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From "Michael Busch (JIRA)" <>
Subject [jira] Commented: (LUCENE-648) Allow changing of ZIP compression level for compressed fields
Date Fri, 11 Aug 2006 05:18:15 GMT
    [ ] 
Michael Busch commented on LUCENE-648:

I think the compression level is only one part of the performance problem. Another drawback
of the current implementation is how compressed fields are being merged: the FieldsReader
uncompresses the fields, the SegmentMerger concatenates them and the FieldsWriter compresses
the data again. The uncompress/compress steps are completely unnecessary and result in a large
overhead. Before a document is written to the disk, the data of its fields is even being compressed
twice. Firstly, when the DocumentWriter writes the single-document segment to the RAMDirectory,
secondly, when the SegmentMerger merges the segments inside the RAMDirectory to write the
merged segment to the disk.

Please checkout Jira Issue 629 (, where I
recently posted a patch that fixes this problem and increases the indexing speed significantly.
I also included some performance test results which quantify the improvement. Mike, it would
be great if you could also try out the patched version for your tests with the compression

> Allow changing of ZIP compression level for compressed fields
> -------------------------------------------------------------
>                 Key: LUCENE-648
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.0.0, 1.9, 2.0.1, 2.1
>            Reporter: Michael McCandless
>            Priority: Minor
> In response to this thread:
> I think we should allow changing the compression level used in the call to
in  Right now it's hardwired to "best":
>       compressor.setLevel(Deflater.BEST_COMPRESSION);
> Unfortunately, this can apparently cause the zip library to take a very long time (10
minutes for 4.5 MB in the above thread) and so people may want to change this setting.
> One approach would be to read the default from a Java system property, but, it seems
recently (pre 2.0 I think) there was an effort to not rely on Java System properties (many
were removed).
> A second approach would be to add static methods (and static class attr) to globally
set the compression level?
> A third method would be in document.Field class, eg a setCompressLevel/getCompressLevel?
 But then every time a document is created with this field you'd have to call setCompressLevel
since Lucene doesn't have a global Field schema (like Solr).
> Any other ideas / prefererences for either of these methods?

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