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From "Andreas Korneliussen (JIRA)" <derby-...@db.apache.org>
Subject [jira] Updated: (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, 27 Jul 2006 14:28:16 GMT
     [ http://issues.apache.org/jira/browse/DERBY-1559?page=all ]

Andreas Korneliussen updated DERBY-1559:
----------------------------------------

    Attachment: DERBY-1559.diff
                DERBY-1559.stat

Attached is a patch which does the following:

EXTDTAReaderInputStream: this is a new class which is a subclass of InputStream. It is capable
of reading EXTDTA from the network using the DDMReader.

DDMReader: added helper methods to create EXTDTAReaderInputStream and to let it fetch more
data

DRDAConnThread: 
* When handling a EXCSQLSTT request DRDAConnThread will do an execute of the statement right
after calling readAndSetAllExtParams(..). This is because the call to stmt.execute() will
start the stream of the LOB data.  readAndSetExtParam (..) is implemented so that it will
only do streaming of LOB on the last EXTDTA parameter, otherwise it will use the old mechanism
of streaming all and creating a byte-array. 

Using this patch, I have successfully inserted a 1GB blob streamed from the Network client
to the Network server, running the Network server with 64MB of max heap space. I have also
run derbyall with this patch, with no failures.


> 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: 10.2.0.0
>            Reporter: Andreas Korneliussen
>         Assigned To: Andreas Korneliussen
>         Attachments: DERBY-1559.diff, DERBY-1559.stat
>
>
> 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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