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HBase, mail # user - Using put for nullifying qualifiers


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Re: Using put for nullifying qualifiers
Kristoffer Sjögren 2012-05-23, 07:29
Ted: Awesome. I can think of several use cases where this is useful, but im
pretty stuck on 0.92 right now.

I tried the null-version trick but must be doing something wrong. How do I
set version to null on a column? Isnt version equal to the timestamp
(primitive long)?

Setting timestamp to 0 and -1 doesnt work it seems.

HTable t = new HTable(tablename);
Put p = new Put(r1);
KeyValue kv1 = new KeyValue(r1, c1, c1, new byte[]{1});
KeyValue kv2 = new KeyValue(r1, c2, c2, new byte[]{1});
p.add(kv1);
p.add(kv2);
t.put(p);
t.flushCommits();
Result res = t.get(new Get(r1));
byte[] v1 = res.getValue(c1, c1);
byte[] v2 = res.getValue(c2, c2);
System.out.println("v1 " + v1[0] + " v2 " + v2[0]);

kv1 = new KeyValue(r1, c1, c1, -1, new byte[]{1});
p = new Put(r1);
p.add(kv1);
t.put(p);
res = t.get(new Get(r1));
v1 = res.getValue(c1, c1);
v2 = res.getValue(c2, c2);
System.out.println("v1 " + v1[0] + " v2 " + v2[0]);

This prints:
v1 1 v2 1
v1 1 v2 1

Any advice?
On Tue, May 22, 2012 at 10:45 PM, Ted Yu <[EMAIL PROTECTED]> wrote:

> That's right.
>
> In HBase 0.94 and trunk, check out the following API in HRegion:
>  public void mutateRowsWithLocks(Collection<Mutation> mutations,
>      Collection<byte[]> rowsToLock) throws IOException {
>
> It allows you to combine Put's and Delete's for a single region,
> atomically.
>
> On Tue, May 22, 2012 at 1:22 PM, Kristoffer Sjögren <[EMAIL PROTECTED]
> >wrote:
>
> > Thanks, sounds like that should do it.
> >
> > So im guessing it is correct to assume that _all_ KeyValues added to a
> > _single_ Put operation will either wholely succeed or wholely fail as
> long
> > as they belong to the same row?
> >
> > On Tue, May 22, 2012 at 8:30 PM, Tom Brown <[EMAIL PROTECTED]> wrote:
> >
> > > I don't think you can include a delete with a put and keep it atomic.
> > > You could include a null version of the column with your put, though,
> > > for a similar effect.
> > >
> > > --Tom
> > >
> > > On Tue, May 22, 2012 at 10:55 AM, Kristoffer Sjögren <[EMAIL PROTECTED]
> >
> > > wrote:
> > > > Hi
> > > >
> > > > I'm trying to use Put operations to replace ("set") already existing
> > rows
> > > > by nullify certain columns and qualifiers as part of an Put
> operation.
> > > >
> > > > The reason I want to do this is 1) keep the operation
> atomic/consistent
> > > 2)
> > > > avoid latency from first doing Delete then Put.
> > > >
> > > > Is there some way to do this kind of operation?
> > > >
> > > > Cheers,
> > > > -Kristoffer
> > >
> >
>