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From Doug Cutting <>
Subject RE: Indexing and Searching happening together
Date Fri, 01 Feb 2002 17:17:57 GMT
> From: Kelvin Tan []
> True (and it's great) that once an IndexReader is open, no 
> actions on the IndexWriter affect it. 
> However, if an IndexReader is opened _after_ indexing begins, 
> I suppose it'll throw an exception? Doesn't it mean that when 
> indexing is taking place, the search engine is effectively down...

No, an index is always searchable.  It should be possible to open an
IndexReader at any time, and a coherent version of the index will be
available for search.

> I suppose then, that if I still want to have the search 
> engine up whilst indexing (where indexing takes a non-trivial 
> amount of time), I'll have to index to a temporary location, 
> then copy the index files over?

No, that is not required.

> Alternatively, I guess it's 
> possible to open an IndexReader _before_ commencement of 
> indexing and provide this instance of IndexReader to clients 
> who need to search?

This can be a useful technique if you are performing a number of coordinated
deletions and insertions to an index, and wish them all to appear at once.


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