ResultSet.isBeforeFirst returns true if result set is empty

[gabrieleciech]

I have recently upgraded my driver from jaybird 4.0.9 to 5.0.4 and I found a different behaviour for the ResultSet.isBeforeFirst method call when the result set is empty.

In version 4.0.9 the method correctly returns false if the query has no rows in the result set, instead in version 5.0.4 it returns true. In this way we no longer have the possibility of understanding whether a result set is empty or not.

It seems that this change was made while developing support for server-side scrolling in #693, by changing the initialization value of the variable isBeforeFirst in FbStatementFetcher

As a test query you can use:

SELECT 1 as myvar 
FROM rdb$database 
WHERE 1=0

and you get a different result executing the following code by changing the driver

var conn = DriverManager.getConnection(url, user, pass);
var stmt = conn.createStatement();
var query = "SELECT 1 as myvar FROM rdb$database WHERE 1=0"

ResultSet rs = stmt.executeQuery(strSQL);
if(!rs.isBeforeFirst()) {
    System.out.println("Result set is empty");
} else {
    System.out.println("Result set with records");
}

[mrotteveel]

Thanks for reporting. I'll need to double check why I changed this. I guess I did it for consistency with the scrollable fetch, but the JDBC specification indeed says it should report false when the result set is empty.

[mrotteveel]

To be front-ported to Jaybird 6 as well.

[mrotteveel]

The value of isAfterLast() also incorrectly reported true for an empty result set after calling next()

[mrotteveel]

Behaviour in Jaybird 4 was inconsistent and depended on the result set type and concurrency.