>From: Tom Lane [mailto:t...@sss.pgh.pa.us] >> 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
Thank you very much Tom. PQfmode returns the correct value when using a type cast, so it solves my current problem. Perhaps you will implement the exact column size for querries with character functions somwhere in the future. It is a nice feature, which is implemented by Oracle or MS SQL Server. Do not know about MySQL. Regards, Bozena Potempa -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
