ERROR: failed to find conversion function from "unknown" to text

Q1: select '' union all select ''
Q2: select '' union all select * from (select '' ) as s

version: PostgreSQL 8.3.1, compiled by Visual C++ build 1400

Hi All,

    Q1 works just fine, but Q2 fails with:

ERROR:  failed to find conversion function from "unknown" to text

    Q2 is a generalization of a huge query we are facing, which we cannot modify. I don't think this is a 'removed-casts' problem generally faced in 8.3, but I may be wrong. Will adding some cast resolve this?

Best regards,
--
gurjeet[.singh]@EnterpriseDB.com
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