[SPARK-18853][SQL] Project (UnaryNode) is way too aggressive in estimating statistics #16274
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lgtm |
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Test build #70113 has finished for PR 16274 at commit
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Test build #70123 has finished for PR 16274 at commit
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hvanhovell
reviewed
Dec 14, 2016
| * The default size of a value of the ArrayType is 100 * the default size of the element type. | ||
| * (We assume that there are 100 elements). | ||
| * The default size of a value of the ArrayType is 1 * the default size of the element type. | ||
| * (We assume that there are 1 elements). |
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Language? (We assume that there is 1 element)
hvanhovell
reviewed
Dec 14, 2016
| * (We assume that there are 1 elements). | ||
| */ | ||
| override def defaultSize: Int = 100 * elementType.defaultSize | ||
| override def defaultSize: Int = 1 * elementType.defaultSize |
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Two nits, otherwise LGTM. |
mallman
reviewed
Dec 14, 2016
| /** | ||
| * The default size of a value of the ArrayType is 100 * the default size of the element type. | ||
| * (We assume that there are 100 elements). | ||
| * The default size of a value of the ArrayType is 1 * the default size of the element type. |
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The default size of a value of the ArrayType is the default size of the element type.
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Outside of some comment grooming, LGTM. |
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LGTM |
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Test build #70141 has finished for PR 16274 at commit
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Contributor
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Merging to master/2.1. Thanks! |
asfgit
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Dec 14, 2016
…ating statistics ## What changes were proposed in this pull request? This patch reduces the default number element estimation for arrays and maps from 100 to 1. The issue with the 100 number is that when nested (e.g. an array of map), 100 * 100 would be used as the default size. This sounds like just an overestimation which doesn't seem that bad (since it is usually better to overestimate than underestimate). However, due to the way we assume the size output for Project (new estimated column size / old estimated column size), this overestimation can become underestimation. It is actually in general in this case safer to assume 1 default element. ## How was this patch tested? This should be covered by existing tests. Author: Reynold Xin <rxin@databricks.com> Closes #16274 from rxin/SPARK-18853. (cherry picked from commit 5d79947) Signed-off-by: Herman van Hovell <hvanhovell@databricks.com>
asfgit
pushed a commit
that referenced
this pull request
Dec 14, 2016
…ating statistics This patch reduces the default number element estimation for arrays and maps from 100 to 1. The issue with the 100 number is that when nested (e.g. an array of map), 100 * 100 would be used as the default size. This sounds like just an overestimation which doesn't seem that bad (since it is usually better to overestimate than underestimate). However, due to the way we assume the size output for Project (new estimated column size / old estimated column size), this overestimation can become underestimation. It is actually in general in this case safer to assume 1 default element. This should be covered by existing tests. Author: Reynold Xin <rxin@databricks.com> Closes #16274 from rxin/SPARK-18853. (cherry picked from commit 5d79947) Signed-off-by: Herman van Hovell <hvanhovell@databricks.com> (cherry picked from commit e8866f9) Signed-off-by: Herman van Hovell <hvanhovell@databricks.com>
robert3005
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to palantir/spark
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Dec 15, 2016
…ating statistics ## What changes were proposed in this pull request? This patch reduces the default number element estimation for arrays and maps from 100 to 1. The issue with the 100 number is that when nested (e.g. an array of map), 100 * 100 would be used as the default size. This sounds like just an overestimation which doesn't seem that bad (since it is usually better to overestimate than underestimate). However, due to the way we assume the size output for Project (new estimated column size / old estimated column size), this overestimation can become underestimation. It is actually in general in this case safer to assume 1 default element. ## How was this patch tested? This should be covered by existing tests. Author: Reynold Xin <rxin@databricks.com> Closes apache#16274 from rxin/SPARK-18853.
uzadude
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to uzadude/spark
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this pull request
Jan 27, 2017
…ating statistics ## What changes were proposed in this pull request? This patch reduces the default number element estimation for arrays and maps from 100 to 1. The issue with the 100 number is that when nested (e.g. an array of map), 100 * 100 would be used as the default size. This sounds like just an overestimation which doesn't seem that bad (since it is usually better to overestimate than underestimate). However, due to the way we assume the size output for Project (new estimated column size / old estimated column size), this overestimation can become underestimation. It is actually in general in this case safer to assume 1 default element. ## How was this patch tested? This should be covered by existing tests. Author: Reynold Xin <rxin@databricks.com> Closes apache#16274 from rxin/SPARK-18853.
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What changes were proposed in this pull request?
This patch reduces the default number element estimation for arrays and maps from 100 to 1. The issue with the 100 number is that when nested (e.g. an array of map), 100 * 100 would be used as the default size. This sounds like just an overestimation which doesn't seem that bad (since it is usually better to overestimate than underestimate). However, due to the way we assume the size output for Project (new estimated column size / old estimated column size), this overestimation can become underestimation. It is actually in general in this case safer to assume 1 default element.
How was this patch tested?
This should be covered by existing tests.