push.scheduler.killed-percentage-for-reindex (collection.cfg setting)
The percentage of documents which must already be killed in a set of merging generations for the new generation to re-index the merged WARC file (rather than merging the indexes).
A lower value will result in more frequent re-indexing, producing improved ranking at the cost of more computation time per merge. A higher value reduces merge times at the cost of lower search quality, increased disk space usage and slower query processing times.
By default, a Push collection will re-index when 50% of the documents have been killed.
To set a Push collection to re-index on every merge: