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From Thomas Vandahl ...@apache.org>
Subject MetaData caching in Village
Date Wed, 11 Aug 2010 18:40:26 GMT
Hi folks,

I'm currently trying to fix that long outstanding problem of excessive
meta-data access in Village. I find that I could need some net.wisdom.
So if someone could try to reproduce/confirm my thoughts I'd be grateful.

- The problem is most probably in Column.populate()
- Obviously, some caching takes place in Schema, but it doesn't work for
QueryDataSets, just for DataSets and TableDataSets
- I found a hint that it is better to fetch the ResultMetaData from a
prepared statement that is just prepared but not executed.
- Would it be "legal" to create a PreparedStatement on a connection that
has other statements/resultsets open?
- I'd like to use the existing caching mechanism, which creates Schema
objects from "select * from tablename". Would that cover aliased
columns, too?
- If I don't want to introduce additional dependencies, the lifetime of
the cache (being a Hashtable) would be the lifetime of the JVM. Some
ideas for orderly shutdown/invalidation would be helpful.
- Would someone be willing to verify my fixes against different
databases, namely Sybase, MS-SQL and Oracle?

Thanks in advance.

Bye, Thomas

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