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https://issues.apache.org/jira/browse/DERBY-1107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12645807#action_12645807
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Knut Anders Hatlen commented on DERBY-1107:
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It sounds safe to me too, as long as we only do this for 10.5 and higher. I
don't think the time to boot on version change is a big issue, and the code
will be more robust if we recreate the SPSs on version change.
With this patch, will they be recreated on every version change, or only when
one of the first three digits in the version number changes? That is, will they
get recreated when we move from 10.5.1.0 to 10.5.1.1? I'm getting a bit
confused by the naming in DD_Version, since it seems to use major/minor version
in a different way than we normally do.
> For existing databases JDBC metadata queries do not get updated properly
> between maintenance versions.
> -------------------------------------------------------------------------------------------------------
>
> Key: DERBY-1107
> URL: https://issues.apache.org/jira/browse/DERBY-1107
> Project: Derby
> Issue Type: Bug
> Components: JDBC
> Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.2.1, 10.1.3.1,
> 10.2.1.6
> Reporter: Kathey Marsden
> Assignee: Kathey Marsden
> Attachments: derby-1107-proposal1.diff, derby-1107_diff.txt,
> derby-1107_diff2.txt, derby-1107_noproc_diff.txt
>
>
> The JDBC DatabaseMetaData queries are stored as stored prepared statements in
> the database. If a bug is fixed for any of the metadata calls it can
> require that these queries be changed. Currently existing databases will
> not get updated properly if a bug is fixed. Ideally the metadata queries
> should match the derby version that is running. That way we avoid situations
> where the query is not compatible with the Derby version running.
> To confirm I :
> 1) created a database with 10.1.1.0
> 2) Made a metadata change in my 10.1.2.4 client.
> 3) Connected to the 10.1.1.0 database with 10.1.2.4 and saw that there was no
> change to the stored prepared statements in SYS.SYSSTATEMENTS
> I also confirmed that a database created with 10.1.2.4 does not get changed
> when reverting to 10.1.1.0.
> Below this line is some history and reference that might be helful to someone
> fixing this issue:
> ------------------------------------------------------------------------------------------------------------------------------------------------
> In discussing DERBY-970, the subject of the metadata stored prepared
> statements
> came up.
> The general questions are:
> 1) Why do we use stored prepared statements for metadata queries?
> 2) What issues might there be related to upgrade/downgrade with the
> metadata stored prepared statements?
> 3) How do we address potential upgrade/downgrade issues?
>
> GENERAL HISTORY:
> - Cloudscape 5.x had stored prepared statements, a way to store precompiled
> statements in the database. This is no longer exposed externally.
> - Metadata stored prepared statements were a performance optimization that
> predated the statement cache.
> - In the past, this performance optimization has been of particular
> importance
> to gui database browsers that execute all the metadata methods on connection
> to
> the database. This would still probably be an issue with embedded even with
> the
> statement cache.
> - All stored prepared statements get recompiled on the first connection to
> the
> database if the version changes.
> UPGRADE HISTORY
> - In Cloudscape 5.1, the metadata stored prepared statements have
> traditionally
> been a source of trouble for even minor version changes as queries change or
> they refer to methods/stored procedures that may or may not exist in the
> target
> version and cannot recompile or execute.
> - The solution to the problem in Cloudscape v5.1.60 was to automatically
> always call DD_Version.dropJDBCMetadataSPSes() whenever the version changed
> up
> or down in upgradeIfNeeded().
> - The workaround before this change to do this automatically was to call this
> method manually:
> | CALL Factory.getDatabaseOfConnection().
> dropAllJDBCMetaDataSPSes()|
> HOW DERBY WORKS TODAY:
> - In Derby we now only call dropJDBCMetadataSPSes() on fullUpgrade and it
> has
> been this way since contribution.
> - I think the problems of upgrade/downgrade for metadata stored prepared
> statements may exist in Derby.
> - I don't know a workaround to drop the metadata stored prepared statements
> if
> we need to deliver a bug fix or how the ugprade/downgrade is handled
> currently.
> - I seem to recall some special handling in Derby for soft upgrade for
> optimizer directives, but don't know the details.
> RECENT DISCUSSIONS:
> In discussing DERBY-970, the subject of the metadata stored prepared
> statements
> came up.
> The general questions are:
> 1) Why do we use stored prepared statements for metadata queries?
> 2) What issues might there be related to upgrade/downgrade with the
> metadata stored prepared statements?
> 3) How do we address potential upgrade/downgrade issues?
>
> MY QUESTIONS
> Anyone know when/why the dropJDBCMetadataSPSes() on all version changes was
> removed between Cloudcape 5.1.60 and contribution?
> How do we deliver bug fixes for metadata queries or handle changes in the
> metadata queries in Derby?
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