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From "Thomas Mueller (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-1941) RDB: decide on table layout
Date Wed, 03 Dec 2014 07:24:12 GMT

    [ https://issues.apache.org/jira/browse/OAK-1941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14232709#comment-14232709
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Thomas Mueller commented on OAK-1941:
-------------------------------------

I wonder, how common is it (do we have statistics) that we have the correct old document before
an update? If this is a 99% case, then I think we could avoid the read operation, and just
rely on the update count.

> RDB: decide on table layout
> ---------------------------
>
>                 Key: OAK-1941
>                 URL: https://issues.apache.org/jira/browse/OAK-1941
>             Project: Jackrabbit Oak
>          Issue Type: Sub-task
>          Components: rdbmk
>            Reporter: Julian Reschke
>            Assignee: Julian Reschke
>             Fix For: 1.2
>
>         Attachments: OAK-1941-cmodcount.diff, utf8measure.diff, with-modified-index.diff
>
>
> The current approach is to serialize the Document using JSON, and then to store either
(a) the full JSON in a VARCHAR column, or, if that column isn't wide enough, (b) to store
it in a BLOB (optionally gzipped).
> For debugging purposes, the inline VARCHAR always gets populated with the start of the
JSON serialization.
> However, with Oracle we are limited to 4000 bytes (which may be way less characters due
to non-ASCII overhead), so many document instances will use what was initially thought to
be the exception case.
> Questions:
> 1) Do we stick with JSON or do we attempt a different serialization? It might make sense
both wrt to length and performance. There might be also some code to borrow from the off-heap
serialization code.
> 2) Do we get rid of the "dual" strategy, and just always use the BLOB? The indirection
might make things more expensive, but then the total column width would drop considerably.
-- How can we do good benchmarks on this?
> (This all assumes that we stick with a model where all code is the same between database
types, except for the DDL statements; of course it's also conceivable add more vendor-specific
special cases into the Java code)



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