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https://issues.apache.org/jira/browse/SPARK-15764?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Reynold Xin updated SPARK-15764:
--------------------------------
Description:
BindReferences contains a n^2 loop which causes performance issues when
operating over large schemas: to determine the ordinal of an input, we perform
a linear scan over the {{input}} array. Because {{input}} can sometimes be a
List, the call to {{input(ordinal).nullable}} can also be {{O(n)}}.
Instead of performing a linear scan, we can convert the input into an array and
build a hash map to map from expression ids to ordinals. The greater up-front
cost of the map construction is offset by the fact that an expression can
contain multiple attribute references, so the cost of the map construction is
amortized across a number of lookups.
was:
BindReferences contains a n^2 loop which causes performance issues when
operating over large schemas: to determine the ordinal of an input, we perform
a linear scan over the {{input}} array. Because {{input}} can sometimes be a
List, the call to {{input(ordinal).nullable}} can also be O(n).
Instead of performing a linear scan, we can convert the input into an array and
build a hash map to map from expression ids to ordinals. The greater up-front
cost of the map construction is offset by the fact that an expression can
contain multiple attribute references, so the cost of the map construction is
amortized across a number of lookups.
> Replace n^2 loop in BindReferences
> ----------------------------------
>
> Key: SPARK-15764
> URL: https://issues.apache.org/jira/browse/SPARK-15764
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Reporter: Josh Rosen
> Assignee: Josh Rosen
> Fix For: 2.0.0
>
>
> BindReferences contains a n^2 loop which causes performance issues when
> operating over large schemas: to determine the ordinal of an input, we
> perform a linear scan over the {{input}} array. Because {{input}} can
> sometimes be a List, the call to {{input(ordinal).nullable}} can also be
> {{O(n)}}.
> Instead of performing a linear scan, we can convert the input into an array
> and build a hash map to map from expression ids to ordinals. The greater
> up-front cost of the map construction is offset by the fact that an
> expression can contain multiple attribute references, so the cost of the map
> construction is amortized across a number of lookups.
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