[ 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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