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Query Pooling

Prepared expressions let the programmer decide when a query should be prepared and when a prepared query is no longer needed. In programs that use hundreds or thousands of queries, it is generally better to let DataDirect XQuery® keep track of which queries are actually being used, preparing them the first time they are executed, and discarding the least frequently used prepared queries if there are too many queries. This is called query pooling.

In DataDirect XQuery®, you enable query pooling by specifying the number of prepared queries to hold in the pool. If you configure your connection by setting properties in the Java API, you can set the MaxPooledQueries property to do this; for instance, the following code sets the size of the query pool to 20:

Example 4. Enabling Query Pooling with the Java API

    XQDataSource dataSource = new DDXQDataSource();    
    dataSource.setJdbcUrl("jdbc:xquery:sqlserver://server1:1433;databaseName=stocks");
    dataSource.setMaxPooledQueries(20);                
    XQConnection connection = dataSource.getConnection();
        

If you configure your connection using a Source Configuration File, you can set the size of the query pool using the maxPooledQueries element:

Example 5. Enabling Query Pooling in a Source Configuration File

                
<?xml version="1.0" encoding="UTF-8"?>
<XQJConnection xmlns="http://www.datadirect.com/xquery">

	<maxPooledQueries>20</maxPooledQueries>    
	<JDBCConnection name="stocks">
        <url>jdbc:xquery:sqlserver://localhost:1433</url>
        <sqlxmlMapping>
            <forest>true</forest>
            <identifierEscaping>none</identifierEscaping>
        </sqlxmlMapping>
    </JDBCConnection>
</XQJConnection>