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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2763) In the Network Client InputStreams and Readers returned from LOB's should be sensitive to underlying LOB data changes.
Date Tue, 12 Jun 2007 16:12:28 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12503899
] 

Rick Hillegas commented on DERBY-2763:
--------------------------------------

Thanks for the patch, Narayanan. I am reading it now. Here is an initial reaction:

It seems to me that the input stream's position is an offset from the start of the LOB. When
the stream is recreated, the current position (offset from the start of the LOB) does not
change. So it seems to me that Øystein's use-case is supported if the rewritten chunks do
not change size. So, I am puzzled. To support that use case, is there any need to recreate
the streams? It appears to me that the recreation of the streams supports some other use-case,
in which the writer is writing bytes further on in the LOB, and not in the porition that has
already been read.

Do we have a use-case in mind for this scenario? It would be nice to be able to argue to ourselves
that we are building something that solves a customer problem here.


> In the Network Client InputStreams and Readers returned from LOB's should be sensitive
to underlying LOB data changes.
> ----------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-2763
>                 URL: https://issues.apache.org/jira/browse/DERBY-2763
>             Project: Derby
>          Issue Type: Bug
>          Components: Network Client
>    Affects Versions: 10.3.0.0
>            Reporter: V.Narayanan
>            Assignee: V.Narayanan
>             Fix For: 10.3.0.0
>
>         Attachments: Approach_2.diff, Approach_2.stat, Approach_2.txt, Approach_3.diff,
Approach_3.stat, Approach_4.diff, Approach_4.stat, LOBLengthPersists.java, UpdateSensitiveStreamsForClient_v1.diff,
UpdateSensitiveStreamsForClient_v1.stat
>
>
> Currently the Embedded and Network Client would differ 
> in behaviour when the following series of steps is 
> followed.
> a) Create an empty Blob
> b) get an InputStream using Blob.getBinaryStream()
> c) write data into this Blob
>    c.1) Get an OutputStream
>    c.2) Use OutputStream.write(byte [] b) to write
>         into this Blob.
> d) Now read from the InputStream obtained in step b)
>    and print the number of bytes read as output.
> The output of step d) differs in the client and in the Embedded side.
> In the Client
> -------------
> The number of bytes read would always be -1.
> In the Embedded
> ---------------
> The number of bytes would be the number of bytes we
> reflected.
> The above behaviour in the NetworkClient is because
> the length of the Blob is read once and stored in the 
> constructor of the locator Stream returned (in the 
> attribute maxPos).
> This instead should be read each time we use the streams.
> A similar issue exists for Clobs also.
> I will raise a seperate JIRA issue for this.

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