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https://issues.apache.org/jira/browse/LUCENE-4132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13292793#comment-13292793
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Shai Erera commented on LUCENE-4132:
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bq. Today someone can take the config off of there and set it on another writer
(it will be privately cloned)
True, but I'm not aware of such use, and still someone can cache the IWC
himself and pass it to multiple writers?
If getConfig() returns an IWC which has setters(), that'll confuse the user for
sure, because those settings won't take effect.
I prefer that getConfig return the new LiveConfig type, with few setters and
all getters (i.e. all getXYZ from IWC), and let whoever want to pass the same
IWC instance to other writers handle it himself.
Alternatively, we can add another ctor which takes a LiveConfig object, that is
returned from getConfig(), but I prefer to avoid that until someone actually
tells us that he shares the same IWC with other writers, and he cannot cache it
himself?
> IndexWriterConfig live settings
> -------------------------------
>
> Key: LUCENE-4132
> URL: https://issues.apache.org/jira/browse/LUCENE-4132
> Project: Lucene - Java
> Issue Type: Improvement
> Reporter: Shai Erera
> Priority: Minor
> Fix For: 4.0, 5.0
>
>
> A while ago there was a discussion about making some IW settings "live" and I
> remember that RAM buffer size was one of them. Judging from IW code, I see
> that RAM buffer can be changed "live" as IW never caches it.
> However, I don't remember which other settings were decided to be "live" and
> I don't see any documentation in IW nor IWC for that. IW.getConfig mentions:
> {code}
> * <b>NOTE:</b> some settings may be changed on the
> * returned {@link IndexWriterConfig}, and will take
> * effect in the current IndexWriter instance. See the
> * javadocs for the specific setters in {@link
> * IndexWriterConfig} for details.
> {code}
> But there's no text on e.g. IWC.setRAMBuffer mentioning that.
> I think that it'd be good if we make it easier for users to tell which of the
> settings are "live" ones. There are few possible ways to do it:
> * Introduce a custom @live.setting tag on the relevant IWC.set methods, and
> add special text for them in build.xml
> ** Or, drop the tag and just document it clearly.
> * Separate IWC to two interfaces, LiveConfig and OneTimeConfig (name
> proposals are welcome !), have IWC impl both, and introduce another
> IW.getLiveConfig which will return that interface, thereby clearly letting
> the user know which of the settings are "live".
> It'd be good if IWC itself could only expose setXYZ methods for the "live"
> settings though. So perhaps, off the top of my head, we can do something like
> this:
> * Introduce a Config object, which is essentially what IWC is today, and pass
> it to IW.
> * IW will create a different object, IWC from that Config and IW.getConfig
> will return IWC.
> * IWC itself will only have setXYZ methods for the "live" settings.
> It adds another object, but user code doesn't change - it still creates a
> Config object when initializing IW, and need to handle a different type if it
> ever calls IW.getConfig.
> Maybe that's not such a bad idea?
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