[LUCENE-1789] getDocValues should provide a MultiReader DocValues abstraction

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.9
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Chris M. Hostetter
• Created: 07/Aug/09 00:31
• Updated: 28/Aug/22 12:05
• Resolved: 13/Aug/09 19:40

Description

When scoring a ValueSourceQuery, the scoring code calls ValueSource.getValues(reader) on each leaf level subreader – so DocValue instances are backed by the individual FieldCache entries of the subreaders – but if Client code were to inadvertently called getValues() on a MultiReader (or DirectoryReader) they would wind up using the "outer" FieldCache.

Since getValues(IndexReader) returns DocValues, we have an advantage here that we don't have with FieldCache API (which is required to provide direct array access). getValues(IndexReader) could be implimented so that IF some a caller inadvertently passes in a reader with non-null subReaders, getValues could generate a DocValues instance for each of the subReaders, and then wrap them in a composite "MultiDocValues".