Fastest way to iterate through large table using JDBC

Question

I\'m trying to create a java program to cleanup and merge rows in my table. The table is large, about 500k rows and my current solution is running very slowly. The first thi

Answer 1

First of all, are you sure you need the whole table in memory? Maybe you should consider (if possible) selecting rows that you want to update/merge/etc. If you really have to have the whole table you could consider using a scrollable ResultSet. You can create it like this.

// make sure autocommit is off (postgres)
con.setAutoCommit(false);

Statement stmt = con.createStatement(
                   ResultSet.TYPE_SCROLL_INSENSITIVE, //or ResultSet.TYPE_FORWARD_ONLY
                   ResultSet.CONCUR_READ_ONLY);
ResultSet srs = stmt.executeQuery("select * from ...");

It enables you to move to any row you want by using 'absolute' and 'relative' methods.