Re: JDBC 9.2: multiple execution of prepared statement-query delivers different double precision results via getString()

The first few times the driver requests the server to return "1 as double precision" as a text value (thus using server side toString function).

After that the driver evaluates the actual types of the columns and requests the server to send the value in binary format. Your toString method will then invoke Double(1).toString on your client side.

If you modify your code to do
System.out.println("Value: " + rs.getDouble(1));
the result should not change as statements change column values to binary data encoding.

I do not think the driver can make guarantees about the format of getString values, unless the original database field is textual.

-Mikko
________________________________________
From: pgsql-jdbc-owner(at)postgresql(dot)org <pgsql-jdbc-owner(at)postgresql(dot)org> on behalf of Tilman Sandig <info(at)sandig(dot)com>
Sent: 13 September 2013 18:44
To: pgsql-jdbc(at)postgresql(dot)org
Subject: [JDBC] JDBC 9.2: multiple execution of prepared statement-query delivers different double precision results via getString()

Hello,

there might be a problem in the latest JDBC-driver (9.2 build 1003) when querying double precision-result columns multiple times
and retrieving the result with ResultSet.getString():

The first five queries work as expected, further calls append ".0" to the result-string.

Here is a sample code:

PreparedStatement stmt = myConnection.prepareStatement("select cast(1 as double precision)");
for (int x=0;x<12;x++){
ResultSet rs = stmt.executeQuery();
while (rs.next()){
System.out.println("Value: " + rs.getString(1));
}
}

-------
Output:
-------

Value: 1
Value: 1
Value: 1
Value: 1
Value: 1
Value: 1.0
Value: 1.0
Value: 1.0
Value: 1.0
Value: 1.0
Value: 1.0
Value: 1.0

The problem does not occur when using JDBC-driver version 9.1;
I use PostgreSQL Version 9.3.0 (Win64/Vista)

Best regards,
Tilman Sandig

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