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From lucene-...@jakarta.apache.org
Subject [Jakarta Lucene Wiki] Updated: LuceneFAQ
Date Sun, 02 Jan 2005 13:36:37 GMT
   Date: 2005-01-02T05:36:37
   Editor: DanielNaber
   Wiki: Jakarta Lucene Wiki
   Page: LuceneFAQ
   URL: http://wiki.apache.org/jakarta-lucene/LuceneFAQ

   no comment

Change Log:

------------------------------------------------------------------------------
@@ -55,7 +55,19 @@
 
 No, check out the [http://java-source.net/open-source/crawlers list of Open Source Crawlers
in Java].
 
- 
+
+==== Why am I getting an IOException that says "Too many open files"? ====
+
+The number of files that can be opened simultaneously is a system-wide limitation of your
operating system. Lucene might cause this problem as it can open quite some files depending
on how you use it, but the problem might also be somewhere else.
+
+ * Always make sure that you ''explicitly'' close all file handles you open, especially in
case of errors. Use a try/catch/finally block to open the files, i.e. open them in the try
block, close them in the finally block. Remember that Java doesn't have destructors, so don't
close file handles in a finalize method -- this method is not guaranteed to be executed.
+ * Use the compound file format (it's activated by default starting with Lucene 1.4) by calling
 [http://jakarta.apache.org/lucene/docs/api/org/apache/lucene/index/IndexWriter.html#setUseCompoundFile(boolean)
IndexWriter's setUseCompoundFile(true)]
+ * Don't set [http://jakarta.apache.org/lucene/docs/api/org/apache/lucene/index/IndexWriter.html#mergeFactor
IndexWriter's mergeFactor] to large values. Large values speed up indexing but increase the
number of files that need to be opened simultaneously.
+ * If the exception occurs during searching, optimize your index calling  [http://jakarta.apache.org/lucene/docs/api/org/apache/lucene/index/IndexWriter.html#optimize()
IndexWriter's optimize()] method after indexing is finished.
+ * Try to increase the number of files that can be opened simultaneously. On Linux using
bash this can be done by calling `ulimit -n <number>`.
+
+
+
 
 === Searching ===
 
@@ -95,7 +107,7 @@
 
 ==== How do I restrict searches to only return results from a limited subset of documents
in the index (e.g. for privacy reasons)? What is the best way to approach this? ====
 
-The QueryFilter http://jakarta.apache.org/lucene/docs/api/org/apache/lucene/search/QueryFilter.html
class is designed precisely for such cases.
+The [http://jakarta.apache.org/lucene/docs/api/org/apache/lucene/search/QueryFilter.html
QueryFilter class] is designed precisely for such cases.
 
 Another way of doing it is the following:
 
@@ -129,7 +141,7 @@
 
 ==== Does MultiSearcher do anything particularly efficient to search multiple indices or
does it simply search one after the other? ====
 
-`MultiSearcher` searches indices sequentially. Use ParallelMultiSearcher as a searcher that
performs multiple searches in parallel.
+`MultiSearcher` searches indices sequentially. Use [http://jakarta.apache.org/lucene/docs/api/org/apache/lucene/search/ParallelMultiSearcher.html
ParallelMultiSearcher] as a searcher that performs multiple searches in parallel.
 
 
 ==== Is there a way to use a proximity operator (like near or within) with Lucene? ====

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