Thanks for the tip Josh.

I'm probs missing something basic but I didn't have any success with metadata passed into the query web part having any impact.

I pass: (note I tried making a change to the column title just to check the metadata was having an impact)

<tables xmlns="http://labkey.org/data/xml"><table tableName="Dummy" tableDbType="NOT_IN_DB"><columns><column columnName="lsid"><isKeyField>false</isKeyField></column><column columnName="ABC"><columnTitle>ABD</columnTitle><isKeyField>true</isKeyField></column></columns></table></tables>

No change however.

As an additional test, I applied that xml against the actual dataset through the schema browser - the metadata is then reflected in the Query Schema Browser, however even then, the lsid is returned from the querywebpart :(.

Cheers,
Trent

nb: I realise this example is different again to my original post, but I did also try assigning the ParticipantSequenceNum as the primary key - and just wanted to provide a sample of applying xml. And here is the full code:

<script type="text/javascript">
    var dummyWebPart =
        new LABKEY.QueryWebPart({
                renderTo: 'container',
                title: 'Dummy',
                schemaName: 'study',
                queryName: 'Dummy',
                showRecordSelectors: true,
                buttonBar: {
                    includeStandardButtons: true,
                    items:[
                      {text: 'Show Vials', onClick: "console.log(dummyWebPart.getDataRegion().getChecked())", requiresSelection: true},
                    ]
                },
                metadata: {
                    type: 'xml',
                    value: '<tables xmlns="http://labkey.org/data/xml"><table tableName="Dummy" tableDbType="NOT_IN_DB"><columns><column columnName="lsid"><isKeyField>false</isKeyField></column><column columnName="ABC"><columnTitle>ABD</columnTitle><isKeyField>true</isKeyField></column></columns></table></tables>'
                }
        });
</script>
<div id="container"></div>