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 >>>>>>>>>> >>>>>>>>>> >>>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >
