Solr DIH delta-import with compound primary keys?

Question

My Solr data source is a SQL database where the primary key is compound (i.e. it's two fields).

This is fine for my main DIH query, I just concatenate the fields and that becomes my Solr primary key. However it's unclear from the documentation how I'd write a delta-import query to support this.

The documentation suggests I need two queries - one to find the primary key of the changed rows, and another to then actually retrieve the individual documents corresponding to each of those keys. There's no example showing this for compound keys though.

Ideally I don't want those two separate queries at all, it would put less load on the database if those two queries were simply combined such that the only difference between query and deltaQuery is the WHERE clause that filters based on last_changed.

So, if my main query is:

SELECT key1 || key2 as pk FROM table

What would the relevant deltaQuery (and/or deltaImportQuery) look like?

I tried just adding the WHERE clause but after the query ran I got a warning about the missing deltaImportQuery and then a null-pointer exception.

Answer 1

query="SELECT key1 || key2 as id, ...other fields FROM table"

deltaImportQuery="SELECT key1 || key2 as id, ... other fields
                  FROM table
                  where key1 = '${dataimporter.delta.key1}'
                  and key2 = '${dataimporter.delta.key2}'"

deltaQuery="SELECT key1 || key2 as id, key1, key2
            FROM table
            WHERE lastUpdated > '${dataimporter.last_index_time}'"

Assuming key1 and key2 are text. The single quotes around ${dataimporter.delta.key2} wouldn't be needed if key2 is numeric for example.