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From Rajesh parab <>
Subject ParalleReader and synchronization between indexes
Date Tue, 29 Apr 2008 17:05:31 GMT

This is from javadoc of ParallelReader:


An IndexReader which reads multiple, parallel indexes.
Each index added must have the same number of
documents, but typically each contains different
fields. Each document contains the union of the fields
of all documents with the same document number. When
searching, matches for a query term are from the first
index added that has the field. 

This is useful, e.g., with collections that have large
fields which change rarely and small fields that
change more frequently. The smaller fields may be
re-indexed in a new index and both indexes may be
searched together.


I have a similar use case as mentioned above and hence
would like to use ParallelReader to search across
multiple indexes.

I have an object that has 50 fields. Out of these 50
fields, 45 are relatively static and other 5 are
modified very often. So, I am planning to partition
this objects data into 2 indexes such that 45 static
fields will be part of one index and remaining 5
dynamic fields will constitute second index. While
generating the index for the first time, I can make
sure that the document order for documents inside both
these indexes is same and hence ParallelReader will
work properly with it.

The question is -
What if the data inside second (smaller) index
changes? In order to update index document, I will
have to delete it and re-insert it again as Lucene
does not support document update. This action (of
delete and re-insert) will change internal document id
for updated document inside second index and in order
to sync it with first index, I will have to also
modify first (relatively big and static) index. If we
will have to update both the indexes, how it is
different from having a single index with all the
fields? What is the use case in which ParallelReader
will get used? As per documentation, I was thinking
that it will apply for my use case, but synchronizing
the indexes seems to be a problem.

Please help.


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