Will jvm die or not without pagination?

Question

Java

PreparedStatement ps = db.preparedStatement("select * from tbl");
ResultSet rs = ps.executeQuery();
while(rs.next) {
 ...
    process(...);
...
}

will jvm die if there are over 1,000,000,000 lines in tbl? Or does it subtract line by line from the base?

Answer 1

zhdbts-shnye rezaltsets read records by the cursor line by line. if you don't store what you get in memory inside your process, then the fetch size can be arbitrarily large.

Answer 2

It depends on what you have in the lines, what resources the host has, what garbage collector is used, how the JVM is configured, etc. etc. There are Java programs that work with terabyte heaps.

Answer 3

It all depends on the specific situation (which database, the driver used, the amount of data).
The last time I processed a large table, I initialized statement like this:

PreparedStatement preparedStatement = connection.prepareStatement(query,
                ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY);
        preparedStatement.setFetchSize(fetchSize);