Re: Change column family

[shweta.agrawal]

Thanks for all the suggestion.

I read about TransformingIterator and started implementing it,  I 
extended this class and tried to override its abstract method. But I am 
not able to get where and what to write to change column family?

So please provide your suggestions.

Thanks
Shweta


On Tuesday 26 May 2015 08:33 PM, Adam Fuchs wrote:
This can also be done with a row-doesn't-fit-into-memory constraint. 
You won't need to hold the second column in-memory if your iterator 
tree deep copies, filters, transforms and merges. Exhibit A:

[HeapIterator-derivative]
 |_________________________
   |     \
[transform-graph1-to-graph2]  \
   |       \
[column-family-graph1][all-but-column-family-graph1]

With this design, you can subclass the HeapIterator, deep copy the 
source in the init method, wrap one in a custom transform iterator, 
and create a appropriate seek method. This is probably more on the 
advanced side of Accumulo programming, but can be done.

Adam


On Tue, May 26, 2015 at 8:59 AM, Eric Newton <eric.new...@gmail.com 
<mailto:eric.new...@gmail.com>> wrote:

    Short answer: no.

    Long answer: maybe.

    You can write an iterator which will transform:

    row, cf1, cq, vis -> value

    into:

    row, cf2, cq, vis -> value

    And if you can do this while maintaining sort order, you can get
    your new ColumnFamily transformed during scans and compactions.

    But this bit about maintaining the sort order is more complex than
    it sounds.

    If you have the following:

    row, a, cq, vis -> value
    row, aa, cq, vis -> value


    And you want to transform cf "a" into cf "b":

    row, aa, cq, vis -> value
    row, b, cq, vis -> value


    Your iterator needs to hold the second column in memory, after
    transforming the first column.  Tablet server memory for holding
    Key/Values is not infinite.

    -Eric

    On Tue, May 26, 2015 at 8:44 AM, shweta.agrawal
    <shweta.agra...@orkash.com <mailto:shweta.agra...@orkash.com>> wrote:

        Hi,

        I want to ask, is it possible in accumulo to change the column
        family without changing the whole data.

        Suppose my column family is graph1, now i want to rename this
        column family as graph2.
        Is it possible?

        Thanks
        Shweta