Nested child documents disappear when some unrelated fields of a parent document are atomically updated, if the schema contains a catch-all dynamic field to ignore unknown fields like:
DistributedUpdateProcessor#getUpdatedDocument tries to reconstruct the original document, but it does not receive nested documents from RealTimeComponent#getInputDocument. Nested documents are correctly found in the index but get lost when RealTimeGetComponent#toSolrInputDocument creates a SolrInputDocument for it. The problematic code is:
The code finds the "ignored" SchemaField as matching field for the nested document name (loaded from nest_path). Because of that they're not added to the SolrInputDocument.