Rupinder, Hive supports a filter pushdown[1] which means that the predicates in the where clause are pushed down to the storage handler level where either they get handled by the storage handler or delegated to hive if they cannot handle them. As of now, the HBaseStorageHandler only supports primitive types. So when you use strings as keys, behind the scenes they get converted to start and stop keys and restrict the hbase scan. This does not happen for structs. Hence you see a full table scan causing bad performance.
[1] https://cwiki.apache.org/Hive/filterpushdowndev.html On Tue, Apr 30, 2013 at 1:04 PM, Sanjay Subramanian < sanjay.subraman...@wizecommerce.com> wrote: > My experience with hive + hbase has been about 8x slower on an average. > So I went ahead with hive only option. > > Sent from my iPhone > > On Apr 30, 2013, at 11:19 PM, "Rupinder Singh" <rsi...@care.com> wrote: > > Hi, > > > > I have an hbase cluster where I have a table with a composite key. I map > this table to a Hive external table using which I insert/select data > into/from this table: > > CREATE EXTERNAL TABLE event(key > struct<name:string,dateCreated:string,uid:string>, {more columns here}) > > ROW FORMAT DELIMITED > > COLLECTION ITEMS TERMINATED BY '~' > > STORED BY 'org.apache.hadoop.hive.hbase.HBaseStorageHandler' > > WITH SERDEPROPERTIES ("hbase.columns.mapping" = ":key, other columns ") > > TBLPROPERTIES ("hbase.table.name" = "event"); > > > > The table has about 10 million rows. When I do a select * using all 3 > components of the key, essentially selecting just 1 row, the response time > is almost 700 sec, which seems pretty bad. > > > > For comparison purpose, I created another table with a simple string key, > and the rest of the columns etc same. The key is a string UUID. Table has > same number of column families and same number of rows. > > CREATE EXTERNAL TABLE test_event(key string, blah blah….. > > TBLPROPERTIES ("hbase.table.name" = "test_event"); > > > > When I select a single row from this table by doing select * where > key=’something’, the response time is 35 sec. > > > > This seems to indicate that in case of composite keys, there is a full > table scan happening. This seems weird. > > > > What am I missing here? Is there something special I need to do to get > good read performance if I am using composite keys ? > > Insert performance in both cases is comparable and is as per expectation. > > > > Any help is appreciated. > > Here is the env spec: > > > > Amazon EMR > > Hbase Cluster- 3 core nodes with 7.5 GB RAM each, 2 CPUs of 2.2 GHz each. > Master 7.5 GB RAM, 2 CPUs of 2.2 GHz each > > Hive Cluster – 3 core nodes 3.75 GB RAM each, 1 CPU of 1.8 GHz. Master > 3.75 GB RAM, 1 CPU of 1.8 GHz > > > > Thanks > > Rupinder > > > This email is intended for the person(s) to whom it is addressed and may > contain information that is PRIVILEGED or CONFIDENTIAL. Any unauthorized > use, distribution, copying, or disclosure by any person other than the > addressee(s) is strictly prohibited. If you have received this email in > error, please notify the sender immediately by return email and delete the > message and any attachments from your system. > > > CONFIDENTIALITY NOTICE > ====================== > This email message and any attachments are for the exclusive use of the > intended recipient(s) and may contain confidential and privileged > information. Any unauthorized review, use, disclosure or distribution is > prohibited. If you are not the intended recipient, please contact the > sender by reply email and destroy all copies of the original message along > with any attachments, from your computer system. If you are the intended > recipient, please be advised that the content of this message is subject to > access, review and disclosure by the sender's Email System Administrator. > -- Swarnim
