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[GitHub] [spark] tanelk opened a new pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
tanelk opened a new pull request #32075:
URL: https://github.com/apache/spark/pull/32075
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### What changes were proposed in this pull request?
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Changed the cost comparison function of the CBO to use the ratios of row counts and sizes in bytes.
### Why are the changes needed?
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In #30965 we changed to CBO cost comparison function so it would be "symetric": `A.betterThan(B)` now implies, that `!B.betterThan(A)`.
With that we caused a performance regressions in some queries - TPCDS q19 for example.
The original cost comparison function used the ratios `relativeRows = A.rowCount / B.rowCount` and `relativeSize = A.size / B.size`. The changed function compared "absolute" cost values `costA = w*A.rowCount + (1-w)*A.size` and `costB = w*B.rowCount + (1-w)*B.size`.
Given the input from @wzhfy we decided to go back to the relative values, because otherwise one (size) may overwhelm the other (rowCount). But this time we avoid adding up the ratios.
Originally `A.betterThan(B) => w*relativeRows + (1-w)*relativeSize < 1` was used. Besides being "non-symteric", this also can exhibit one overwhelming other.
For `w=0.5` If `A` size (bytes) is at least 2x larger than `B`, then no matter how many times more rows does the `B` plan have, `B` will allways be considered to be better - `0.5*2 + 0.5*0.00000000000001 > 1`.
When working with ratios, then it would be better to multiply them.
The proposed cost comparison function is: `A.betterThan(B) => relativeRows^w * relativeSize^(1-w) < 1`.
### Does this PR introduce _any_ user-facing change?
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Comparison of the changed TPCDS v1.4 query execution times at sf=10:
| absolute | multiplicative | | additive |
-- | -- | -- | -- | -- | --
q12 | 145 | 137 | -5.52% | 141 | -2.76%
q13 | 264 | 271 | 2.65% | 271 | 2.65%
q17 | 4521 | 4243 | -6.15% | 4348 | -3.83%
q18 | 758 | 466 | -38.52% | 480 | -36.68%
q19 | 38503 | 2167 | -94.37% | 2176 | -94.35%
q20 | 119 | 120 | 0.84% | 126 | 5.88%
q24a | 16429 | 16838 | 2.49% | 17103 | 4.10%
q24b | 16592 | 16999 | 2.45% | 17268 | 4.07%
q25 | 3558 | 3556 | -0.06% | 3675 | 3.29%
q33 | 362 | 361 | -0.28% | 380 | 4.97%
q52 | 1020 | 1032 | 1.18% | 1052 | 3.14%
q55 | 927 | 938 | 1.19% | 961 | 3.67%
q72 | 24169 | 13377 | -44.65% | 24306 | 0.57%
q81 | 1285 | 1185 | -7.78% | 1168 | -9.11%
q91 | 324 | 336 | 3.70% | 337 | 4.01%
q98 | 126 | 129 | 2.38% | 131 | 3.97%
All times are in ms, the change is compared to the situation in the master branch (absolute).
The proposed cost function (multiplicative) significantlly improves the performance on q18, q19 and q72. The original cost function (additive) has similar improvements at q18 and q19. All other chagnes are within the error bars and I would ignore them - perhaps q81 has also improved.
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PlanStabilitySuite
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[GitHub] [spark] maropu commented on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
maropu commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-815390819
I've checked the failed tests are not related to this PR, so I'll merge this.
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[GitHub] [spark] maropu closed pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
maropu closed pull request #32075:
URL: https://github.com/apache/spark/pull/32075
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[GitHub] [spark] SparkQA commented on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
SparkQA commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-814767029
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[GitHub] [spark] SparkQA commented on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
SparkQA commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-814770610
Kubernetes integration test status failure
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[GitHub] [spark] SparkQA commented on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
SparkQA commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-814766581
**[Test build #137008 has finished](https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/137008/testReport)** for PR 32075 at commit [`051e091`](https://github.com/apache/spark/commit/051e091f4791ae3935a8ad9a2c3ad618e092c06c).
* This patch **fails Spark unit tests**.
* This patch merges cleanly.
* This patch adds no public classes.
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[GitHub] [spark] maropu commented on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
maropu commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-815391161
Thanks! Merged to branch-3.1.
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AmplabJenkins commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-814788672
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[GitHub] [spark] SparkQA commented on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
SparkQA commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-814637629
**[Test build #137008 has started](https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/137008/testReport)** for PR 32075 at commit [`051e091`](https://github.com/apache/spark/commit/051e091f4791ae3935a8ad9a2c3ad618e092c06c).
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[GitHub] [spark] SparkQA removed a comment on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
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SparkQA removed a comment on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-814637629
**[Test build #137008 has started](https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/137008/testReport)** for PR 32075 at commit [`051e091`](https://github.com/apache/spark/commit/051e091f4791ae3935a8ad9a2c3ad618e092c06c).
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[GitHub] [spark] tanelk commented on pull request #32075: [SPARK-34922][SQL][3.1] Use a relative cost comparison function in the CBO
Posted by GitBox <gi...@apache.org>.
tanelk commented on pull request #32075:
URL: https://github.com/apache/spark/pull/32075#issuecomment-814848447
@maropu
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