Web-API asset requests returning empty result set

Migrateduser

Hi - we're using the Web API to sync assets with our website.   We have a large sync backlog, and we're finding that the call to "Search_GetAssetIDsOnly", with a criteria of "Accession-Id" "OpExists" is returning an empty set if we request all results by specifying MaxHits to be "0".   This request also returns an empty set for MaxHits set to larger numbers, such as "20000".   If we set the MaxHits to be something small, such as "10", then we get results, so we know that the request is processing and returning results, and that there are in fact assets that meet this criteria.   

Here is the SOAP request we're using:

<Envelope xmlns="http://www.w3.org/2003/05/soap-envelope">
    <Body>
        <Search_GetAssetIDsOnly xmlns="http://www.mediabin.com">
            <!-- Optional -->
            <criteria>
                <mContainerID>{1D234D53-DD48-43FD-88B1-BD648BAF27C9}</mContainerID>
                <mAssetID></mAssetID>
                <mRecursive>true</mRecursive>
                <mSearchConstraints>
               <MBSearchConstraint>
                  <mMetadata>
                     <mID>{F7DBA04F-1C53-4D7D-A82F-4E6E59D86608}</mID>
                     <mName>Accession-ID</mName>
                  </mMetadata>
                  <mSearchOperator>OpExists</mSearchOperator>
                  <mBooleanOperator>NotSet</mBooleanOperator>
            </MBSearchConstraint>
            </mSearchConstraints>
            <mMaxHits>0</mMaxHits>
            </criteria>
        </Search_GetAssetIDsOnly>
    </Body>
</Envelope>

We believe this behavior is being caused by a timeout at the App server level, which is being caught and handled silently at the web service.   Regardless of our conjectures, we need to understand how to get our result set successfully.