[SPARK-27539][SQL] Fix inaccurate aggregate outputRows estimation with column containing null values #24436
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ok to test |
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Test build #104807 has finished for PR 24436 at commit
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srowen
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Apr 22, 2019
dongjoon-hyun
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dongjoon-hyun
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dongjoon-hyun
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Apr 23, 2019
…h column containing null values ## What changes were proposed in this pull request? This PR is follow up of #24286. As gatorsmile pointed out that column with null value is inaccurate as well. ``` > select key from test; 2 NULL 1 spark-sql> desc extended test key; col_name key data_type int comment NULL min 1 max 2 num_nulls 1 distinct_count 2 ``` The distinct count should be distinct_count + 1 when column contains null value. ## How was this patch tested? Existing tests & new UT added. Closes #24436 from pengbo/aggregation_estimation. Authored-by: pengbo <bo.peng1019@gmail.com> Signed-off-by: Dongjoon Hyun <dhyun@apple.com> (cherry picked from commit d9b2ce0) Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
HyukjinKwon
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May 23, 2019
| val distinctValue: BigInt = if (distinctCount == 0 && columnStat.nullCount.get > 0) { | ||
| 1 | ||
| val distinctValue: BigInt = if (columnStat.nullCount.get > 0) { | ||
| distinctCount + 1 |
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Hm, actually, do we need to count null as distinct value? It's not counted as a distinct value in SQL (F.countDistinct or count(DISTINCT col)) and Pandas (unique() by default) at least.
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Looking into the current impl, seems we ignore null as distinct values:
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Reverting this. I don't think this is a correct fix. |
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I added a comment on the original PR. The reverting looks wrong to me. |
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Jul 23, 2019
…h column containing null values ## What changes were proposed in this pull request? This PR is follow up of apache#24286. As gatorsmile pointed out that column with null value is inaccurate as well. ``` > select key from test; 2 NULL 1 spark-sql> desc extended test key; col_name key data_type int comment NULL min 1 max 2 num_nulls 1 distinct_count 2 ``` The distinct count should be distinct_count + 1 when column contains null value. ## How was this patch tested? Existing tests & new UT added. Closes apache#24436 from pengbo/aggregation_estimation. Authored-by: pengbo <bo.peng1019@gmail.com> Signed-off-by: Dongjoon Hyun <dhyun@apple.com> (cherry picked from commit d9b2ce0) Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
kai-chi
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Jul 25, 2019
…h column containing null values ## What changes were proposed in this pull request? This PR is follow up of apache#24286. As gatorsmile pointed out that column with null value is inaccurate as well. ``` > select key from test; 2 NULL 1 spark-sql> desc extended test key; col_name key data_type int comment NULL min 1 max 2 num_nulls 1 distinct_count 2 ``` The distinct count should be distinct_count + 1 when column contains null value. ## How was this patch tested? Existing tests & new UT added. Closes apache#24436 from pengbo/aggregation_estimation. Authored-by: pengbo <bo.peng1019@gmail.com> Signed-off-by: Dongjoon Hyun <dhyun@apple.com> (cherry picked from commit d9b2ce0) Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
kai-chi
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Aug 1, 2019
…h column containing null values ## What changes were proposed in this pull request? This PR is follow up of apache#24286. As gatorsmile pointed out that column with null value is inaccurate as well. ``` > select key from test; 2 NULL 1 spark-sql> desc extended test key; col_name key data_type int comment NULL min 1 max 2 num_nulls 1 distinct_count 2 ``` The distinct count should be distinct_count + 1 when column contains null value. ## How was this patch tested? Existing tests & new UT added. Closes apache#24436 from pengbo/aggregation_estimation. Authored-by: pengbo <bo.peng1019@gmail.com> Signed-off-by: Dongjoon Hyun <dhyun@apple.com> (cherry picked from commit d9b2ce0) Signed-off-by: Dongjoon Hyun <dhyun@apple.com>
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What changes were proposed in this pull request?
This PR is follow up of #24286. As @gatorsmile pointed out that column with null value is inaccurate as well.
The distinct count should be distinct_count + 1 when column contains null value.
How was this patch tested?
Existing tests & new UT added.