A merge writes out a fresh copy of all the data it's merging and then cleans up the old segments that are no longer needed. If you are force-merging to a single segment then that means it must write out a fresh copy of the entire shard. Only once it's finished making a new (huge) segment can it clean up the old segments.
Thank you. How do I track the forcemerge progress? How can I make it faster? Does the increasing of " indices . memory . index_buffer_size" help the speed?
There isn't much you can do to tune the speed of a merge. It's quite an expensive and complicated operation and on a large shard it can take a long time to complete.
Apache, Apache Lucene, Apache Hadoop, Hadoop, HDFS and the yellow elephant
logo are trademarks of the
Apache Software Foundation
in the United States and/or other countries.