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From Michael McCandless <luc...@mikemccandless.com>
Subject Re: Lucene 2.9 and deprecated IR.open() methods
Date Mon, 05 Oct 2009 12:11:28 GMT
I think AS is overkill for conveying configuration of IW/IR?

Suddenly, instead of:

  cfg.setRAMBufferSizeMB(128.0)

I'd have to do something like this?

  cfg.addAttribute(IndexWriterRAMBufferSizeAttribute.class).setRAMBufferSize(128.0)

It's too cumbersome, I think, for something that ought to be simple.
I'd prefer a dedicated config class with strongly typed setters
exposed.  Of all the "pure syntax" options so far I'd still prefer the
traditional "config object with setters".

Also, I don't think we should roll this out for all Lucene classes.  I
think most classes do just fine accepting args to their ctor.  EG
TermQuery simply takes Term to its ctor.

I do agree IW should not be in the business of brokering changes to
the settings of its sub-components (eg mergeFactor, maxMergeDocs).
You really should make such changes directly via your merge policy.

Finally, I'm not convinced we should lock down all settings after
classes are created.  (I'm not convinced we shouldn't, either).

A merge policy has no trouble changing its mergeFactor,
maxMergeDocs/Size.  IW has no trouble changing the its RAM buffer
size, maxFieldLength, or useCompoundFile.  Sure there are some things
that cannot (or would be very tricky to) change, eg deletion policy.
But then analyzer isn't changeable today, but could be.

But, then, I can also see it'd simplify our code to not have to deal
w/ such changes, reduce chance of subtle bugs, and it seems minor to
go and re-open your IndexWriter if you need to make a settings change?
(Hmm except in an NRT setting, because the reader pool would be reset;
really we need to get the reader pool separated from the IW instance).

Mike

On Mon, Oct 5, 2009 at 4:38 AM, Uwe Schindler <uwe@thetaphi.de> wrote:
>> > See my second mail. The recently introduced Attributes and
>> AttributeSource
>> > would solve this. Each component just defines its attribute interface
>> and
>> > impl class and you pass in an AttributeSource as configuration. Then you
>> can
>> > do:
>> >
>> > AttributeSource cfg = new AttributeSource();
>> >
>> > ComponentAttribute compCfg = cfg.addAttribute(ComponentAttribute.class);
>> > compCfg.setMergeScheduler(FooScheduler.class);
>> >
>> > MergeBarAttribute mergeCfg = cfg.addAttribute(MergeBarAttribute.class);
>> > mergeCfg.setWhateverProp(1234);
>> > ...
>> > IndexWriter iw = new IndexWriter(dir, cfg);
>> >
>> > (this is just brainstorming not yet thoroughly thought about).
>>
>> This approach suggests IW creates its components, and while doing so
>> provides them your AS instance.
>> I personally prefer creating all these components myself, configuring
>> them (at the moment of creation) and passing them to IW in one way or
>> another.
>> This requires way less code, you don't have to invent elaborate
>> schemes of passing through your custom per-component settings and
>> selecting which exact component types IW should use, you don't risk
>> construct/postConstruct/postpostConstruct-style things.
>
>
> Not really. That was just brainstorming. But you can pass also instances
> instead of class names through attributesource. AttributeSurce only provides
> type safety for the various configuration settings (which are interfaces).
> But you could also create an attribute that gets the pointer to the
> component. So "compCfg.setMergeScheduler(FooScheduler.class);" could also be
> compConfig.addComponent(new FooScheduler(...));
>
> The AttributeSource approach has one other good thing:
> If you want to use the default settings for one attribute, you do not have
> to add it to the AS (or you can forget it). With the properties approach,
> you have to hardcode the parameter defaults and validation everywhere. As
> the consumer of an AttributeSource gets the attribute also by an
> addAttribute-call (see current indexing code consuming TokenStreams), this
> call would add the missing attribute with its default settings defined by
> the implementation class. So in the above example, if you do not want to
> provide the "whateverProp", leave the whole MergeBarAttribute out. The
> consumer (IW) would just call addAttribute(MergeBarAttribute.class), because
> it needs the attribute to configure itself. AS would add this attribute with
> default settings.
>
> Uwe
>
>
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