[LUCENE-3105] String.intern() calls slow down IndexWriter.close() and IndexReader.open() for index with large number of unique field names

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 3.1
• Component/s: core/index
• Lucene Fields: New, Patch Available
• Assignee: Unassigned
• Reporter: Mark Kristensson
• Created: 16/May/11 22:16
• Updated: 28/Aug/22 12:46
• Resolved: 15/Jul/11 03:16

Description

We have one index with several hundred thousand unqiue field names (we're optimistic that Lucene 4.0 is flexible enough to allow us to change our index design...) and found that opening an index writer and closing an index reader results in horribly slow performance on that one index. I have isolated the problem down to the calls to String.intern() that are used to allow for quick string comparisons of field names throughout Lucene. These String.intern() calls are unnecessary and can be replaced with a hashmap lookup. In fact, StringHelper.java has its own hashmap implementation that it uses in conjunction with String.intern(). Rather than using a one-off hashmap, I've elected to use a ConcurrentHashMap in this patch.

Issue Links

• relates to: LUCENE-2548 Remove all interning of field names from flex API