David, It's really just a hint. So the splitters will try to hit whatever is defined, but an extra may be created. For instance, BigDecimalSplitter will create 4 splits for certain ranges with 3 MR tasks specified.
-Abe On Wed, Jun 19, 2013 at 5:03 PM, David Kincaid <[email protected]>wrote: > We don't have that set on our cluster and aren't specifying it in our job. > When I look at the different sqoop jobs I see both 3 for some and 4 for > others on the jobs. > > > On Wed, Jun 19, 2013 at 6:50 PM, Abraham Elmahrek <[email protected]>wrote: > >> David, >> >> Well I think sqoop is looking at "mapred.map.tasks". Do you have that set >> in mapred-site.xml? I thought that defaults to 2. >> >> -Abe >> >> >> On Wed, Jun 19, 2013 at 4:31 PM, Abraham Elmahrek <[email protected]>wrote: >> >>> David, >>> >>> I've created https://issues.apache.org/jira/browse/SQOOP-1093 to track >>> the documentation issue. Thanks for bringing this to the community's >>> attention! >>> >>> -Abe >>> >>> >>> On Wed, Jun 19, 2013 at 4:21 PM, Abraham Elmahrek <[email protected]>wrote: >>> >>>> Hey David, >>>> >>>> With oracle, the BigDecimalSplitter will be used by default for all >>>> number types. >>>> >>>> -Abe >>>> >>>> >>>> On Wed, Jun 19, 2013 at 4:05 PM, David Kincaid >>>> <[email protected]>wrote: >>>> >>>>> Abe, the database is Oracle. >>>>> >>>>> >>>>> On Wed, Jun 19, 2013 at 5:48 PM, Abraham Elmahrek >>>>> <[email protected]>wrote: >>>>> >>>>>> David, >>>>>> >>>>>> What database are you importing from? The description I gave was for >>>>>> datatypes that map to the BigDecimal Splitter. The userguide might be >>>>>> referring to the IntegerSplitter which will add the remainder to the last >>>>>> value. >>>>>> >>>>>> -Abe >>>>>> >>>>>> >>>>>> On Wed, Jun 19, 2013 at 1:23 PM, David Kincaid < >>>>>> [email protected]> wrote: >>>>>> >>>>>>> Thanks. We didn't specify the number of mappers, so it's giving us >>>>>>> 4. I understand your explanation, but it seems to conflict with the >>>>>>> Sqoop >>>>>>> user guide ( >>>>>>> http://sqoop.apache.org/docs/1.4.3/SqoopUserGuide.html#_controlling_parallelism >>>>>>> ): >>>>>>> >>>>>>> "When performing parallel imports, Sqoop needs a criterion by which >>>>>>> it can split the workload. Sqoop uses a *splitting column* to split >>>>>>> the workload. By default, Sqoop will identify the primary key column (if >>>>>>> present) in a table and use it as the splitting column. The low and high >>>>>>> values for the splitting column are retrieved from the database, and the >>>>>>> map tasks operate on evenly-sized components of the total range. For >>>>>>> example, if you had a table with a primary key column of id whose >>>>>>> minimum value was 0 and maximum value was 1000, and Sqoop was directed >>>>>>> to >>>>>>> use 4 tasks, Sqoop would run four processes which each execute SQL >>>>>>> statements of the form SELECT * FROM sometable WHERE id >= lo AND >>>>>>> id < hi, with (lo, hi) set to (0, 250), (250, 500), (500, 750), and >>>>>>> (750, 1001) in the different tasks." >>>>>>> >>>>>>> >>>>>>> On Wed, Jun 19, 2013 at 3:14 PM, Abraham Elmahrek >>>>>>> <[email protected]>wrote: >>>>>>> >>>>>>>> Hey David, >>>>>>>> >>>>>>>> Here's the algorithm: >>>>>>>> Split lengths are defined by (max - min)/(# mappers) and whatever >>>>>>>> is left is tacked on at the end. So in this case, (288272191-2110)/3 >>>>>>>> = 96090027.33... So I'm assuming the .33... is rounded down and split >>>>>>>> lengths will be of length 96090027. Sqoop will then create splits >>>>>>>> with the following points: (min) + (range length)*(n). We can see >>>>>>>> that 2110 + 96090027*0 = 2110, 2110 + 96090027*1 = 96092137, 2110 >>>>>>>> + 96090027*2 = 192182164, and 2110 + 96090027*3 = 288272191 will >>>>>>>> be generated based off of this algorithm. The last point to be added >>>>>>>> will >>>>>>>> be 288272192 because the max value is not part of the generated >>>>>>>> split points. Then sqoop will distributed accordingly based off of >>>>>>>> these >>>>>>>> points as you've pointed out above. >>>>>>>> >>>>>>>> Just to be sure, did you configure sqoop to use 3 mappers? >>>>>>>> >>>>>>>> Hope this helps, >>>>>>>> -Abe >>>>>>>> >>>>>>>> >>>>>>>> On Wed, Jun 19, 2013 at 8:33 AM, David Kincaid < >>>>>>>> [email protected]> wrote: >>>>>>>> >>>>>>>>> We're seeing a strange thing happen with a sqoop import job with >>>>>>>>> the way the key range is getting distributed among the 4 mappers that >>>>>>>>> are >>>>>>>>> running. The minimum key value is 2110 and the maximum value is >>>>>>>>> 288272191. >>>>>>>>> We are getting one mapper that is only getting one record to import. >>>>>>>>> Here >>>>>>>>> is the distribution among the mappers: >>>>>>>>> >>>>>>>>> [2110, 96092137) >>>>>>>>> [96092137, 192182164) >>>>>>>>> [192182164, 288272191) >>>>>>>>> [288272191, 288272192) >>>>>>>>> >>>>>>>>> you can see that the fourth mapper is given a range with only one >>>>>>>>> value in it. Could someone help me understand what is going on? >>>>>>>>> >>>>>>>>> Thanks, >>>>>>>>> >>>>>>>>> Dave >>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >
