[LUCENE-9972] Performance regression in NRTCachingDirectory

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 8.8.2
• Component/s: core/store
• Labels: performance
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Markus Gietzen
• Created: 25/May/21 06:51
• Updated: 28/Aug/22 16:22

Description

This issue has been discussed here:

http://mail-archives.apache.org/mod_mbox/lucene-java-user/202105.mbox/[e-mail]%3e

 

Summary: To get the same speed as in 8.3 I have to overwrite NRTCachingDirectory#doCacheWrite

in 8.8 with the implementation from 8.3. Otherwise it's magnitudes slower.

 

It seems that the solution for https://issues.apache.org/jira/browse/LUCENE-9115 increases the number of calls to native-OpenFile (due to falling down to MMAP-Directory) by a very  large amount.

I understand the reasoning behind LUCENE-9115 but in fact it destroys the performance of our product. For now sub-classing NRTCachingDirectory with the old implementation of doCacheWrite() solves the issue but it would be great to have an "offical" solution of course.