[SOLR-15291] Test + ref-guide note about "safe" way to de-duplicate documents in SolrCloud

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 9.0, 8.9
• Assignee: Chris M. Hostetter
• Reporter: Chris M. Hostetter
• Created: 25/Mar/21 18:23
• Updated: 23/Jun/21 13:42
• Resolved: 26/Mar/21 17:14

Description

• The only "safe" way to use SignatureUpdateProcessorFactory for de-duplication in SolrCloud is to define the signatureField to be the same as the unique key field – ie: let SignatureUpdateProcessorFactory generate the 'id' for each document
  • We should add a note about this to the ref-guide ASAP for inclusion in the next release
• There are currently no "cloud" based tests of SignatureUpdateProcessorFactory showing that even this usage works
  • We should add a basic test of this usage ASAP to future-proof against it breaking