Adding child documents to existing Solr 6.4 collection documents creates duplicate documents

Question

This question is similar to Solr doesn\'t overwrite - duplicated uniqueKey entries, but I am in a situation where I have a large body of existing documents that have already

Answer 1

I would strongly advise avoiding Solr parent/child relationships. We decided to use them in Solr 5.3.1 and it turns out that although much of the functionality is there, there are a number of nasty bugs present in Solr since 4.x that remain unfixed including

• SOLR-6096: Support Update and Delete on nested documents
• SOLR-5211: updating parent as childless makes old children orphans (UPDATE: fixed in 8.0)
• SOLR-6596: Atomic update and adding child doc not working together
• SOLR-5772: duplicate documents between solr "block join" documents and "normal" document
• SOLR-10030: SolrClient.getById() method in Solrj doesn't retrieve child documents

For those reasons, if at all possible, I strongly recommend AVOID using child documents. Even if those issues don't hit you now they will in the future at some point and it's clear, given that they have not been fixed in 3 to 4 major versions, that there is no real support in the product for child documents. Sorry to be the bearer of bad news but hopefully someone can learn from our experience.