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From "angela (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-4638) Mostly async unique index (for UUIDs for example)
Date Mon, 08 Aug 2016 06:27:20 GMT

    [ https://issues.apache.org/jira/browse/OAK-4638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15411382#comment-15411382
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angela commented on OAK-4638:
-----------------------------

Just one concern from my side: The security modules define some unique indices and where weakening
the uniqueness contract will have most severe security implications. In contrast the {{jcr:uuid}}
the synchronicity is not the biggest concern there (as long as applications don't write ugly
code with multiple sessions involved that ends up requiring the synchronous behavior).
This is different from the {{jcr:uuid}} which (for backwards compatibility) is also used for
the user/group lookup and where any kind of asynchronous indexing will lead to an escalation
nightmare because it will not only affect 'end-users' but also the application code itself
relying on system users.

> Mostly async unique index (for UUIDs for example)
> -------------------------------------------------
>
>                 Key: OAK-4638
>                 URL: https://issues.apache.org/jira/browse/OAK-4638
>             Project: Jackrabbit Oak
>          Issue Type: Improvement
>            Reporter: Thomas Mueller
>
> The UUID index takes a lot of space. For the UUID index, we should consider using mainly
an async index. This is possible because there are two types of UUIDs: those generated in
Oak, which are sure to be unique (no need to check), and those set in the application code,
for example by importing packages. For older nodes, an async index is sufficient, and a synchronous
index is only (temporarily) needed for imported nodes. For UUIDs, we could also change the
generation algorithm if needed.
> It might be possible to use a similar pattern for regular unique indexes as well: only
keep the added entries of the last 24 hours (for example) in a property index, and then move
entries to an async index which needs less space. That would slow down adding entries, as
two indexes need to be checked.



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