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From "Karthick Sankarachary (JIRA)" <>
Subject [jira] Updated: (LUCENE-2429) A Rotating Split Policy For Managing Bounded Indices
Date Sun, 02 May 2010 16:12:55 GMT


Karthick Sankarachary updated LUCENE-2429:

    Attachment: LUCENE-2429.patch

> A Rotating Split Policy For Managing Bounded Indices
> ----------------------------------------------------
>                 Key: LUCENE-2429
>                 URL:
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: contrib/*, Index
>    Affects Versions: 3.0.1
>            Reporter: Karthick Sankarachary
>         Attachments: LUCENE-2429.patch
> (Please note that the feature described in LUCENE-2425 is required reading for this issue.)
> A rotating split policy maintains a bounded set of sub-indices underneath the split index's
directory. The motivation for such a policy is to be able to control the size of the index
in a user-defined manner. It comes in handy in scenarios where (a) documents are added at
a higher-than-normal rate, and (b) documents older than a certain cut-off date needn't be
searchable. As a matter of fact, this policy is applicable to most real-time streams, given
that they tend to satisfy both of the above properties.
> In short, when the number of sub-indices hits the maximum allowed number (@see {@link
ROTATING_POLICY_MAXIMUM_SUB_INDICES}), then this policy effectively forces the last sub-index
out of the split index. A sub-index is deemed to be the last one if it is considered to be
lesser (according to #getDirectoryComparator) than every other sub-index.
> The exact point in time at which rotation occurs is determined by the split rule(s) in
effect for this policy. For example, one may apply a scheduled split rule (see LUCENE-2427)
if one wishes the split to occur at fixed intervals. For finer control over the periodicity
of the interval, a cron split rule (see LUCENE-2428) may be employed.
> To illustrate the behavior of the rotation policy policy, consider a split rule that
triggers a split on the hour every hour. Furthermore, let's assume that the maximum number
of sub-indices allowed is 7. In this case, the rotation policy will have no more than 8 hours
worth of data (1 hour in the super-index and each of the 7 sub-indices).

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