"Bozena Potempa" <bozena.pote...@otc.pl> writes: > Thank you. In this case (substring) there is no much to predict, just a > simple calculation, but I understand that it is a part of larger and more > complicated functionality. I tried to find a workaround with a type cast: > select substr(fc,1,2)::varchar(2) from test > Now the type returned is varchar, but the size is still -1. I think that it > is not a correct return: the size is specified explicitly in the query and > could be used by PQfsize.
Oh ... actually the problem there is that you have the wrong idea about what PQfsize means. What that returns is pg_type.typlen for the data type, which is always going to be -1 for a varlena type like varchar. The thing that you need to look at if you want to see information like the max length of a varchar is typmod (PQfmod). The typmod generally has some funny datatype-specific encoding; for varchar and char it works like this: -1: max length unknown or unspecified n>0: max length is n-4 characters regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers