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From "Bryan Pendleton (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1559) when receiving a single EXTDTA object representing a BLOB, the server do not need to read it into memory before inserting it into the DB
Date Thu, 24 Aug 2006 06:50:11 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1559?page=comments#action_12430147 ] 
Bryan Pendleton commented on DERBY-1559:

Hi Andreas, I read your patch and I think it looks quite good. 

I worry about potentially losing valuable information from the DRDAProtocolException
instance when we catch it and transform it into an IOException.

Two possible ideas:
1) Use initCause() to embed the DRDAProtocolException into the IOException,
although maybe that's off limits because it's a 1.4 feature?
2) Before throwing the IOException, inside the catch block for the DRDAProtocolException,
log the full DRDAProtocolException somewhere. This might mean that when you
construct an EXTDTAReaderInputStream instance, you pass it some sort of
callback hook that gives it access to the Network Server's error log / console.

> when receiving a single EXTDTA object representing a BLOB, the server do not need to
read it into memory before inserting it into the DB
> ----------------------------------------------------------------------------------------------------------------------------------------
>                 Key: DERBY-1559
>                 URL: http://issues.apache.org/jira/browse/DERBY-1559
>             Project: Derby
>          Issue Type: Sub-task
>          Components: Network Server
>    Affects Versions:,,
>            Reporter: Andreas Korneliussen
>         Assigned To: Andreas Korneliussen
>         Attachments: DERBY-1559.diff, DERBY-1559.stat, DERBY-1559v2.diff, DERBY-1559v3.diff,
> When streaming a BLOB from the Network Client to the Network Server, the Network server
currently read all the data from the stream and put it into a byte array.
> The blob data is then inserted into the DB by using
> PreparedStatement.setBytes(..)
> and later
> PreparedStatement.execute()
> To avoid OutOfMemoryError if the size of the Blob is > than total memory in the VM,
we could make the network server create a stream which reads data when doing PreparedStatement.execute().
 The DB will then stream the BLOB data directly from the network inputstream into the disk.
> I intent to make a patch which does this if there is only one EXTDTA object (BLOB) sent
from the client in the statement, as it will simplify the implementation. Later this can be
improved  further to include CLOBs, and possibly to include the cases where there are multiple
EXTDTA objects.
> --
> CLOBs are more complex, as there need to be some character encoding. This can be achieved
by using a InputStreamReader,  and use PreparedStatement.setCharacterStream(..). However the
size of the stream is not necessarily the same as the size of the raw binary data, and to
do this for CLOBs, I would need the embedded prepared statements to support the new setCharacterStream()
overloads in JDBC4 (which do not include a length atribute)
> --
> Multiple EXTDATA objects are also more complex, since one would need to have fully read
the previous object ,before it is possible to read the next.
> --

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