When autoCommit=true, PostgreSQL JDBC driver ignores the fetch size which set with Statement#setFetchSize().

http://stackoverflow.com/questions/1468036/java-jdbc-ignores-setfetchsize
https://jdbc.postgresql.org/documentation/94/query.html#query-with-cursor

It seems like PostgreSQL specific but important to deal with large datasets. and we can't set it to false in connection URL with PostgreSQL JDBC driver. http://postgresql.nabble.com/Connection-Properties-for-FetchSize-and-Autocommit-td2175811.html

I think typically JdbcItemReader will be used with a non-jta data source which is autoCommit=true by default so it would insufficient to work with large datasets. so I wish JdbcItemReader to implement a batch property named autoCommit.

A workaround is that we can implement a subclass of JdbcItemReader and override getConnection() and invoke Connection#autoCommit(false) before returning it.