On 8/8/2016 3:10 AM, Callum Lamb wrote: > How true is this claim? Is optimizing still a good idea for the > general case?
For the general case, optimizing is not recommended. If there are a very large number of deleted documents, which does describe your situation, then there is definitely a benefit. In cases where there are a lot of deleted documents, scoring can be affected by the presence of the deleted documents, and the drop in index size after an optimize can result in a large performance boost. For the general case where there are not many deletes, there *is* a performance benefit to optimizing down to a single segment, but it is nowhere near as dramatic as it was in the 1.x/3.x days. The problem with optimizes in the general case is this: The performance hit that the optimize operation itself causes may not be worth the small performance improvement. If you have a time where your index is quiet enough that the optimize itself won't be disruptive, then you should certainly take advantage of that time and do the optimize, even if there aren't many deletes. There is another benefit to optimizes that doesn't get mentioned often: It can make subsequent normal merging operations during indexing faster, because there will not be as many large segments. Thanks, Shawn
