There are a number of other things you can do with Hive to improve your simple
query.
First is best to upgrade to Hive 1.2.1 or above which will require minimal
effort just ensure that you upgrade your metastore as well.
Second your first column is unique (?) as it is ID so in all probability it is
a monotonically increasing number. You can therefore deploy bucketing to spread
your col1 uniformily as its selectivity is 1.
I just wrote a simple shell routine to create 100K rows in an ORC table.
Divided into 256 buckets. I am running Hive on Spark engine
CREATE TABLE txtest (
ID string
, DESCRIPTION string
)
CLUSTERED BY (ID) INTO 256 BUCKETS
STORED AS ORC
TBLPROPERTIES (
"orc.create.index"="true",
"orc.compress"="SNAPPY",
"orc.stripe.size"="16777216",
"orc.row.index.stride"="10000" )
;
INFO : Loading data to table test.txtest from
hdfs://rhes564:9000/user/hive/warehouse/test.db/txtest/.hive-staging_hive_2016-01-29_16-10-04_765_4205127232246216560-13/-ext-10000
INFO : Table test.txtest stats: [numFiles=256, numRows=100000,
totalSize=5653369, rawDataSize=22200000]
OK let us just do a simple point query as you did
0: jdbc:hive2://rhes564:10010/default> use test;
No rows affected (0.02 seconds)
0: jdbc:hive2://rhes564:10010/default> select * from txtest where id = '1234';
+------------+-----------------------------------------------------+--+
| txtest.id | txtest.description |
+------------+-----------------------------------------------------+--+
| 1234 | R_MaH9oKm_OfLbe8LumdSXzBvDFJFrUIkvUoRm_iDPdeegPEWf |
+------------+-----------------------------------------------------+--+
1 row selected (0.887 seconds)
HTH
Dr Mich Talebzadeh
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From: Frank Luo [mailto:[email protected]]
Sent: 29 January 2016 00:47
To: [email protected]
Subject: bloom filter used in 0.14?
All,
I have a huge table that I periodically want to do select on some particular
value. For example, supposing I have a table for the entire world population.
Then I know the id of “1234” is criminal, hence I want to pull out his
information from the table.
Without any optimization, I have to use thousands of mappers to find just one
id. So not ideal. I tried to enable bloom-filter on the column that I want to
search on. But a simple query shows that the amount of data read is the same as
that without a bloom-filter. So I am questioning whether it is enabled on the
version I am on, which is 0.14. Does anyone know? If bloom-filter is not the
way to go, does anyone have suggestions?
Here is the hql:
create table test
(
col1 STRING,
col2 STRING
) STORED AS ORC
tblproperties ("orc.bloom.filter.columns"="col1");
select * from test where col1 = ‘1234’;
Thx
Frank
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