How to Optimize PreparedStatement Reusage for Multiple Iterations?

Reusing a PreparedStatement with Multiple Iterations

In cases where a single, common connection is employed without a connection pool, you may encounter the question of whether it is more efficient to create a new PreparedStatement instance for each DML or SQL operation while preserving the benefits of prepared statements.

Instead of:

<code class="java">for (int i=0; i<1000; i++) {
    PreparedStatement preparedStatement = connection.prepareStatement(sql);
    preparedStatement.setObject(1, someValue);
    preparedStatement.executeQuery();
    preparedStatement.close();
}

You may consider:

<code class="java">PreparedStatement preparedStatement = connection.prepareStatement(sql);
for (int i=0; i<1000; i++) {
    preparedStatement.clearParameters();
    preparedStatement.setObject(1, someValue);
    preparedStatement.executeQuery();
}
preparedStatement.close();

While the second approach offers a slight efficiency gain, a superior solution lies in batch execution:

<code class="java">public void executeBatch(List<Entity> entities) throws SQLException { 
    try (
        Connection connection = dataSource.getConnection();
        PreparedStatement statement = connection.prepareStatement(SQL);
    ) {
        for (Entity entity : entities) {
            statement.setObject(1, entity.getSomeProperty());
            // ...

            statement.addBatch();
        }

        statement.executeBatch();
    }
}</code>

This approach takes advantage of batching capabilities provided by JDBC drivers, reducing the number of round-trips to the database and increasing efficiency. You can further optimize by defining a batch size limit, such as executing every 1000 items:

<code class="java">public void executeBatch(List<Entity> entities) throws SQLException { 
    try (
        Connection connection = dataSource.getConnection();
        PreparedStatement statement = connection.prepareStatement(SQL);
    ) {
        int i = 0;

        for (Entity entity : entities) {
            statement.setObject(1, entity.getSomeProperty());
            // ...

            statement.addBatch();
            i++;

            if (i % 1000 == 0 || i == entities.size()) {
                statement.executeBatch(); // Execute every 1000 items.
            }
        }
    }
}</code>

As for multithreaded environments, you can ensure thread safety by acquiring and closing both the connection and the statement within the shortest possible scope using the try-with-resources statement, as demonstrated in the code snippets above. For transactional batches, disable autocommit and commit the transaction only after all batches have completed.

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