PostgreSQLにJDBC接続してfetchSizeを指定してselectするサンプル

PgFetchSize.kt

package kazusato.dbwork

import java.sql.DriverManager

/**
 * This program may be tested with -Xms48m -Xmx48m.
 * If fetchSize is not successfully enabled, OutOfMemoryError will occur.
 */
fun main() {
    DriverManager.getConnection("jdbc:postgresql://localhost/mydb", "myuser", "mypassword").use { pgConn ->
        pgConn.autoCommit = false // fetchSize doesn't work if autoCommit is not disabled
        pgConn.prepareStatement(
            "select aaa, bbb, ccc, ddd, eee from abc_def"
        ).use { pgPs ->
            pgPs.fetchSize = 10 // set fetch size
            pgPs.executeQuery().use { pgRs ->
                while (pgRs.next()) {
                    println(pgRs.getString(1))
                    println(pgRs.getString(2))
                    println(pgRs.getString(3))
                    println(pgRs.getString(4))
                    println(pgRs.getString(5))
                }
            }
        }
    }
}