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Date: Mon, 11 Jun 2007 02:15:26 -0700 (PDT)
From: "Anurag Shekhar (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-2712) If large clob is updated after Reader.
 the reader continues to point to old data
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     [ https://issues.apache.org/jira/browse/DERBY-2712?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Anurag Shekhar updated DERBY-2712:
----------------------------------

    Attachment: derby-2712.diff

I have modified EmbedClob.getCharacterStream to return ClobUpdateableReader. ClobUpdateableReader is modifed to detect if the Clob has moved from Readonly InternalClob to a writable InternalClob. If the EmbedClob moves from readonly mode to writable mode it fetches the input stream again from the EmbedClob and skips to the current position.
Code to invalidate the internal Reader in case the underlying stream is modified was already part of this Reader.

Updated files
java/engine/org/apache/derby/impl/jdbc/EmbedClob.java
Added two methods
	isWritable
		ClobUpdateableReader uses this methods to determine if the Clob has swtched from a readonly InternalClob to a writable InternalClob.
	getInternalStream
		ClobUpdateableReader uses this method if it detects Clob is modified since creating ClobUpdateableReader.
	
Modified getCharacterStream() to return ClobUpdateableReader.

java/engine/org/apache/derby/impl/jdbc/ClobUpdateableReader.java

added a new constructor. This constructor will be used by EmbedClob. It accepts Clob as a parameter Clob object is used to check if the InternalClob its using is writable or not. In case it was read only in the begning ClobUpdateableReader uses getInternalStream to refresh the stream after it switches to writable InternalClob.

Added a new private method updateIfRequired which is called in every method to check if the underlying stream has changed.

java/testing/org/apache/derbyTesting/functionTests/tests/jdbcapi/ClobUpdateableReaderTest.java

Added a new test for switching from StoreStream to ClobStreamControl.


> If large clob is updated after Reader. the reader continues to point to old data
> --------------------------------------------------------------------------------
>
>                 Key: DERBY-2712
>                 URL: https://issues.apache.org/jira/browse/DERBY-2712
>             Project: Derby
>          Issue Type: Bug
>          Components: JDBC
>    Affects Versions: 10.3.0.0
>            Reporter: Anurag Shekhar
>         Attachments: derby-2712.diff
>
>
> If a Reader is fetched from a large clob (obtained from ResultSet) a reader linked to the dvd stream is returned once a set method is called on it the clob data is materialized in control class but the Reader returned previously continues to point to old data.

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