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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-4520) Refactor and extend data type cloning facilities
Date Thu, 04 Feb 2010 19:14:28 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4520?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kristian Waagan updated DERBY-4520:
-----------------------------------

    Attachment: derby-4520-7a-lob_clonevalue_methods.diff

Patch 7a changes the cloneValue methods for SQLBlob and SQLClob.
The general idea for the character and binary values is that all streams are materialized
when cloning the value, expect for BLOB and CLOB. 
Note that BasicSortObserver is now forcing materialization of streams. This is how it used
to be (before patch 5a),  but I think this may cause problems for a few types of queries -
for instance 'select * from mytable order by length(myClob)'. This will have to be addressed
under a different Jira.

Also note that there are a few TODOs in the clone methods. I'd appreciate feedback on any
of these if you have something on your mind.

Regression tests passed (re-running as well to be sure).
Patch ready for review.

> Refactor and extend data type cloning facilities
> ------------------------------------------------
>
>                 Key: DERBY-4520
>                 URL: https://issues.apache.org/jira/browse/DERBY-4520
>             Project: Derby
>          Issue Type: Improvement
>          Components: Store
>    Affects Versions: 10.6.0.0
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>         Attachments: derby-4520-1a-RowLocation_cloning.diff, derby-4520-1a-RowLocation_cloning.diff,
derby-4520-2a-remove_CloneableObject_iface.diff, derby-4520-2a-remove_CloneableObject_iface.stat,
derby-4520-3a-CloneableStream_and_delayed_fill.diff, derby-4520-3a-CloneableStream_and_delayed_fill.stat,
derby-4520-3b-CloneableStream_and_delayed_fill.diff, derby-4520-3b-CloneableStream_and_delayed_fill.stat,
derby-4520-4a-cloneObject_renamed_cloneHolder.diff, derby-4520-5a-getClone_renamed_cloneValue.diff,
derby-4520-5a-getClone_renamed_cloneValue.stat, derby-4520-6a-unused_imports.diff, derby-4520-7a-lob_clonevalue_methods.diff
>
>
> With the increased use of streams to represent data values, the cloning facilities needs
to be improved.
> Unless I get pushback, I will proceed by producing patches to reach the following goals:
>  - move the functionality provided by CloneableObject into DataValueDescriptor
>    (all classes implementing CloneableObject also implements DataValueDescriptor)
>  - introduce the cloning methods cloneValue, cloneState and cloneHolder (all in DataValueDescriptor,
see description below)
>    Note that they all return a usable DVD. I'm all ears for better names for the clone
methods (another suggestion mentioned is cloneDeep, cloneHalfDeep, and cloneShallow).
> cloneValue <deep> (new method, functionality was present through combined calls
to the DVD public interface) 
>  - a DVD obtained through cloneValue is independent of other DVDs and the state of the
Derby store
>  - the data value will be materialized
> cloneState <halfDeep> (~= DataValueDescriptor.getClone)
>  - a DVD obtained through cloneState is independent of other DVDs, but may depend on
the state of the Derby store (due to references to store streams)
>  - the data value will be materialized if the value is represented by a non-cloneable
stream or if Derby believes materializing the value is more appropriate than keeping the stream
representation
> cloneHolder <shallow> (~= CloneableObject.cloneObject)
>  -  a DVD obtained through cloneHolder is dependent on the original DVD and its clones
made through cloneHolder. If one of the DVDs changes its state, all of them will be affected.
Will also be dependent on the state of the Derby store if there are references to store streams.
>  - the data value will never be materialized due to cloneHolder being invoked
> For many of the data types, cloneState and cloneHolder will forward to cloneValue.
> cloneState will be used the most. cloneValue is currently only required in the sorter.
cloneHolder is required (for performance reasons and maybe to avoid OOME) when DVDs pass through
temporary holders (BackingStoreHashtable, TemporaryRowHolderImpl). I have not gone through
all the usages of cloneState to see if any of them can be, or has to be, replaced with another
clone-call.
> The ability to clone store streams will be added by Mike's patch attached to DERBY-3650.

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