# Ferret crash when using lazy\_doc after closing IndexReader

**URL:** <https://www.ruby-forum.com/t/ferret-crash-when-using-lazy-doc-after-closing-indexreader/153238>\
**Category:** Ferret\
**Created:** [November 13, 2008, 7:30pm UTC](https://www.ruby-forum.com/t/ferret-crash-when-using-lazy-doc-after-closing-indexreader/153238 "2008-11-13T19:30:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Eduardo\_Habkost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/e/90db22/32.png) [@Eduardo\_Habkost](https://www.ruby-forum.com/u/Eduardo_Habkost)\
**Post date:** [November 13, 2008, 7:30pm UTC](https://www.ruby-forum.com/t/ferret-crash-when-using-lazy-doc-after-closing-indexreader/153238/1 "2008-11-13T19:30:13Z")

</div>

Hi,

As the Ferret site is down for a while, I am reporting this bug here,  
so it gets documented somewhere and people with more experience with  
Ferret can comment.

I was hitting this crash easily on Sup, that uses Ferret for its  
index[1]. After some investigation I’ve found the cause of the crash,  
but I don’t know what would be the best behaviour for Ferret on this  
case.

The crash happens when the IndexReader object where a lazy\_doc was  
loaded  
from gets closed. After closing the IndexReader, trying to get a field  
from the lazy\_doc will trigger a read from a closed and freed  
InputStream,  
sometimes causing segfaults, sometimes causing spurious I/O errors.

I’ve initially seen the bug using Ferret 0.11.6, but I’ve tested this  
using Ferret from the git repository[2], and it happens there, also.

Below is a simple script that will trigger the crash:

========================================

# Example A

require “ferret”

p = “/tmp/ferret-test.#$$”  
puts “Using #{p} as storage”

i = Ferret::Index::Index.new(:path =\> p)  
i \<\< { :body =\> "Loren ipsum dolor "\*1000 }  
doc = i[0]

# this will cause the IndexReader to be closed by Ferret::Index::Index

i \<\< { :body =\> “another document” }

# puts doc[:body]

It happens because writing to the Ferret index will close the  
IndexReader.  
A simpler code that trigger the crash is:

========================================

# Example B

require “ferret”

p = “/tmp/ferret-test.#$$”  
puts “Using #{p} as storage”

puts “Generating a simple index”  
i = Ferret::Index::Index.new(:path =\> p)  
i \<\< { :body =\> "Loren ipsum dolor "\*1000 }  
i.close

puts “Closed it. Will reopen and use it”  
i = Ferret::Index::IndexReader.new(p)  
doc = i[0]  
i.close

# puts doc[:body]

I see two issues here:

The first one is the crash itself: what should happen to loaded  
lazy\_docs  
when an IndexReader is closed? Lucene documentation[3] says an exception  
may be thrown on these cases. The same behavior could be the proper fix  
for Ferret on Example B, that can be considered invalid usage of the  
IndexReader anyway.

The second issue is what should be the behaviour of Ferret::Index::Index  
after writing to the index with documents loaded (Example A). Should it  
really invalidate all lazy\_docs read from the index on every write? That  
is the current behavior because its IndexReader is always closed when  
writing to the index, but I wonder if it is really desired.

[1] [http://rubyforge.org/pipermail/sup-talk/2008-November/001782.html](http://rubyforge.org/pipermail/sup-talk/2008-November/001782.html)  
[2] [GitHub - dbalmain/ferret: Ferret: the extensible information retrieval library for ruby.](http://github.com/dbalmain/ferret)  
[3]  
[http://lucene.apache.org/java/2\_4\_0/api/core/org/apache/lucene/index/IndexReader.html#document(int,%20org.apache.lucene.document.FieldSelector)](http://lucene.apache.org/java/2_4_0/api/core/org/apache/lucene/index/IndexReader.html#document(int,%20org.apache.lucene.document.FieldSelector))