Bob Durie wrote:
Hi,
I’ve searched for this issue on jira with no luck, posting here in hopes
someone has seen it or knows where it might be coming from.
What I’m seeing is that “sometimes” during a schema upgrade of our
database, the getImportedKeys or getPrimaryKeys methods of
EmbedDatabaseMetaData fail with syntax errors (see the stack trace
below). If we rollback the transaction, try again, it is ALWAYS
successful, but may fail later on when we do a similar operation with
another table. Hence, we have a workaround (try again), but it doesn’t
leave me feeling very confident.
[snip]
One thing to note is that the process in our application calls the
“connection.getMetaData” many many times, makes updates to the schema,
and calls it again many times on the same transaction. While not
necessarily efficient, I’m reluctant to change it as I want to know the
source of the problem first.
I think it's a bug in Derby. The metadata queries use some internal SQL
constructs and are compiled in "internal SQL" mode to allow these
constructs. It looks like something is triggering a re-compile of the
metadata statement at runtime and during this re-compile the internal
SQL flag is not set.
I'm not sure what you could be doing that results in the recompile, one
possibility is a rollback in a transaction that performed some DDL.
Somthing like:
begin tran
ddl
execute meta data for first time
rollback
Derby at the moment is fairly liberal in its statement invalidation when
a rollback happens in a transaction that performed DDL, assuming that
this is a infrequent and non-performance critical event.
Dan.
