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Posted to issues@calcite.apache.org by "Jiarong Wei (JIRA)" <ji...@apache.org> on 2016/10/11 10:08:20 UTC
[jira] [Created] (CALCITE-1428) Inefficient execution plan of
SELECT and LIMIT for Druid
Jiarong Wei created CALCITE-1428:
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Summary: Inefficient execution plan of SELECT and LIMIT for Druid
Key: CALCITE-1428
URL: https://issues.apache.org/jira/browse/CALCITE-1428
Project: Calcite
Issue Type: Bug
Components: core, druid
Reporter: Jiarong Wei
Assignee: Julian Hyde
For SQLs like:
1. {{SELECT * FROM <table> LIMIT <row_count>}}
2. {{SELECT <all_columns_specified_explicitly> FROM <table> LIMIT <row_count>}}
{{DruidSortRule}} in Druid adapter does take effect and {{LIMIT}} is pushed into {{DruidQuery}}. However the corresponding execution plan isn't chosen as the best one. Thus Calcite will retrieve all data from Druid and purge all unnecessary columns.
These are three SQLs and their corresponding execution plans below for dataset {{wikiticker}} in Druid quickstart:
1. {{SELECT "cityName" FROM "wikiticker" LIMIT 5}}
{code}
rel#27:EnumerableInterpreter.ENUMERABLE.[](input=rel#26:Subset#2.BINDABLE.[])
rel#85:DruidQuery.BINDABLE.[](table=[default, wikiticker],intervals=[1900-01-01T00:00:00.000Z/3000-01-01T00:00:00.000Z],projects=[$3],fetch=5)
{code}
2. {{SELECT * FROM "wikiticker" LIMIT 5}}
{code}
rel#52:EnumerableLimit.ENUMERABLE.[](input=rel#36:Subset#0.ENUMERABLE.[],fetch=5)
rel#79:EnumerableInterpreter.ENUMERABLE.[](input=rel#4:Subset#0.BINDABLE.[])
rel#1:DruidQuery.BINDABLE.[](table=[default, wikiticker],intervals=[1900-01-01T00:00:00.000Z/3000-01-01T00:00:00.000Z])
{code}
3. {{SELECT "__time", "added", "channel", "cityName", "comment", "commentLength", "count", "countryIsoCode", "countryName", "deleted", "delta", "deltaBucket", "diffUrl", "flags", "isAnonymous", "isMinor", "isNew", "isRobot", "isUnpatrolled", "metroCode", "namespace", "page", "regionIsoCode", "regionName", "user", "user_unique" FROM "wikiticker" LIMIT 5}}
{code}
rel#42:EnumerableLimit.ENUMERABLE.[](input=rel#41:Subset#1.ENUMERABLE.[],fetch=5)
rel#113:EnumerableInterpreter.ENUMERABLE.[](input=rel#34:Subset#1.BINDABLE.[])
rel#52:BindableProject.BINDABLE.[](input=rel#4:Subset#0.BINDABLE.[],__time=$0,added=$1,channel=$2,cityName=$3,comment=$4,commentLength=$5,count=$6,countryIsoCode=$7,countryName=$8,deleted=$9,delta=$10,deltaBucket=$11,diffUrl=$12,flags=$13,isAnonymous=$14,isMinor=$15,isNew=$16,isRobot=$17,isUnpatrolled=$18,metroCode=$19,namespace=$20,page=$21,regionIsoCode=$22,regionName=$23,user=USER,user_unique=$25)
rel#1:DruidQuery.BINDABLE.[](table=[default, wikiticker],intervals=[1900-01-01T00:00:00.000Z/3000-01-01T00:00:00.000Z])
{code}
Notice that 2 and 3 should have {{LIMIT}} pushed to {{DruidQuery}} like 1 (and should not have {{EnumerableLimit}})
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