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 >>>>>>>>> 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 >>>>>>>>>>>>>> the table is not quite as large as the data section. The rowkey >>>>>>>>>>>>>> is a >>>>>>>>>>>>>> random padded integer partition between 0000000 and 9999999. I >>>>>>>>>>>>>> turned >>>>>>>>>>>>>> bloom filters on and used the ColumnFamilyFunctor to get >>>>>>>>>>>>>> performant >>>>>>>>>>>>>> column family scans without specifying a range like in the bloom >>>>>>>>>>>>>> filter >>>>>>>>>>>>>> examples in the README. However, my column family scans >>>>>>>>>>>>>> (without any >>>>>>>>>>>>>> custom iterator) are still fairly slow - ~30 seconds for a >>>>>>>>>>>>>> column family >>>>>>>>>>>>>> batch scan of one record. I've also tried RowFunctor but I see >>>>>>>>>>>>>> similar >>>>>>>>>>>>>> performance. Can anyone shed any light on the performance >>>>>>>>>>>>>> metrics I'm >>>>>>>>>>>>>> seeing? >>>>>>>>>>>>>> >>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>> Anthony >>>>>>>>>>>>>> >>>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >
