Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
Accumulo >> mail # user >> Performance of table with large number of column families


Copy link to this message
-
Re: Performance of table with large number of column families
Glad to hear. I typically advice a minimum of 2 shards per tserver. I would
say the maximum is actually based on the tablet size. Others in the country
may disagree/provide better reasoning.

Sent from my phone, pardon the typos and brevity.
On Nov 9, 2012 1:03 PM, "Anthony Fox" <[EMAIL PROTECTED]> wrote:

> Ok, I reingested with 1000 rows and performance for both single record
> scans and index scans is much better.  I'm going to experiment a bit with
> the optimal number of rows.  Thanks for the help, everyone.
>
>
> On Fri, Nov 9, 2012 at 12:41 PM, John Vines <[EMAIL PROTECTED]> wrote:
>
>> The bloom filter checks only occur on a seek, and the way the column
>> family filter works it's it seeks and then does a few scans to see if the
>> appropriate families pop up in the short term. Bloom filter on the column
>> family would be better if you had larger rows to encourage more
>> seeks/minimize the number of rows to do bloom checks.
>>
>> The issue is that you are ultimately checking every single row for a
>> column, which is sparse. It's not that different than doing a full table
>> regex. If you had locality groups set up it would be more performant, until
>> you create locality groups for everything.
>>
>> The intersecting iterators get their performance by being able to operate
>> on large rows to avoid the penalty of checking each row. Minimize the
>> number of partitions you have and it should clear up your issues.
>>
>> John
>>
>> Sent from my phone, pardon the typos and brevity.
>> On Nov 9, 2012 12:24 PM, "William Slacum" <[EMAIL PROTECTED]>
>> wrote:
>>
>>> I'll ask for someone to verify this comment for me (look @ u John W
>>> Vines), but the bloom filter helps when you have a discrete number of
>>> column families that will appear across many rows.
>>>
>>> On Fri, Nov 9, 2012 at 12:18 PM, Anthony Fox <[EMAIL PROTECTED]>wrote:
>>>
>>>> Ah, ok, I was under the impression that this would be really fast since
>>>> I have a column family bloom filter turned on.  Is this not correct?
>>>>
>>>>
>>>> On Fri, Nov 9, 2012 at 12:15 PM, William Slacum <
>>>> [EMAIL PROTECTED]> wrote:
>>>>
>>>>> When I said smaller of tablets, I really mean smaller number of rows
>>>>> :) My apologies.
>>>>>
>>>>> So if you're searching for a random column family in a table, like
>>>>> with a `scan -c <cf>` in the shell, it will start at row 0 and work
>>>>> sequentially up to row 10000000 until it finds the cf.
>>>>>
>>>>>
>>>>> On Fri, Nov 9, 2012 at 12:11 PM, Anthony Fox <[EMAIL PROTECTED]>wrote:
>>>>>
>>>>>> This scan is without the intersecting iterator.  I'm just trying to
>>>>>> pull back a single data record at the moment which corresponds to scanning
>>>>>> for one column family.  I'll try with a smaller number of tablets, but is
>>>>>> the computation effort the same for the scan I am doing?
>>>>>>
>>>>>>
>>>>>> On Fri, Nov 9, 2012 at 12:02 PM, William Slacum <
>>>>>> [EMAIL PROTECTED]> wrote:
>>>>>>
>>>>>>> So that means you have roughly 312.5k rows per tablet, which means
>>>>>>> about 725k column families in any given tablet. The intersecting iterator
>>>>>>> will work at a row per time, so I think at any given moment, it will be
>>>>>>> working through 32 at a time and doing a linear scan through the RFile
>>>>>>> blocks. With RFile indices, that check is usually pretty fast, but you're
>>>>>>> having go through 4 orders of magnitude more data sequentially than you can
>>>>>>> work on. If you can experiment and re-ingest with a smaller number of
>>>>>>> tablets, anywhere between 15 and 45, I think you will see better
>>>>>>> performance.
>>>>>>>
>>>>>>> On Fri, Nov 9, 2012 at 11:53 AM, Anthony Fox <[EMAIL PROTECTED]>wrote:
>>>>>>>
>>>>>>>> Failed to answer the original question - 15 tablet servers, 32
>>>>>>>> tablets/splits.
>>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, Nov 9, 2012 at 11:52 AM, Anthony Fox <[EMAIL PROTECTED]>wrote:
>>>>>>>>
>>>>>>>>> I've tried a number of different settings of