lucene-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Andrzej Bialecki (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2455) Some house cleaning in addIndexes*
Date Mon, 17 May 2010 13:45:42 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12868221#action_12868221
] 

Andrzej Bialecki  commented on LUCENE-2455:
-------------------------------------------

bq. So can't the PrunningReader run on the side, converting the postings to whatever they're
supposed to look like 

Erhm ... Currently the only way in the user API to write out existing postings (no matter
how created) is to use IndexWriter.addIndexes(IndexReader). We can read postings just fine,
using various *Enum classes that we can obtain from IndexReader, but there are no comparable
high-level output methods  - Codecs and other flex classes are IMHO too low-level.

Also, with large indexes the amount of IO/CPU for writing out a Directory and reopening it
is non-trivial - it's much more efficient to do this via streaming from the original, already
open index.

Also, if we remove this method, then FilterIndexReader may as well go too, because it loses
its utility.

> Some house cleaning in addIndexes*
> ----------------------------------
>
>                 Key: LUCENE-2455
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2455
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>            Reporter: Shai Erera
>            Assignee: Shai Erera
>            Priority: Trivial
>             Fix For: 3.1, 4.0
>
>         Attachments: LUCENE-2455_3x.patch
>
>
> Today, the use of addIndexes and addIndexesNoOptimize is confusing - 
> especially on when to invoke each. Also, addIndexes calls optimize() in 
> the beginning, but only on the target index. It also includes the 
> following jdoc statement, which from how I understand the code, is 
> wrong: _After this completes, the index is optimized._ -- optimize() is 
> called in the beginning and not in the end. 
> On the other hand, addIndexesNoOptimize does not call optimize(), and 
> relies on the MergeScheduler and MergePolicy to handle the merges. 
> After a short discussion about that on the list (Thanks Mike for the 
> clarifications!) I understand that there are really two core differences 
> between the two: 
> * addIndexes supports IndexReader extensions
> * addIndexesNoOptimize performs better
> This issue proposes the following:
> # Clear up the documentation of each, spelling out the pros/cons of 
>   calling them clearly in the javadocs.
> # Rename addIndexesNoOptimize to addIndexes
> # Remove optimize() call from addIndexes(IndexReader...)
> # Document that clearly in both, w/ a recommendation to call optimize() 
>   before on any of the Directories/Indexes if it's a concern. 
> That way, we maintain all the flexibility in the API - 
> addIndexes(IndexReader...) allows for using IR extensions, 
> addIndexes(Directory...) is considered more efficient, by allowing the 
> merges to happen concurrently (depending on MS) and also factors in the 
> MP. So unless you have an IR extension, addDirectories is really the one 
> you should be using. And you have the freedom to call optimize() before 
> each if you care about it, or don't if you don't care. Either way, 
> incurring the cost of optimize() is entirely in the user's hands. 
> BTW, addIndexes(IndexReader...) does not use neither the MergeScheduler 
> nor MergePolicy, but rather call SegmentMerger directly. This might be 
> another place for improvement. I'll look into it, and if it's not too 
> complicated, I may cover it by this issue as well. If you have any hints 
> that can give me a good head start on that, please don't be shy :). 

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org


Mime
View raw message