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From: de Souza Medeiros Andre <andre.medeiros@aalto.fi>
To: "user@hbase.apache.org" <user@hbase.apache.org>
Subject: RE: HTable.getEndKeys() returning empty results
Thread-Topic: HTable.getEndKeys() returning empty results
Thread-Index: Acz9SAYLFo+KE3P3RaCnK/UmIMbmXf//5RGAgABUW6P///m+gIAA8ybOgAAHXps=
Date: Fri, 9 Mar 2012 10:29:05 +0000
Message-ID: <460ED1013765BD4A92CDA53C2082DCC68DD8D57C@EXMDB02.org.aalto.fi>
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Ok, now I'm not sure if I what I just said can be done.=0A=
=0A=
According to Lars George's book, in HBase "there are no index files that al=
low such direct access of a particular row or column.". Does this mean that=
 my scan "starting" at the given pointer will actually start scanning from =
the beginning of the block in HFile, ignoring everything until it scans the=
 row I specified as the start? =0A=
________________________________________=0A=
From: de Souza Medeiros Andre [andre.medeiros@aalto.fi]=0A=
Sent: Friday, March 09, 2012 12:02=0A=
To: user@hbase.apache.org=0A=
Subject: RE: HTable.getEndKeys() returning empty results=0A=
=0A=
Hi Drz,=0A=
=0A=
Yes, I've thought about that problem. But I've got an idea that sounds quit=
e ok. Since scanning seems to be the only way of getting the last data row =
of table A, one can implement a "counter" table (single row, single column)=
 to point to the row in A where the scanner should start. The counter value=
 can be periodically updated to improve the performance of scanners.=0A=
=0A=
Thanks for the support=0A=
=0A=
-- Andre Medeiros=0A=
________________________________________=0A=
From: Michael Drzal [mdrzal@gmail.com]=0A=
Sent: Thursday, March 08, 2012 23:28=0A=
To: user@hbase.apache.org=0A=
Subject: Re: HTable.getEndKeys() returning empty results=0A=
=0A=
On Thu, Mar 8, 2012 at 2:50 PM, de Souza Medeiros Andre <=0A=
andre.medeiros@aalto.fi> wrote:=0A=
=0A=
> Thanks for the answer.=0A=
> This is quite confusing though, what is the point of having a method to=
=0A=
> retrieve the last key if we know that anyway it will be an empty byte arr=
ay?=0A=
>=0A=
> Or does this happen only with one-region tables?=0A=
>=0A=
> Any way, is there some way of getting the last _data_ row of a table?=0A=
> Other than scanning the whole thing...=0A=
>=0A=
=0A=
Think about it this way:=0A=
=0A=
   - the last key for the region is key099=0A=
   - you insert key100=0A=
   - you insert key101=0A=
   - you insert key102=0A=
=0A=
Do you really want the meta table updated for each an every insert that=0A=
touches the end?=0A=
=0A=
  Drz=0A=
=0A=
=0A=
> Thanks,=0A=
> - Andre Medeiros=0A=
> ________________________________________=0A=
> From: saint.ack@gmail.com [saint.ack@gmail.com] on behalf of Stack [=0A=
> stack@duboce.net]=0A=
> Sent: Thursday, March 08, 2012 18:48=0A=
> To: user@hbase.apache.org=0A=
> Subject: Re: HTable.getEndKeys() returning empty results=0A=
>=0A=
> On Thu, Mar 8, 2012 at 8:25 AM, de Souza Medeiros Andre=0A=
> <andre.medeiros@aalto.fi> wrote:=0A=
> > Hi all,=0A=
> >=0A=
> > Has someone had problems with HTable.getEndKeys() method? In my=0A=
> application it returns an array of byte[], but the first (and only) byte[=
]=0A=
> is empty, so essentially it's telling me that the (single) region has no=
=0A=
> end key.=0A=
> >=0A=
> > The table has 3 rows and I'm running standalone HBase 0.90.4 CDH3u3 on=
=0A=
> my local machine. Moreover, the call getEndKeys() is executed immediately=
=0A=
> after I put rows in the table.=0A=
> >=0A=
> > Do I need to wait until the .META. table gets updated with the regions'=
=0A=
> end row keys?=0A=
> > Does HTable.getEndKeys() work only in a fully distributed mode?=0A=
> > Is there any other way of getting the last row in a table? (this is my=
=0A=
> objective after all)=0A=
> >=0A=
>=0A=
> An empty byte array is the last key in a table of one region only.  An=0A=
> hbase table uses empty byte array as both the start and end row=0A=
> signifier as per the bigtable paper (I don't see this explicitly=0A=
> called out in the reference guide but I'm probably not looking in=0A=
> right place).=0A=
>=0A=
> St.Ack=0A=
>=0A=