GitHub user JoshRosen opened a pull request:
https://github.com/apache/spark/pull/13505
[SPARK-15764][SQL] Replace N^2 loop in BindReferences
BindReferences contains a n^2 loop which causes performance issues when
operating over large schemas: to determine the ordinal of an attribute
reference, 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.
Perf. benchmarks to follow. /cc @ericl
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/JoshRosen/spark bind-references-improvement
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/13505.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #13505
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commit 6216e944a1aef8dc67a446654c0799c8e9920b4f
Author: Josh Rosen <[email protected]>
Date: 2016-06-04T00:12:16Z
Replace N^2 loop in BindReferences.
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