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https://issues.apache.org/jira/browse/HIVE-15339?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rajesh Balamohan updated HIVE-15339:
------------------------------------
Attachment: HIVE-15339.1.patch
Attaching .1 patch.
{noformat}
Without any patch: (compile time 14.2 seconds)
==============
2016-12-02T05:20:34,867 DEBUG [cf8155ce-cf85-41b5-b0a3-4d4a6c75da5e main]
log.PerfLogger: </PERFLOG method=compile start=1480656020666 end=1480656034867
duration=14201 from=org.apache.hadoop.hive.ql.Driver>
With Patch: (compile time 10.6 seconds)
=========
2016-12-02T05:34:53,820 DEBUG [bfe87e40-4260-4f67-9e84-cd89694be1ad main]
log.PerfLogger: </PERFLOG method=compile start=1480656883196 end=1480656893820
duration=10624 from=org.apache.hadoop.hive.ql.Driver>
{noformat}
metastore DB was hosted in postgres and flights table has around 7000
partitions.
\cc [~pxiong], [~ashutoshc], [~jcamachorodriguez]
> Prefetch column stats for fields needed in FilterSelectivityEstimator
> ---------------------------------------------------------------------
>
> Key: HIVE-15339
> URL: https://issues.apache.org/jira/browse/HIVE-15339
> Project: Hive
> Issue Type: Improvement
> Reporter: Rajesh Balamohan
> Priority: Minor
> Attachments: HIVE-15339.1.patch
>
>
> Based on query pattern, {{FilterSelectivityEstimator}} gets column statistics
> from metastore in multiple calls. For instance, in the following query, it
> ends up getting individual column statistics for for flights multiple number
> of times.
> When the table has large number of partitions, getting statistics for columns
> via multiple calls can be very expensive. This would adversely impact the
> overall compilation time. The following query took 14 seconds to compile.
> {noformat}
> SELECT COUNT(`flights`.`flightnum`) AS `cnt_flightnum_ok`,
> YEAR(`flights`.`dateofflight`) AS `yr_flightdate_ok`
> FROM `flights` as `flights`
> JOIN `airlines` ON (`flights`.`uniquecarrier` = `airlines`.`code`)
> JOIN `airports` as `source_airport` ON (`flights`.`origin` =
> `source_airport`.`iata`)
> JOIN `airports` as `dest_airport` ON (`flights`.`dest` =
> `dest_airport`.`iata`)
> GROUP BY YEAR(`flights`.`dateofflight`);
> {noformat}
> It may be helpful to club all columns that need statistics and fetch these
> details in single remote call.
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