See https://issues.apache.org/jira/browse/LUCENE-8551

The main thing missing is that the stored fields data doesn't actually store what IDs are being used (!).  If that were in place, I could imagine a CLI tool to purge the IDs.

~ David Smiley
Apache Lucene/Solr Search Developer


On Mon, Mar 9, 2020 at 2:53 PM Michael Kleen <mkleen@gmail.com> wrote:
Hello, 

i am interested in the implementation of the field removal from an index. I am a Lucene user and I have a basic understanding of the internals. I have a few first questions and I hope this is the right place to ask them.

Is already someone working on this topic ?

Are there some real blockers for this feature ?

From my basic understanding, field removal should work conceptually in the following way: The FieldInfo which is supposed to be removed would need to be first stored until the segment merge is happening. Once the segment merge is happening the field has to excluded from the new segment. Is this correct, or do I miss something here ? 

Thank you for your time,

Michael