HBase, mail # user - Fastest way to read only the keys of a HTable?

Fastest way to read only the keys of a HTable?

Something Something 2011-02-03, 06:01

I want to read only the keys in a table. I tried this...

try {

HTable table = new HTable("myTable");

Scan scan = new Scan();

scan.addFamily(Bytes.toBytes("Info"));

ResultScanner scanner = table.getScanner(scan);

Result result = scanner.next();

while (result != null) {

& so on...

This was performing fairly well until I added another Family that contains
lots of key/value pairs. My understanding was that adding another family
wouldn't affect performance of this code because I am explicitly using
"Info", but it is.

Anyway, in this particular use case, I only care about the "Key" of the row.
I don't need any values from any of the families. What's the best way to
do this?

Please let me know. Thanks.

Re: Fastest way to read only the keys of a HTable?

Stack 2011-02-03, 06:20

See http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FirstKeyOnlyFilter.html
St.Ack

On Thu, Feb 3, 2011 at 6:01 AM, Something Something
<[EMAIL PROTECTED]> wrote:
> I want to read only the keys in a table. I tried this...
>
> try {
>
> HTable table = new HTable("myTable");
>
> Scan scan = new Scan();
>
> scan.addFamily(Bytes.toBytes("Info"));
>
> ResultScanner scanner = table.getScanner(scan);
>
> Result result = scanner.next();
>
> while (result != null) {
>
> & so on...
>
> This was performing fairly well until I added another Family that contains
> lots of key/value pairs. My understanding was that adding another family
> wouldn't affect performance of this code because I am explicitly using
> "Info", but it is.
>
> Anyway, in this particular use case, I only care about the "Key" of the row.
> I don't need any values from any of the families. What's the best way to
> do this?
>
> Please let me know. Thanks.
>

Re: Fastest way to read only the keys of a HTable?

Something Something 2011-02-03, 06:47

Thanks. So I will add this...

scan.setFilter(new FirstKeyOnlyFilter());

But after I do this...

Result result = scanner.next();

There's no... result.getKey() - so what method would give me the Key value?

On Wed, Feb 2, 2011 at 10:20 PM, Stack <[EMAIL PROTECTED]> wrote:

> See
> http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FirstKeyOnlyFilter.html
> St.Ack
>
> On Thu, Feb 3, 2011 at 6:01 AM, Something Something
> <[EMAIL PROTECTED]> wrote:
> > I want to read only the keys in a table. I tried this...
> >
> > try {
> >
> > HTable table = new HTable("myTable");
> >
> > Scan scan = new Scan();
> >
> > scan.addFamily(Bytes.toBytes("Info"));
> >
> > ResultScanner scanner = table.getScanner(scan);
> >
> > Result result = scanner.next();
> >
> > while (result != null) {
> >
> > & so on...
> >
> > This was performing fairly well until I added another Family that
> contains
> > lots of key/value pairs. My understanding was that adding another family
> > wouldn't affect performance of this code because I am explicitly using
> > "Info", but it is.
> >
> > Anyway, in this particular use case, I only care about the "Key" of the
> row.
> > I don't need any values from any of the families. What's the best way
> to
> > do this?
> >
> > Please let me know. Thanks.
> >
>

Re: Fastest way to read only the keys of a HTable?

Stack 2011-02-03, 06:55

I don't see a getKey on Result. Use
http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Result.html#getRow().

Here is how its used in the shell table.rb class:

   # Count rows in a table
   def count(interval = 1000, caching_rows = 10)
   # We can safely set scanner caching with the first key only filter
   scan = org.apache.hadoop.hbase.client.Scan.new
   scan.cache_blocks = false
   scan.caching = caching_rows
   scan.setFilter(org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter.new)

   # Run the scanner
   scanner = @table.getScanner(scan)
   count = 0
   iter = scanner.iterator

   # Iterate results
   while iter.hasNext
   row = iter.next
   count += 1
   next unless (block_given? && count % interval == 0)
   # Allow command modules to visualize counting process
   yield(count, String.from_java_bytes(row.getRow))
   end

   # Return the counter
   return count
   end
St.Ack

On Thu, Feb 3, 2011 at 6:47 AM, Something Something
<[EMAIL PROTECTED]> wrote:
> Thanks. So I will add this...
>
> scan.setFilter(new FirstKeyOnlyFilter());
>
> But after I do this...
>
> Result result = scanner.next();
>
> There's no... result.getKey() - so what method would give me the Key value?
>
>
>
> On Wed, Feb 2, 2011 at 10:20 PM, Stack <[EMAIL PROTECTED]> wrote:
>
>> See
>> http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FirstKeyOnlyFilter.html
>> St.Ack
>>
>> On Thu, Feb 3, 2011 at 6:01 AM, Something Something
>> <[EMAIL PROTECTED]> wrote:
>> > I want to read only the keys in a table. I tried this...
>> >
>> > try {
>> >
>> > HTable table = new HTable("myTable");
>> >
>> > Scan scan = new Scan();
>> >
>> > scan.addFamily(Bytes.toBytes("Info"));
>> >
>> > ResultScanner scanner = table.getScanner(scan);
>> >
>> > Result result = scanner.next();
>> >
>> > while (result != null) {
>> >
>> > & so on...
>> >
>> > This was performing fairly well until I added another Family that
>> contains
>> > lots of key/value pairs. My understanding was that adding another family
>> > wouldn't affect performance of this code because I am explicitly using
>> > "Info", but it is.
>> >
>> > Anyway, in this particular use case, I only care about the "Key" of the
>> row.
>> > I don't need any values from any of the families. What's the best way
>> to
>> > do this?
>> >
>> > Please let me know. Thanks.
>> >
>>
>

Re: Fastest way to read only the keys of a HTable?

Something Something 2011-02-03, 19:27

Hmm.. performance hasn't improved at all. Do you see anything wrong with
the following code:
   public List<Partner> getPartners() {
   ArrayList<Partner> partners = new ArrayList<Partner>();

   try {
   HTable table = new HTable("partner");
   Scan scan = new Scan();
   scan.setFilter(new FirstKeyOnlyFilter());
   ResultScanner scanner = table.getScanner(scan);
   Result result = scanner.next();
   while (result != null) {
   Partner partner = new
Partner(Bytes.toString(result.getRow()));
   partners.add(partner);
   result = scanner.next();
   }
   } catch (IOException e) {
   throw new RuntimeException(e);
   }
   return partners;
  }

May be I shouldn't use more than one "column family" in a HTable - but the
BigTable paper recommends that, doesn't it? Please advice and thanks for
your help.
On Wed, Feb 2, 2011 at 10:55 PM, Stack <[EMAIL PROTECTED]> wrote:

> I don't see a getKey on Result. Use
>
> http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Result.html#getRow()
> .
>
> Here is how its used in the shell table.rb class:
>
> # Count rows in a table
> def count(interval = 1000, caching_rows = 10)
> # We can safely set scanner caching with the first key only filter
> scan = org.apache.hadoop.hbase.client.Scan.new
> scan.cache_blocks = false
> scan.caching = caching_rows
> scan.setFilter(org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter.new)
>
> # Run the scanner
> scanner = @table.getScanner(scan)
> count = 0
> iter = scanner.iterator
>
> # Iterate results
> while iter.hasNext
> row = iter.next
> count += 1
> next unless (block_given? && count % interval == 0)
> # Allow command modules to visualize counting process
> yield(count, String.from_java_bytes(row.getRow))
> end
>
> # Return the counter
> return count
> end
>
>
> St.Ack
>
> On Thu, Feb 3, 2011 at 6:47 AM, Something Something
> <[EMAIL PROTECTED]> wrote:
> > Thanks. So I will add this...
> >
> > scan.setFilter(new FirstKeyOnlyFilter());
> >
> > But after I do this...
> >
> > Result result = scanner.next();
> >
> > There's no... result.getKey() - so what method would give me the Key
> value?
> >
> >
> >
> > On Wed, Feb 2, 2011 at 10:20 PM, Stack <[EMAIL PROTECTED]> wrote:
> >
> >> See
> >>
> http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FirstKeyOnlyFilter.html
> >> St.Ack
> >>
> >> On Thu, Feb 3, 2011 at 6:01 AM, Something Something
> >> <[EMAIL PROTECTED]> wrote:
> >> > I want to read only the keys in a table. I tried this...
> >> >
> >> > try {
> >> >
> >> > HTable table = new HTable("myTable");
> >> >
> >> > Scan scan = new Scan();
> >> >
> >> > scan.addFamily(Bytes.toBytes("Info"));
> >> >
> >> > ResultScanner scanner = table.getScanner(scan);
> >> >
> >> > Result result = scanner.next();
> >> >
> >> > while (result != null) {
> >> >
> >> > & so on...
> >> >
> >> > This was performing fairly well until I added another Family that
> >> contains
> >> > lots of key/value pairs. My understanding was that adding another
> family
> >> > wouldn't affect performance of this code because I am explicitly using
> >> > "Info", but it is.
> >> >
> >> > Anyway, in this particular use case, I only care about the "Key" of
> the
> >> row.
> >> > I don't need any values from any of the families. What's the best
> way
> >> to
> >> > do this?
> >> >
> >> > Please let me know. Thanks.
> >> >
> >>
> >
>

RE: Fastest way to read only the keys of a HTable?

Jonathan Gray 2011-02-03, 20:15

If you only need to consider a single column family, use Scan.addFamily() on your scanner. Then there will be no impact of the other column families.

> -----Original Message-----
> From: Something Something [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, February 03, 2011 11:28 AM
> To: [EMAIL PROTECTED]
> Subject: Re: Fastest way to read only the keys of a HTable?
>
> Hmm.. performance hasn't improved at all. Do you see anything wrong with
> the following code:
>
>
> public List<Partner> getPartners() {
> ArrayList<Partner> partners = new ArrayList<Partner>();
>
> try {
> HTable table = new HTable("partner");
> Scan scan = new Scan();
> scan.setFilter(new FirstKeyOnlyFilter());
> ResultScanner scanner = table.getScanner(scan);
> Result result = scanner.next();
> while (result != null) {
> Partner partner = new
> Partner(Bytes.toString(result.getRow()));
> partners.add(partner);
> result = scanner.next();
> }
> } catch (IOException e) {
> throw new RuntimeException(e);
> }
> return partners;
> }
>
> May be I shouldn't use more than one "column family" in a HTable - but the
> BigTable paper recommends that, doesn't it? Please advice and thanks for
> your help.
>
>
>
>
> On Wed, Feb 2, 2011 at 10:55 PM, Stack <[EMAIL PROTECTED]> wrote:
>
> > I don't see a getKey on Result. Use
> >
> >
> http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Result.
> > html#getRow()
> > .
> >
> > Here is how its used in the shell table.rb class:
> >
> > # Count rows in a table
> > def count(interval = 1000, caching_rows = 10)
> > # We can safely set scanner caching with the first key only filter
> > scan = org.apache.hadoop.hbase.client.Scan.new
> > scan.cache_blocks = false
> > scan.caching = caching_rows
> >
> > scan.setFilter(org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter.new)
> >
> > # Run the scanner
> > scanner = @table.getScanner(scan)
> > count = 0
> > iter = scanner.iterator
> >
> > # Iterate results
> > while iter.hasNext
> > row = iter.next
> > count += 1
> > next unless (block_given? && count % interval == 0)
> > # Allow command modules to visualize counting process
> > yield(count, String.from_java_bytes(row.getRow))
> > end
> >
> > # Return the counter
> > return count
> > end
> >
> >
> > St.Ack
> >
> > On Thu, Feb 3, 2011 at 6:47 AM, Something Something
> > <[EMAIL PROTECTED]> wrote:
> > > Thanks. So I will add this...
> > >
> > > scan.setFilter(new FirstKeyOnlyFilter());
> > >
> > > But after I do this...
> > >
> > > Result result = scanner.next();
> > >
> > > There's no... result.getKey() - so what method would give me the
> > > Key
> > value?
> > >
> > >
> > >
> > > On Wed, Feb 2, 2011 at 10:20 PM, Stack <[EMAIL PROTECTED]> wrote:
> > >
> > >> See
> > >>
> > http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FirstKe
> > yOnlyFilter.html
> > >> St.Ack
> > >>
> > >> On Thu, Feb 3, 2011 at 6:01 AM, Something Something
> > >> <[EMAIL PROTECTED]> wrote:
> > >> > I want to read only the keys in a table. I tried this...
> > >> >
> > >> > try {
> > >> >
> > >> > HTable table = new HTable("myTable");
> > >> >
> > >> > Scan scan = new Scan();
> > >> >
> > >> > scan.addFamily(Bytes.toBytes("Info"));
> > >> >
> > >> > ResultScanner scanner = table.getScanner(scan);
> > >> >
> > >> > Result result = scanner.next();
> > >> >
> > >> > while (result != null) {
> > >> >
> > >> > & so on...
> > >> >
> > >> > This was performing fairly well until I added another Family that
> > >> contains
> > >> > lots of key/value pairs. My understanding was that adding
> > >> > another
> > family
> > >> > wouldn't affect performance of this code because I am explicitly
> > >> > using "Info", but it is.
> > >> >
> > >> > Anyway, in this particular use case, I only care about the "Key"

Re: Fastest way to read only the keys of a HTable?

Something Something 2011-02-03, 21:35

After adding the following line:

scan.addFamily(Bytes.toBytes("Info"));

performance improved dramatically (Thank you both!). But now I want it to
perform even faster, if possible -:) To read 43 rows, it's taking 2
seconds. Eventually, the 'partner' table may have over 500 entries. I
guess, I will try by moving the recently added family to a different table.
Do you think that might help?

Thanks again.
On Thu, Feb 3, 2011 at 12:15 PM, Jonathan Gray <[EMAIL PROTECTED]> wrote:

> If you only need to consider a single column family, use Scan.addFamily()
> on your scanner. Then there will be no impact of the other column families.
>
> > -----Original Message-----
> > From: Something Something [mailto:[EMAIL PROTECTED]]
> > Sent: Thursday, February 03, 2011 11:28 AM
> > To: [EMAIL PROTECTED]
> > Subject: Re: Fastest way to read only the keys of a HTable?
> >
> > Hmm.. performance hasn't improved at all. Do you see anything wrong with
> > the following code:
> >
> >
> > public List<Partner> getPartners() {
> > ArrayList<Partner> partners = new ArrayList<Partner>();
> >
> > try {
> > HTable table = new HTable("partner");
> > Scan scan = new Scan();
> > scan.setFilter(new FirstKeyOnlyFilter());
> > ResultScanner scanner = table.getScanner(scan);
> > Result result = scanner.next();
> > while (result != null) {
> > Partner partner = new
> > Partner(Bytes.toString(result.getRow()));
> > partners.add(partner);
> > result = scanner.next();
> > }
> > } catch (IOException e) {
> > throw new RuntimeException(e);
> > }
> > return partners;
> > }
> >
> > May be I shouldn't use more than one "column family" in a HTable - but
> the
> > BigTable paper recommends that, doesn't it? Please advice and thanks for
> > your help.
> >
> >
> >
> >
> > On Wed, Feb 2, 2011 at 10:55 PM, Stack <[EMAIL PROTECTED]> wrote:
> >
> > > I don't see a getKey on Result. Use
> > >
> > >
> > http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Result.
> > > html#getRow()
> > > .
> > >
> > > Here is how its used in the shell table.rb class:
> > >
> > > # Count rows in a table
> > > def count(interval = 1000, caching_rows = 10)
> > > # We can safely set scanner caching with the first key only filter
> > > scan = org.apache.hadoop.hbase.client.Scan.new
> > > scan.cache_blocks = false
> > > scan.caching = caching_rows
> > >
> > > scan.setFilter(org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter.new)
> > >
> > > # Run the scanner
> > > scanner = @table.getScanner(scan)
> > > count = 0
> > > iter = scanner.iterator
> > >
> > > # Iterate results
> > > while iter.hasNext
> > > row = iter.next
> > > count += 1
> > > next unless (block_given? && count % interval == 0)
> > > # Allow command modules to visualize counting process
> > > yield(count, String.from_java_bytes(row.getRow))
> > > end
> > >
> > > # Return the counter
> > > return count
> > > end
> > >
> > >
> > > St.Ack
> > >
> > > On Thu, Feb 3, 2011 at 6:47 AM, Something Something
> > > <[EMAIL PROTECTED]> wrote:
> > > > Thanks. So I will add this...
> > > >
> > > > scan.setFilter(new FirstKeyOnlyFilter());
> > > >
> > > > But after I do this...
> > > >
> > > > Result result = scanner.next();
> > > >
> > > > There's no... result.getKey() - so what method would give me the
> > > > Key
> > > value?
> > > >
> > > >
> > > >
> > > > On Wed, Feb 2, 2011 at 10:20 PM, Stack <[EMAIL PROTECTED]> wrote:
> > > >
> > > >> See
> > > >>
> > > http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/FirstKe
> > > yOnlyFilter.html
> > > >> St.Ack
> > > >>
> > > >> On Thu, Feb 3, 2011 at 6:01 AM, Something Something
> > > >> <[EMAIL PROTECTED]> wrote:
> > > >> > I want to read only the keys in a table. I tried this...
> > > >> >

Re: Fastest way to read only the keys of a HTable?

Jean-Daniel Cryans 2011-02-03, 22:17

On the scan, you can setCaching with the number of rows you want to
pre-fetch per RPC. Setting it to 2 is already 2x better than the
default.

J-D

On Thu, Feb 3, 2011 at 1:35 PM, Something Something
<[EMAIL PROTECTED]> wrote:
> After adding the following line:
>
> scan.addFamily(Bytes.toBytes("Info"));
>
> performance improved dramatically (Thank you both!). But now I want it to
> perform even faster, if possible -:) To read 43 rows, it's taking 2
> seconds. Eventually, the 'partner' table may have over 500 entries. I
> guess, I will try by moving the recently added family to a different table.
> Do you think that might help?
>
> Thanks again.
>
>
> On Thu, Feb 3, 2011 at 12:15 PM, Jonathan Gray <[EMAIL PROTECTED]> wrote:
>
>> If you only need to consider a single column family, use Scan.addFamily()
>> on your scanner. Then there will be no impact of the other column families.
>>
>> > -----Original Message-----
>> > From: Something Something [mailto:[EMAIL PROTECTED]]
>> > Sent: Thursday, February 03, 2011 11:28 AM
>> > To: [EMAIL PROTECTED]
>> > Subject: Re: Fastest way to read only the keys of a HTable?
>> >
>> > Hmm.. performance hasn't improved at all. Do you see anything wrong with
>> > the following code:
>> >
>> >
>> > public List<Partner> getPartners() {
>> > ArrayList<Partner> partners = new ArrayList<Partner>();
>> >
>> > try {
>> > HTable table = new HTable("partner");
>> > Scan scan = new Scan();
>> > scan.setFilter(new FirstKeyOnlyFilter());
>> > ResultScanner scanner = table.getScanner(scan);
>> > Result result = scanner.next();
>> > while (result != null) {
>> > Partner partner = new
>> > Partner(Bytes.toString(result.getRow()));
>> > partners.add(partner);
>> > result = scanner.next();
>> > }
>> > } catch (IOException e) {
>> > throw new RuntimeException(e);
>> > }
>> > return partners;
>> > }
>> >
>> > May be I shouldn't use more than one "column family" in a HTable - but
>> the
>> > BigTable paper recommends that, doesn't it? Please advice and thanks for
>> > your help.
>> >
>> >
>> >
>> >
>> > On Wed, Feb 2, 2011 at 10:55 PM, Stack <[EMAIL PROTECTED]> wrote:
>> >
>> > > I don't see a getKey on Result. Use
>> > >
>> > >
>> > http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Result.
>> > > html#getRow()
>> > > .
>> > >
>> > > Here is how its used in the shell table.rb class:
>> > >
>> > > # Count rows in a table
>> > > def count(interval = 1000, caching_rows = 10)
>> > > # We can safely set scanner caching with the first key only filter
>> > > scan = org.apache.hadoop.hbase.client.Scan.new
>> > > scan.cache_blocks = false
>> > > scan.caching = caching_rows
>> > >
>> > > scan.setFilter(org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter.new)
>> > >
>> > > # Run the scanner
>> > > scanner = @table.getScanner(scan)
>> > > count = 0
>> > > iter = scanner.iterator
>> > >
>> > > # Iterate results
>> > > while iter.hasNext
>> > > row = iter.next
>> > > count += 1
>> > > next unless (block_given? && count % interval == 0)
>> > > # Allow command modules to visualize counting process
>> > > yield(count, String.from_java_bytes(row.getRow))
>> > > end
>> > >
>> > > # Return the counter
>> > > return count
>> > > end
>> > >
>> > >
>> > > St.Ack
>> > >
>> > > On Thu, Feb 3, 2011 at 6:47 AM, Something Something
>> > > <[EMAIL PROTECTED]> wrote:
>> > > > Thanks. So I will add this...
>> > > >
>> > > > scan.setFilter(new FirstKeyOnlyFilter());
>> > > >
>> > > > But after I do this...
>> > > >
>> > > > Result result = scanner.next();
>> > > >
>> > > > There's no... result.getKey() - so what method would give me the
>> > > > Key
>> > > value?
>> > > >
>> > > >
>> > > >
>> > > > On Wed, Feb 2, 2011 at 10:20 PM, Stack <[EMAIL PROTECTED]> wrote:

Re: Fastest way to read only the keys of a HTable?

Something Something 2011-02-03, 23:09

Awesome! It's instantaneous now. Thanks a bunch. Any such tricks for code
that looks like this...

   Get get = new Get(Bytes.toBytes(code));
   Result result = table.get(get);
   NavigableMap<byte[], byte[]> map result.getFamilyMap(Bytes.toBytes("Keys"));
   if (map != null) {
   for (Map.Entry<byte[], byte[]> entry : map.entrySet()) {
   String key = Bytes.toString(entry.getValue());
   Get get1 = new Get(Bytes.toBytes(key));
   Result imp = table2.get(get1);
   // Do something with the result...
   }
   }

Basically, I am reading the first table by a key (code). The "Keys" family
contains keys of some other table, so I get each key from that family and
retrieve row from the other table.

Thanks again.

On Thu, Feb 3, 2011 at 2:17 PM, Jean-Daniel Cryans <[EMAIL PROTECTED]>wrote:

> On the scan, you can setCaching with the number of rows you want to
> pre-fetch per RPC. Setting it to 2 is already 2x better than the
> default.
>
> J-D
>
> On Thu, Feb 3, 2011 at 1:35 PM, Something Something
> <[EMAIL PROTECTED]> wrote:
> > After adding the following line:
> >
> > scan.addFamily(Bytes.toBytes("Info"));
> >
> > performance improved dramatically (Thank you both!). But now I want it
> to
> > perform even faster, if possible -:) To read 43 rows, it's taking 2
> > seconds. Eventually, the 'partner' table may have over 500 entries. I
> > guess, I will try by moving the recently added family to a different
> table.
> > Do you think that might help?
> >
> > Thanks again.
> >
> >
> > On Thu, Feb 3, 2011 at 12:15 PM, Jonathan Gray <[EMAIL PROTECTED]> wrote:
> >
> >> If you only need to consider a single column family, use
> Scan.addFamily()
> >> on your scanner. Then there will be no impact of the other column
> families.
> >>
> >> > -----Original Message-----
> >> > From: Something Something [mailto:[EMAIL PROTECTED]]
> >> > Sent: Thursday, February 03, 2011 11:28 AM
> >> > To: [EMAIL PROTECTED]
> >> > Subject: Re: Fastest way to read only the keys of a HTable?
> >> >
> >> > Hmm.. performance hasn't improved at all. Do you see anything wrong
> with
> >> > the following code:
> >> >
> >> >
> >> > public List<Partner> getPartners() {
> >> > ArrayList<Partner> partners = new ArrayList<Partner>();
> >> >
> >> > try {
> >> > HTable table = new HTable("partner");
> >> > Scan scan = new Scan();
> >> > scan.setFilter(new FirstKeyOnlyFilter());
> >> > ResultScanner scanner = table.getScanner(scan);
> >> > Result result = scanner.next();
> >> > while (result != null) {
> >> > Partner partner = new
> >> > Partner(Bytes.toString(result.getRow()));
> >> > partners.add(partner);
> >> > result = scanner.next();
> >> > }
> >> > } catch (IOException e) {
> >> > throw new RuntimeException(e);
> >> > }
> >> > return partners;
> >> > }
> >> >
> >> > May be I shouldn't use more than one "column family" in a HTable - but
> >> the
> >> > BigTable paper recommends that, doesn't it? Please advice and thanks
> for
> >> > your help.
> >> >
> >> >
> >> >
> >> >
> >> > On Wed, Feb 2, 2011 at 10:55 PM, Stack <[EMAIL PROTECTED]> wrote:
> >> >
> >> > > I don't see a getKey on Result. Use
> >> > >
> >> > >
> >> > http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/client/Result
> .
> >> > > html#getRow()
> >> > > .
> >> > >
> >> > > Here is how its used in the shell table.rb class:
> >> > >
> >> > > # Count rows in a table
> >> > > def count(interval = 1000, caching_rows = 10)
> >> > > # We can safely set scanner caching with the first key only
> filter
> >> > > scan = org.apache.hadoop.hbase.client.Scan.new
> >> > > scan.cache_blocks = false
> >> > > scan.caching = caching_rows
> >> > >
> >> > >
> scan.setFilter(org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter.new)
> >> > >
> >> > > # Run the scanner