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https://issues.apache.org/jira/browse/SPARK-33228?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17220807#comment-17220807
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Apache Spark commented on SPARK-33228:
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User 'viirya' has created a pull request for this issue:
https://github.com/apache/spark/pull/30152
> Don't uncache data when replacing an existing view having the same plan
> -----------------------------------------------------------------------
>
> Key: SPARK-33228
> URL: https://issues.apache.org/jira/browse/SPARK-33228
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.4.8, 3.0.2, 3.1.0
> Reporter: Takeshi Yamamuro
> Assignee: Takeshi Yamamuro
> Priority: Major
> Fix For: 2.4.8, 3.0.2, 3.1.0
>
>
> SPARK-30494's updated the `CreateViewCommand` code to implicitly drop cache
> when replacing an existing view. But, this change drops cache even when
> replacing a view having the same logical plan. A sequence of queries to
> reproduce this as follows;
> {code}
> scala> val df = spark.range(1).selectExpr("id a", "id b")
> scala> df.cache()
> scala> df.explain()
> == Physical Plan ==
> *(1) ColumnarToRow
> +- InMemoryTableScan [a#2L, b#3L]
> +- InMemoryRelation [a#2L, b#3L], StorageLevel(disk, memory, deserialized, 1
> replicas)
> +- *(1) Project [id#0L AS a#2L, id#0L AS b#3L]
> +- *(1) Range (0, 1, step=1, splits=4)
> scala> df.createOrReplaceTempView("t")
> scala> sql("select * from t").explain()
> == Physical Plan ==
> *(1) ColumnarToRow
> +- InMemoryTableScan [a#2L, b#3L]
> +- InMemoryRelation [a#2L, b#3L], StorageLevel(disk, memory, deserialized, 1
> replicas)
> +- *(1) Project [id#0L AS a#2L, id#0L AS b#3L]
> +- *(1) Range (0, 1, step=1, splits=4)
> // If one re-runs the same query `df.createOrReplaceTempView("t")`, the
> cache's swept away
> scala> df.createOrReplaceTempView("t")
> scala> sql("select * from t").explain()
> == Physical Plan ==
> *(1) Project [id#0L AS a#2L, id#0L AS b#3L]
> +- *(1) Range (0, 1, step=1, splits=4)
> {code}
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