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https://issues.apache.org/jira/browse/LUCENE-1052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12544125
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Doug Cutting commented on LUCENE-1052:
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What class would we put TermInfosReader-specific setters & getters on, since
that class is not public? Do we make TermInfosReader public or leave it
package-private? My intuition is to leave it package-private for now, in order
to retain freedom to re-structure w/o breaking applications, and because making
it public would drag a lot of other stuff into the public. We could consider
making SegmentReader public, so that there's a public class that corresponds to
the concrete index implementation, but that'd also drag more stuff public (like
DirectoryIndexReader).
I'm also not yet convinced that it is critical to support arbitrary formulae
for this feature. Sure, it would be nice, but it has costs, like increasing
public APIs that must be supported. Folks have done fine without this feature
for many years. Adding a simple integer divisor is a sufficient initial step
here.
So, even if we add a configuration system, I think the setter methods could
still end up on IndexReader. The difference is primarily whether the methods
are:
public void setTermIndexInterval(int interval);
public void setTermIndexDivisor(int divisor);
or
public static void setTermIndexInterval(LuceneProps props, int interval);
public static void setTermIndexDivisor(LuceneProps props, int divisor);
With the latter just a façade that uses package-private stuff. I think the
latter style will be handy as we start adding parameters to, e.g., Query
classes. In those cases we'll probably want façade's too, since a Query setter
will probably really tweak something for a private Scorer class. In the case
of indexes, however, we don't have a public, concrete class.
Another option is to make a public class whose purpose is just to only such
parameters, something like SegmentIndexParameters. That'd be my first choice
and was the direction I pointed in my initial proposal, but with considerably
less explanation.
> Add an "termInfosIndexDivisor" to IndexReader
> ---------------------------------------------
>
> Key: LUCENE-1052
> URL: https://issues.apache.org/jira/browse/LUCENE-1052
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: 2.2
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Priority: Minor
> Fix For: 2.3
>
> Attachments: LUCENE-1052.patch, termInfosConfigurer.patch
>
>
> The termIndexInterval, set during indexing time, let's you tradeoff
> how much RAM is used by a reader to load the indexed terms vs cost of
> seeking to the specific term you want to load.
> But the downside is you must set it at indexing time.
> This issue adds an indexDivisor to TermInfosReader so that on opening
> a reader you could further sub-sample the the termIndexInterval to use
> less RAM. EG a setting of 2 means every 2 * termIndexInterval is
> loaded into RAM.
> This is particularly useful if your index has a great many terms (eg
> you accidentally indexed binary terms).
> Spinoff from this thread:
> http://www.gossamer-threads.com/lists/lucene/java-dev/54371
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