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From Jonathan Gray <jl...@streamy.com>
Subject Re: Question/Suggestion: obtaining older versions of values
Date Mon, 26 Oct 2009 16:12:50 GMT
Personally, when I need to dig into a complex result with multiple 
columns and versions, I iterate over the KeyValues directly rather than 
messing with the Map-based return formats from Result.

In your example, are you just returning versions/values for a single 
column?  Maybe we could add some methods that returned subsets of the 
total set of KeyValues (for example, Result.getKeyValues(family, 
qualifier) would return all versions of that column in the result in 
KeyValue format).

Going to drop a note in HBASE-1937.

JG

Doug Meil wrote:
> Hi there-
> 
> Question:  how does one obtain older versions of values from Result?
> 
> As I understand it, the following Scan instance should return the last 5 versions of
values for a table, provided that the table is versioned.
> 
>     Scan scan = new Scan();
>     scan.setMaxVersions(5);
> 
>>>From the Javadoc, it looks like what I want is in here (from Result)....
> getMap
> 
> public NavigableMap<http://java.sun.com/javase/6/docs/api/java/util/NavigableMap.html?is-external=true><byte[],NavigableMap<http://java.sun.com/javase/6/docs/api/java/util/NavigableMap.html?is-external=true><byte[],NavigableMap<http://java.sun.com/javase/6/docs/api/java/util/NavigableMap.html?is-external=true><Long<http://java.sun.com/javase/6/docs/api/java/lang/Long.html?is-external=true>,byte[]>>>
getMap()
> Map of families to all versions of its qualifiers and values.
> 
> ...  but there is a fair amount of gymnastics involved to get the data.
> 
> Suggestion:   can an example of iterating over this map (and contained maps) be added
to the Javadoc?  Versioning is a powerful feature of HBase but using it isn't obvious in result
processing.
> 
> Thanks!
> 
> 
> Doug Meil
> Director of Engineering
> doug.meil@explorys.net
> 
> 

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