GitHub user cloud-fan opened a pull request:
https://github.com/apache/spark/pull/17541
[SPARK-20229][SQL] add semanticHash to QueryPlan
## What changes were proposed in this pull request?
Like `Expression`, `QueryPlan` should also have a `semanticHash` method,
then we can put plans to a hash map and look it up fast. This PR refactors
`QueryPlan` to follow `Expression` and put all the normalization logic in
`QueryPlan.canonicalized`, so that it's very natural to implement
`semanticHash`.
follow-up: improve `CacheManager` to leverage this `semanticHash` and speed
up plan lookup, instead of iterating all cached plans.
## How was this patch tested?
existing tests. Note that we don't need to test the `semanticHash` method,
once the existing tests prove `sameResult` is correct, we are good.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/cloud-fan/spark plan-semantic
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/17541.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 #17541
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commit 02f4a020fc4e91929782ae293895f7e1c5977d72
Author: Wenchen Fan <[email protected]>
Date: 2017-04-05T17:53:42Z
add semanticHash to QueryPlan
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