Hi Dan,
Only thing I saw extra from the logs was:
2009-01-29 08:02:46,077 DEBUG
virtualdatabase.VirtualDatabaseWorkerThread.myDb statementExecute
command
If that's what I was supposed to get, I am not sure what it means to
you.
Well it just means that Sequoia has to figure out by itself whether it
has to broadcast that call or not. This is just a different path in the
Sequoia code but that should not affect the way the result is fetched.
Now, for a backend object converter. No sure what you mean but I am
going to guess it's something you can plug into Sequoia so that it
changes how it uses one of the backend databases. Does such a thing
already exist for Postgres? I can imagine if it didn't it would cause
problems if you were using Postgres alongside a different DB type in a
cluster as calls getting binary data would act different unless such a
thing existed. And if that is true... why isn't the default behavior to
do that? Sequoia seems to detect that it is dealing with Postgres
(unless I miss read the log).
If such a thing doesn't already exist, is there a place with some
documentation on how to make one?
Well, Robert announced that Continuent would release the uni/cluster
source code and this includes a BackendObjectConverter for Postgres. The
problem is that we don't know when this is going to happen.
Now, Sequoia does not really detect that the database is Postgres, it
just reports what the database driver says. Sequoia 4 will have that
capacity to enforce pre-defined database specific extensions at the
virtual database level (instead of at the controller level in Sequoia
2.10). Here is how you can modify the existing
SequoiaBackendObjectConverter in package
org.continuent.sequoia.controller.backend. There is a single function
that is defined as follows:
public Object convertResultSetObject(ResultSet dbResultSet, int i,
Field f)
throws SQLException
{
Object object = dbResultSet.getObject(i + 1);
return object;
}
You have to test if the field is an oid and then call getBlob instead of
getObject. Something like this would do:
public Object convertResultSetObject(ResultSet dbResultSet, int i,
Field f)
throws SQLException
{
Object object;
if (field.getTypeName().equals("oid"))
object = dbResultSet.getBlob(i + 1);
else
object = dbResultSet.getObject(i + 1);
return object;
}
Let me know if that works for you,
Emmanuel
Thanks,
Dan McFadyen
-----Original Message-----
From: [email protected] [mailto:sequoia-
[email protected]] On Behalf Of Emmanuel Cecchet
Sent: January 28, 2009 3:05 PM
To: Sequoia general mailing list
Subject: Re: [Sequoia] Getting binary data from a postgres backend
Dan,
Sequoia ships with isql (look in the bin/ directory) that is a Java
client. You could check if you can retrieve all your data with isql.
Another thing you can do is set the
log4j.logger.org.continuent.sequoia.controller.virtualdatabase.VirtualD
atabaseWorkerThread
logger to DEBUG in config/log4j.properties, it should tell you what
kind
of call is will perform.
A caveat with Postgres is that Sequoia fetches ResultSets using
getObject which might return an oid instead of the data. If this is
the
case, you need to use a special backend object converter that will
call
getBlob instead of getObject.
Let us know what you see in the trace when you run with the logger set
to DEBUG.
Thanks,
Emmanuel
--
Emmanuel Cecchet
FTO @ Frog Thinker
Open Source Development & Consulting
--
Web: http://www.frogthinker.org
email: [email protected]
Skype: emmanuel_cecchet
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--
Emmanuel Cecchet
FTO @ Frog Thinker
Open Source Development & Consulting
--
Web: http://www.frogthinker.org
email: [email protected]
Skype: emmanuel_cecchet
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