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Accumulo, mail # user - Performance of table with large number of column families


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Anthony Fox 2012-11-09, 16:26
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William Slacum 2012-11-09, 16:39
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William Slacum 2012-11-09, 16:41
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Anthony Fox 2012-11-09, 16:45
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William Slacum 2012-11-09, 16:49
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Anthony Fox 2012-11-09, 16:52
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Anthony Fox 2012-11-09, 16:53
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William Slacum 2012-11-09, 17:02
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Anthony Fox 2012-11-09, 17:11
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Re: Performance of table with large number of column families
William Slacum 2012-11-09, 17:15
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 table.split.threshold.  I
>>>> started at 1G and bumped it down to 128M and the cf scan is still ~30
>>>> seconds for both.  I've also used less rows - 00000 to 99999 and still see
>>>> similar performance numbers.  I thought the column family bloom filter
>>>> would help deal with large row space but sparsely populated column space.
>>>>  Is that correct?
>>>>
>>>>
>>>> On Fri, Nov 9, 2012 at 11:49 AM, William Slacum <
>>>> [EMAIL PROTECTED]> wrote:
>>>>
>>>>> I'm more inclined to believe it's because you have to search across
>>>>> 10M different rows to find any given column family, since they're randomly,
>>>>> and possibly uniformly, distributed. How many tablets are you searching
>>>>> across?
>>>>>
>>>>>
>>>>> On Fri, Nov 9, 2012 at 11:45 AM, Anthony Fox <[EMAIL PROTECTED]>wrote:
>>>>>
>>>>>> Yes, there are 10M possible partitions.  I do not have a hash from
>>>>>> value to partition, the data is essentially randomly balanced across all
>>>>>> the tablets.  Unlike the bloom filter and intersecting iterator examples, I
>>>>>> do not have locality groups turned on and I have data in the cq and the
>>>>>> value for both index entries and record entries.  Could this be the issue?
>>>>>>  Each record entry has approximately 30 column qualifiers with data in the
>>>>>> value for each.
>>>>>>
>>>>>>
>>>>>> On Fri, Nov 9, 2012 at 11:41 AM, William Slacum <
>>>>>> [EMAIL PROTECTED]> wrote:
>>>>>>
>>>>>>> I guess assuming you have 10M possible partitions, if you're using a
>>>>>>> relatively uniform hash to generate your IDs, you'll average about 2 per
>>>>>>> partition. Do you have any index for term/value to partition? This will
>>>>>>> help you narrow down your search space to a subset of your partitions.
>>>>>>>
>>>>>>>
>>>>>>> On Fri, Nov 9, 2012 at 11:39 AM, William Slacum <
>>>>>>> [EMAIL PROTECTED]> wrote:
>>>>>>>
>>>>>>>> That shouldn't be a huge issue. How many rows/partitions do you
>>>>>>>> have? How many do you have to scan to find the specific column family/doc
>>>>>>>> id you want?
>>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, Nov 9, 2012 at 11:26 AM, Anthony Fox <[EMAIL PROTECTED]>wrote:
>>>>>>>>
>>>>>>>>> I have a table set up to use the intersecting iterator pattern.  The
>>>>>>>>> table has about 20M records which leads to 20M column families for the
>>>>>>>>> data section - 1 unique column family per record.  The index section of
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Anthony Fox 2012-11-09, 17:18
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William Slacum 2012-11-09, 17:23
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John Vines 2012-11-09, 17:41
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Anthony Fox 2012-11-09, 18:02
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John Vines 2012-11-09, 18:09
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Anthony Fox 2012-11-09, 18:29
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Eric Newton 2012-11-09, 18:32