Hi Jonathan, The use-case in question is one column with multiple versions, either to table-display or plot (Y values over X timestamps), and since the insertion time into HBase is good enough for the X dimension, we don't need a second column.
After digging through my test program per your suggestion, I realized the error of my ways. The history *does* actually come back with the KeyValues when requested. Doh! I was so focused on this Javadoc comment from getMap() "Map of families to all versions of its qualifiers and values." that I focused on that method instead of realizing that the data was right in front of me with KeyValue. I do think that something like what you suggested "Result.getKeyValues(family, qualifier)" would still be useful for other versioned use-cases. I'd still suggest a few blurbs in the Result Javadoc on obtaining history (and that the methods that return KeyValues contain history when requested). It's "obvious" now that I understand it, but not so obvious from the existing Javadoc. I'd be happy to help out with some of this documentation. Thanks! -----Original Message----- From: Jonathan Gray [mailto:[email protected]] Sent: Monday, October 26, 2009 12:13 PM To: [email protected] Subject: Re: Question/Suggestion: obtaining older versions of values 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 > [email protected] > >
