Very slow queries

Question

I have a query that I precompile and invoke after setting a variable. I do this to precompile the queries in stored modules as precompiling the queries would seem like a good performance enhancement.
When I invoke the query, it returns in 122168.68 (ms)! Obviously this is not ideal so in an attempt to diagnose the problem, I run the same query (same code) but I hard code the value instead of using a variable. Much to my pleasure, the query returned in 17.039 (ms). Now this is great! The only problem is that we can’t go into production with a hard coded variable. Are there any ideas how I can work around this (or better, if there is a patch)?
The code is as follows (the element names have been changed to protect the innocent):
import java.io.File;
import com.sleepycat.db.Environment;
import com.sleepycat.db.EnvironmentConfig;
import com.sleepycat.dbxml.XmlContainer;
import com.sleepycat.dbxml.XmlManager;
import com.sleepycat.dbxml.XmlManagerConfig;
import com.sleepycat.dbxml.XmlQueryContext;
import com.sleepycat.dbxml.XmlQueryExpression;
import com.sleepycat.dbxml.XmlResults;
import com.sleepycat.dbxml.XmlValue;
class BDBTest
    public BDBTest()
        XmlContainer container;
        Environment dbEnv;
        XmlManager dbManager;
        XmlQueryContext queryContext;
        EnvironmentConfig envConf;
        XmlManagerConfig managerConfig;
        String xquery;
        XmlQueryExpression  xmlQueryExpression;
        container = null;
        dbEnv = null;
        dbManager = null;
        try
            envConf = new EnvironmentConfig();
            envConf.setAllowCreate(true);
            envConf.setInitializeCache(true);
            envConf.setInitializeLocking(true);
            envConf.setInitializeLogging(true);
            envConf.setTransactional(true);
            dbEnv = new Environment(new File("/opt/db"), envConf);
            managerConfig = new XmlManagerConfig();
            managerConfig.setAdoptEnvironment(true);
            managerConfig.setAllowAutoOpen(true);
            dbManager = new XmlManager(dbEnv, managerConfig);
            dbManager.setDefaultContainerType(XmlContainer.NodeContainer);
            container = dbManager.openContainer("db/test");
            queryContext = dbManager.createQueryContext();
            queryContext.setEvaluationType(XmlQueryContext.Eager);
            queryContext.setVariableValue("contentKey", new XmlValue("AlexUserhttp://mydomain.org/ns/1.0/some/test/value/HERE"));
            // This query is very slow.
            xquery = "declare namespace tf = \"http://mydomain.org/ns/0.1/test/format\"; " +
                "count (collection('db/test')/Record[ContentKey=$contentKey]/tf:TestDocument)";
            // This query is very fast.
            // xquery = "declare namespace tf = \"http://mydomain.org/ns/0.1/test/format\"; " +
               // "count (collection('db/test')/Record[ContentKey=\"AlexUserhttp://mydomain.org/ns/1.0/some/test/value/HERE\"]/tf:TestDocument)";
            xmlQueryExpression = dbManager.prepare(xquery, queryContext);
            String qPlan = xmlQueryExpression.getQueryPlan();
            System.out.println("--------------------------------------------------");
            System.out.println(qPlan);
            System.out.println("--------------------------------------------------");
            long ns0 = System.nanoTime();
            XmlResults results = xmlQueryExpression.execute(queryContext);
            long ns1 = System.nanoTime() - ns0;
            double ms1 = (double) ns1 / 1000000;
            String message = "Found ";
            message += results.size() + " documents for query: '";
            message += xquery + " Time to execute: " + ms1 + " (ms)\n";
            System.out.println(message);
            System.out.println(results.next().asNumber());
        catch (Exception e)
            e.printStackTrace(System.err);
    public static void main(String args[]) throws Throwable
        new BDBTest();
}The query plans are as follows:
SLOW:
<XQuery>
  <Function name="{http://www.w3.org/2005/xpath-functions}:count">
    <DocumentOrder>
      <DbXmlNav>
        <LookupIndex container="db/test">
          <ValueQP index="edge-element-equality-string" operation="eq" parent="Record" child="ContentKey">
            <Variable name="contentKey"/>
          </ValueQP>
        </LookupIndex>
        <Join type="parent-of-child" return="argument">
          <DbXmlNav>
            <QueryPlanFunction result="collection" container="db/test">
              <OQPlan>P(edge-element-equality-string,prefix,Record.ContentKey)</OQPlan>
            </QueryPlanFunction>
            <DbXmlStep axis="child" name="Record" nodeType="element"/>
          </DbXmlNav>
        </Join>
        <DbXmlStep axis="child" prefix="tf" uri="http://mydomain.org/ns/0.1/test/format" name="TestDocument" nodeType="element"/>
      </DbXmlNav>
    </DocumentOrder>
  </Function>
</XQuery>
Found 1 documents for query: 'declare namespace tf = "http://mydomain.org/ns/0.1/test/format"; count (collection('db/test')/Record[ContentKey=$contentKey]/tf:TestDocument) Time to execute: 122168.68 (msFAST:
<XQuery>
  <Function name="{http://www.w3.org/2005/xpath-functions}:count">
    <DocumentOrder>
      <DbXmlNav>
        <LookupIndex container="db/test">
          <ValueQP index="edge-element-equality-string" operation="eq" parent="Record" child="ContentKey" value="AlexUserhttp://mydomain.org/ns/1.0/some/test/value/HERE"/>
        </LookupIndex>
        <Join type="parent-of-child" return="argument">
          <DbXmlNav>
            <QueryPlanFunction result="collection" container="db/test">
              <OQPlan>V(edge-element-equality-string,Record.ContentKey,=,'AlexUserhttp:// ://mydomain.org/ns/1.0/some/test/value/HERE')</OQPlan>
            </QueryPlanFunction>
            <DbXmlStep axis="child" name="Record" nodeType="element"/>
          </DbXmlNav>
        </Join>
        <DbXmlStep axis="child" prefix="tf" uri="http://mydomain.org/ns/0.1/test/format" name="TestDocument" nodeType="element"/>
      </DbXmlNav>
    </DocumentOrder>
  </Function>
</XQuery>
Found 1 documents for query: 'declare namespace tf = "http://mydomain.org/ns/0.1/test/format"; count (collection('db/test')/Record[ContentKey="AlexUserhttp://mydomain.org/ns/1.0/some/test/value/HERE"]/tf:TestDocument) Time to execute: 17.039 (ms)We’re using Java with BDB 2.3.10 on CentOs 64 bit (but see this in other environments as well). I’m happy to give any more info.
Thank you for your help,
Alex

Answer 1

Hi Alex,
I've just answered this question here:
Re: XQuery Performance in BerkeleyDB
John