locking problems

[Aad Nales <aa...@rotterdam-cs.com>]

Based on discussions in this group I figure that I should 'cache'
IndexSearchers and IndexReaders, which i did. I have build an
IndexSearcherPool and an IndexReaderPool. Both seem to work fine
(although I am still testing). However, whenever I use these I can not
create an IndexWriter. The thread fails and generates a timeout on
org.apache.lucene.store.Lock.obtain (1.3.1) in line 97.

Can somebody help me to figure out with what actions these locks are
obtained? I have been reading all faq's on the subject but failed to
understand the following:

1. can I have one or multiple searchers open when I open a writer?
2. can I have one or multiple readers open when I open a writer?

And if not. I am writing an application that does regular updates on the
index what kind of strategy could you advise? Should  I use
ResourcePooling at all?

TIA,
Aad Nales


--
Aad Nales
aad.nales@rotterdam-cs.com, +31-(0)6 54 207 340 



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Re: locking problems

[Doug Cutting <cu...@apache.org>]

Aad Nales wrote:
> 1. can I have one or multiple searchers open when I open a writer?
> 2. can I have one or multiple readers open when I open a writer?

Yes, with one caveat: if you've called the IndexReader methods delete(), 
undelete() or setNorm() then you may not open an IndexWriter until 
you've closed that IndexReader instance.

In general, only a single object may modify an index at once, but many 
may access it simultaneously in a read-only manner, including while it 
is modified.  Indexes are modified by either an IndexWriter or by the 
IndexReader methods delete(), undelete() and setNorm().

Typically an application which modifies and searches simultaneously 
should keep the following open:

   1. A single IndexReader instance used for all searches, perhaps 
opened via an IndexSearcher.  Periodically, as the index changes, this 
is discarded, and replaced with a new instance.

   2. Either:
      a. An IndexReader to delete documents.
      b. An IndexWriter to add documents; or

So an updating thread might open (2a), delete old documents, close it, 
then open (2b) add new documents, perhaps optimize, then close.  At this 
point, when the index has been updated (1) can be discarded and replaced 
with a new instance.  Typically the old instance of (1) is not 
explicitly closed, rather the garbage collector closes it when the last 
thread searching it completes.

Doug

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