Long answer An EXTERNAL TABLE in hive is a stub for table in Hive metastore. Data is not managed by Hive and it is an HDFS concern.
For that reason if you drop an EXTERNAL table in Hive you just drop references for that table in Hive metastore. Data is not deleted. The conventional indexes don't work in Hive (although I would like to see they work) is that HDFS lacks the capability to co-locate index blocks. The classic index keeps the index blocks contiguous on Disk. However, I assume your external table is used for csv files etc. What you can do is to create a managed (normal) Hive table in ORC format and partition it by ndate or Dtsramp = '2016-10-27' Then you can do periodic INSERT/SELECT from the external table to ORC table. In that case you will utilise Store Index in Hive. HTH Dr Mich Talebzadeh LinkedIn * https://www.linkedin.com/profile/view?id=AAEAAAAWh2gBxianrbJd6zP6AcPCCdOABUrV8Pw <https://www.linkedin.com/profile/view?id=AAEAAAAWh2gBxianrbJd6zP6AcPCCdOABUrV8Pw>* http://talebzadehmich.wordpress.com *Disclaimer:* Use it at your own risk. Any and all responsibility for any loss, damage or destruction of data or any other property which may arise from relying on this email's technical content is explicitly disclaimed. The author will in no case be liable for any monetary damages arising from such loss, damage or destruction. On 27 October 2016 at 12:41, Mich Talebzadeh <mich.talebza...@gmail.com> wrote: > Have you checked running SQL with > > EXPLAIN EXTENDED SELECT ...... > > And post the results. > > In general your compact index will not work > > HTH > > Dr Mich Talebzadeh > > > > LinkedIn * > https://www.linkedin.com/profile/view?id=AAEAAAAWh2gBxianrbJd6zP6AcPCCdOABUrV8Pw > <https://www.linkedin.com/profile/view?id=AAEAAAAWh2gBxianrbJd6zP6AcPCCdOABUrV8Pw>* > > > > http://talebzadehmich.wordpress.com > > > *Disclaimer:* Use it at your own risk. Any and all responsibility for any > loss, damage or destruction of data or any other property which may arise > from relying on this email's technical content is explicitly disclaimed. > The author will in no case be liable for any monetary damages arising from > such loss, damage or destruction. > > > > On 27 October 2016 at 12:34, Hilmi Egemen Ciritoğlu < > hilmi.egemen.cirito...@gmail.com> wrote: > >> Hi guys, >> >> I created table and index on this table. Also after I alter that index >> with rebuild option. But still can't see performance improvements. >> >> Only, I can see performance improvements when I query to index table. >> >> I used following commands : >> >> CREATE EXTERNAL TABLE testindex(wban INT, ndate STRING, time STRING, >> stationType STRING, skyCondition STRING, skyConditionFlag STRING, >> visibility INT, >> visibilityFlag INT, weatherType STRING, weatherTypeFlag STRING, >> dryBulbTempF INT, dryBulbTempFFlag INT, wetBulbTempF INT, >> wetBulbTempFFlag INT, wetBulbTempC DOUBLE, webBulbTempCFlag INT, >> dewPointF INT, dewPointFFlag INT, dewPointC INT, dewPointCFlag INT, >> relativeHumidity INT, relativeHumidityFlag INT, windSpeed DOUBLE, >> windSpeedFlag INT, windDirection STRING, windDirectionFlag INT, >> valueForWindCharacter STRING, valueForWindCharacterFlag INT, >> stationPressure DECIMAL, stationPressureFlag INT, pressureTendency INT, >> pressureTendencyFlag INT, pressureChange STRING, pressureChangeFlag INT, >> seaLevelPressure INT, seaLevelPressureFlag INT, recordType STRING, >> recordTypeFlag INT, hourlyPrecip DECIMAL, hourlyPrecipFlag INT, altimeter >> INT, altimeterFlag INT) >> ROW FORMAT DELIMITED >> FIELDS TERMINATED BY ',' >> LINES TERMINATED BY '\n'; >> >> LOAD DATA LOCAL INPATH '/home/user1/Downloads/dataset' INTO TABLE >> testindex; >> >> CREATE INDEX test ON TABLE testindex (ndate) AS 'COMPACT' WITH DEFERRED >> REBUILD; >> ALTER INDEX test ON testindex REBUILD; >> >> Do you know any reason behind this issue ? >> >> Any help would be highly appreciated... >> >> Thanks. >> > >
