For #1, if you want to count distinct values for F1, you can write a coprocessor which aggregates the count on region server and returns the result to client which does the final aggregation.
Take a look at hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/AggregateImplementation.java and related classes for example. On Mon, Aug 17, 2015 at 10:08 PM, Shushant Arora <shushantaror...@gmail.com> wrote: > Thanks ! > few more doubts : > > 1.Say if requirement is to count distinct value of F1- > > If field is part of key- is hbase can't just scan key and skip value > deserialsation and return result to client which will calculate distinct > and in second approcah Hbase will desrialise the value of return column > containing F1 to cleint which will calculate the distinct. > > 2.For bulk load when LoadIncrementalHFiles runs and regionserver moves the > hfiles from hdfs to region directory - does regionserver localise the hfile > by downloading it to local and then uploading again in region directory? Or > it just moves to to region directory and wait for next compaction to get it > localise as in regionserver failure case? > > > > > On Mon, Aug 17, 2015 at 11:00 PM, Ted Yu <yuzhih...@gmail.com> wrote: > > > For both scenarios you mentioned, field is not leading part of row key. > > You would need to specify timerange or start row / stop row to narrow the > > key range being scanned. > > > > I am leaning toward using second approach. > > > > Cheers > > > > On Mon, Aug 17, 2015 at 9:41 AM, Shushant Arora < > shushantaror...@gmail.com > > > > > wrote: > > > > > ~8-10 fields of size (5 of 20 bytes each )and 3 fields of size 200 > bytes > > > each. > > > > > > On Mon, Aug 17, 2015 at 9:55 PM, Ted Yu <yuzhih...@gmail.com> wrote: > > > > > > > How many fields such as F1 are you considering for embedding in row > > key ? > > > > > > > > Suggested reading: > > > > http://hbase.apache.org/book.html#rowkey.design > > > > http://hbase.apache.org/book.html#client.filter.kvm (see > > > > ColumnPrefixFilter) > > > > > > > > Cheers > > > > > > > > On Mon, Aug 17, 2015 at 8:13 AM, Shushant Arora < > > > shushantaror...@gmail.com > > > > > > > > > wrote: > > > > > > > > > 1.so size limit is per cell's identifier + value ? > > > > > > > > > > What is more optimise - to have field in key or in column family's > > > > column ? > > > > > If pattern is like every row has that field. > > > > > > > > > > Say I have a field F1 in all rows so > > > > > Situtatio -1 > > > > > key1#F1(as composite key) - and rest fields in column > > > > > > > > > > Situation-2 > > > > > key1 as key and F1 part of column family. > > > > > > > > > > > > > > > This is the main reason I asked the key size limit. > > > > > If I asked for no of rows where F1 is = 'someval' will it be faster > > in > > > > > situation-1 than in situation-2. Since in 1 it can return the > result > > > just > > > > > by traversing keys no need to read columns? > > > > > > > > > > > > > > > On Mon, Aug 17, 2015 at 8:27 PM, Ted Yu <yuzhih...@gmail.com> > wrote: > > > > > > > > > > > For #1, it is the limit on a single keyvalue, not row, not key. > > > > > > > > > > > > For #2, please see the following: > > > > > > > > > > > > http://hbase.apache.org/book.html#store.memstore > > > > > > > > > > > > http://hbase.apache.org/book.html#regionserver_splitting_implementation > > > > > > > > > > > > Cheers > > > > > > > > > > > > On Mon, Aug 17, 2015 at 7:36 AM, Shushant Arora < > > > > > shushantaror...@gmail.com > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > 1.Is hbase.client.keyvalue.maxsize is max size of row or key > > only > > > ? > > > > Is > > > > > > > there any limit on key size only ? > > > > > > > 2.Access pattern is mostly on key based only- Is memstores and > > > > regions > > > > > > on a > > > > > > > regionserver are per table basis? Is it if I have multiple > tables > > > it > > > > > will > > > > > > > have multiple memstores instead of few if it would have been > one > > > > large > > > > > > > table ? > > > > > > > > > > > > > > > > > > > > > On Mon, Aug 17, 2015 at 7:29 PM, Ted Yu <yuzhih...@gmail.com> > > > wrote: > > > > > > > > > > > > > > > For #1, take a look at the following in hbase-default.xml : > > > > > > > > > > > > > > > > <name>hbase.client.keyvalue.maxsize</name> > > > > > > > > <value>10485760</value> > > > > > > > > > > > > > > > > For #2, it would be easier to answer if you can outline > access > > > > > patterns > > > > > > > in > > > > > > > > your app. > > > > > > > > > > > > > > > > For #3, adjustment according to current region boundaries is > > done > > > > > > client > > > > > > > > side. Take a look at the javadoc for LoadQueueItem > > > > > > > > in LoadIncrementalHFiles.java > > > > > > > > > > > > > > > > Cheers > > > > > > > > > > > > > > > > On Mon, Aug 17, 2015 at 6:45 AM, Shushant Arora < > > > > > > > shushantaror...@gmail.com > > > > > > > > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > 1.Is there any max limit on key size of hbase table. > > > > > > > > > 2.Is multiple small tables vs one large table which one is > > > > > preferred. > > > > > > > > > 3.for bulk load -when LoadIncremantalHfile is run it again > > > > > > > recalculates > > > > > > > > > the region splits based on region boundary - is this > division > > > > > happens > > > > > > > on > > > > > > > > > client side or server side again at region server or hbase > > > master > > > > > and > > > > > > > > then > > > > > > > > > it assigns the splits which cross target region boundary to > > > > desired > > > > > > > > > regionserver. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
