: *pk*: The primary key for the entity. It is*optional*and only needed when : using delta-imports. It has no relation to the uniqueKey defined in schema.xml : but they both can be the same. : : When using in a nested entity is the PK the primary key column of the join : table or the key used for joining? For example
As i understand it, the "pk" is the field(s) in that entity that can be used to join that entity with other entities (either up or down) Note in particular the example on the wiki, and how the "item_category" entity has pk="ITEM_ID, CATEGORY_ID" ... "ITEM_ID" is used to join "up" to the "item" entity, and "CATEGORY_ID" is used to join "down" to the "category" entity... https://wiki.apache.org/solr/DataImportHandler#Delta-Import_Example (If that example isn't super clear, it may help to look at the table definitions in solr/example/example-DIH/hsqldb/ex.script) -Hoss
