Spring Integration Jdbc OutboundGateway returning 1 record ONLY even with MaxRows(0) - spring-integration

Question

Have an application which has some 30,000+ records in a table and for an analytic use-case we need to fetch all and keep iterating over the returned result for some computation. However, the Jdbc OutboundGateway is returning ONLY 1 record even with MaxRows(0) though there are 30,000+ records in the DB. The same returns n number of records as a List when we explicitly set the MaxRows() with a non-zero value.
Please share how this can be made to return all rows with MaxRows(0)?

Answer 1

That's probably how your JDBC driver works or how your RDBMS is configured for maxRows.
The logic there in JdbcOutboundGateway is like this:
if (this.maxRows != null) {
Assert.notNull(this.poller, "If you want to set 'maxRows', then you must provide a 'selectQuery'.");
this.poller.setMaxRows(this.maxRows);
}
where that JdbcPollingChannelAdapter has this logic:
By default it is private int maxRows = 0;
return new PreparedStatementCreatorWithMaxRows(preparedStatementCreator,
JdbcPollingChannelAdapter.this.maxRows);
And that one:
public PreparedStatement createPreparedStatement(Connection con) throws SQLException {
PreparedStatement preparedStatement = this.delegate.createPreparedStatement(con);
preparedStatement.setMaxRows(this.maxRows); // We can't mutate provided JdbOperations for this option
return preparedStatement;
}
Then PreparedStatement:
/**
* Sets the limit for the maximum number of rows that any
* {#code ResultSet} object generated by this {#code Statement}
* object can contain to the given number.
* If the limit is exceeded, the excess
* rows are silently dropped.
*
* #param max the new max rows limit; zero means there is no limit
* #throws SQLException if a database access error occurs,
* this method is called on a closed {#code Statement}
* or the condition {#code max >= 0} is not satisfied
* #see #getMaxRows
*/
void setMaxRows(int max) throws SQLException;
zero means there is no limit
The logic in the JdbcOutboundGateway in the end is like this:
if (list.size() == 1 && (this.maxRows == null || this.maxRows == 1)) {
payload = list.get(0);
}
So, we return one record only if ResultSet has only one element.
I doubt we can do anything from Spring Integration perspective, unless you want to try with an Integer.MAX_VALUE for this property since your JDBC communication does not honor PreparedStatement.setMaxRows() contract.