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https://issues.apache.org/jira/browse/LUCENE-4132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13294427#comment-13294427
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Michael McCandless commented on LUCENE-4132:
--------------------------------------------
I dislike chaining ("return this" from setters) since it's so easily and often
abused. Here's an example from Lucene's tests:
{noformat}
IndexWriter w = new MockIndexWriter(dir, newIndexWriterConfig(
TEST_VERSION_CURRENT, new
MockAnalyzer(random())).setOpenMode(OpenMode.CREATE)
.setRAMBufferSizeMB(0.1).setMaxBufferedDocs(maxBufferedDocs).setIndexerThreadPool(new
ThreadAffinityDocumentsWriterThreadPool(maxThreadStates))
.setReaderPooling(doReaderPooling).setMergePolicy(newLogMergePolicy()));
{noformat}
bq. I don't quite understand what's the issue with the generics. If you don't
look at IWC / LC code, it's not visible at all. I mean, in your application
code, you won't see any generics.
It's also important to keep our non-user-facing sources simple too, so
our source code is approachable to new users.
Having 4 classes, plus generics, for what ought to be a simple
configuration class, is too much in my opinion. I'd rather stick with
javadocs explaining what can and cannot be changed live. This (wanting
to change live seettings) is expert usage...
Hopefully, we can simplify the approach here.
> 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
>
> Attachments: LUCENE-4132.patch
>
>
> 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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