the reason
behind this) I should explicitly
cast literals to text or varchar and where it is not
required.

Is this problem of string literals only or some other
types are involved?

Thanks.

--
Best regards
Ilja Golshtein