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solrdataimporthandler

Solr: deltaQuery / parentDeltaQuery / deltaImportQuery

Solr's documentation for DataImportHandler gives this table for the entity query attributes.

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That's not extremely descriptive. Can someone express here the difference and interaction between these query attributes? I have seen some code use deltaQuery and parentDeltaQuery to support nested entities, and I have seen others use deltaQuery and deltaImportQuery.

What is the purpose of choosing one of those over the other?

Solution

  • I see it now in the Solr Wiki: 

    * The query gives the data needed to populate fields of the Solr document in full-import
* The deltaImportQuery gives the data needed to populate fields when running a delta-import
* The deltaQuery gives the primary keys of the current entity which have changes since the last index time
* The parentDeltaQuery uses the changed rows of the current table (fetched with deltaQuery) to give the changed rows in the parent table. This is necessary because whenever a row in the child table changes, we need to re-generate the document which has that field.

    I missed this explanation on the first pass, and expected that information to show up in the table I posted. Strangely enough, Solr In Action spent less than 1 page of 600 explaining how to use DataImportHandler to read a database.