[LUCENE-1579] Cloned SegmentReaders fail to share FieldCache entries

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.9
• Fix Version/s: 2.9
• Component/s: core/index
• Lucene Fields: New
• Assignee: Michael McCandless
• Reporter: Michael McCandless
• Created: 28/Mar/09 16:04
• Updated: 28/Aug/22 11:58
• Resolved: 31/Mar/09 15:41

Description

I just hit this on LUCENE-1516, which returns a cloned readOnly
readers from IndexWriter.

The problem is, when cloning, we create a new [thin] cloned
SegmentReader for each segment. FieldCache keys directly off this
object, so if you clone the reader and do a search that requires the
FieldCache (eg, sorting) then that first search is always very slow
because every single segment is reloading the FieldCache.

This is of course a complete showstopper for LUCENE-1516.

With LUCENE-831 we'll switch to a new FieldCache API; we should ensure
this bug is not present there. We should also fix the bug in the
current FieldCache API since for 2.9, users may hit this.