[
https://issues.apache.org/jira/browse/SPARK-16355?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Xiao Li updated SPARK-16355:
----------------------------
Description:
When a query containing LIMIT/TABLESAMPLE 0, the statistics could be zero.
Results are correct but it could cause a huge performance regression. For
example,
{noformat}
Seq(("one", 1), ("two", 2), ("three", 3), ("four", 4)).toDF("k", "v")
.createOrReplaceTempView("test")
val df1 = spark.table("test")
val df2 = spark.table("test").limit(0)
val df = df1.join(df2, Seq("k"), "left")
{noformat}
The statistics of both {{df}} and {{df2}} are zero. The statistics values
should never be zero; otherwise `sizeInBytes` of `BinaryNode` will also be zero
(product of children).
was:
When a query containing LIMIT/TABLESAMPLE 0, the statistics could be zero.
Results are correct but it could cause a huge performance regression. For
example,
{noformat}
Seq(("one", 1), ("two", 2), ("three", 3), ("four", 4)).toDF("k", "v")
.createOrReplaceTempView("test")
val df1 = spark.table("test")
val df2 = spark.table("test").limit(0)
val df = df1.join(df2, Seq("k"), "left")
{noformat}
The statistics of both {{df}} and {{df2}} are zero. The statistics values
should never be zero; otherwise `sizeInBytes` of `BinaryNode` will also be zero
(product of children). This PR is to increase it to `1`.
> Incorrect Statistics when Queries Containing LIMIT/TABLESAMPLE 0
> ----------------------------------------------------------------
>
> Key: SPARK-16355
> URL: https://issues.apache.org/jira/browse/SPARK-16355
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.0.0
> Reporter: Xiao Li
>
> When a query containing LIMIT/TABLESAMPLE 0, the statistics could be zero.
> Results are correct but it could cause a huge performance regression. For
> example,
> {noformat}
> Seq(("one", 1), ("two", 2), ("three", 3), ("four", 4)).toDF("k", "v")
> .createOrReplaceTempView("test")
> val df1 = spark.table("test")
> val df2 = spark.table("test").limit(0)
> val df = df1.join(df2, Seq("k"), "left")
> {noformat}
> The statistics of both {{df}} and {{df2}} are zero. The statistics values
> should never be zero; otherwise `sizeInBytes` of `BinaryNode` will also be
> zero (product of children).
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