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https://issues.apache.org/jira/browse/SPARK-33300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17225625#comment-17225625
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Aoyuan Liao commented on SPARK-33300:
-------------------------------------
[~tobe] Actually, it is not a bug. It did simplify nested casts recursively.
{code:java}
== Optimized Logical Plan ==
Project [string_date#12 AS CAST(CAST(string_date AS STRING) AS STRING)#24]
+- LogicalRDD [name#8, c1#9, c2#10, c5#11L, string_date#12,
string_timestamp#13, timestamp_field#14, bool_field#15], false
{code}
'AS CAST(CAST(string_date AS STRING) AS STRING)#24' is the alias name given no
user-defined alias name. The optimized string_date#12 is correct. If you give a
alias name like "select cast(cast(s as string) as string) as u from test"),
check the below plans:
{code:java}
== Analyzed Logical Plan ==
u: string
Project [cast(cast(s#16 as string) as string) AS u#15]
+- SubqueryAlias spark_catalog.default.test
+- HiveTableRelation [`default`.`test`,
org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, Data Cols: [s#16],
Partition Cols: []]== Optimized Logical Plan ==
Project [s#16 AS u#15]
+- HiveTableRelation [`default`.`test`,
org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, Data Cols: [s#16],
Partition Cols: []]
{code}
> Rule SimplifyCasts will not work for nested columns
> ---------------------------------------------------
>
> Key: SPARK-33300
> URL: https://issues.apache.org/jira/browse/SPARK-33300
> Project: Spark
> Issue Type: Bug
> Components: Optimizer, SQL
> Affects Versions: 3.0.0
> Reporter: chendihao
> Priority: Minor
>
> We use SparkSQL and Catalyst to optimize the Spark job. We have read the
> source code and test the rule of SimplifyCasts which will work for simple SQL
> without nested cast.
> The SQL "select cast(string_date as string) from t1" will be optimized.
> {code:java}
> == Analyzed Logical Plan ==
> string_date: string
> Project [cast(string_date#12 as string) AS string_date#24]
> +- SubqueryAlias t1
> +- LogicalRDD [name#8, c1#9, c2#10, c5#11L, string_date#12,
> string_timestamp#13, timestamp_field#14, bool_field#15], false
> == Optimized Logical Plan ==
> Project [string_date#12]
> +- LogicalRDD [name#8, c1#9, c2#10, c5#11L, string_date#12,
> string_timestamp#13, timestamp_field#14, bool_field#15], false
> {code}
> However, it fail to optimize with the nested cast like this "select
> cast(cast(string_date as string) as string) from t1".
> {code:java}
> == Analyzed Logical Plan ==
> CAST(CAST(string_date AS STRING) AS STRING): string
> Project [cast(cast(string_date#12 as string) as string) AS
> CAST(CAST(string_date AS STRING) AS STRING)#24]
> +- SubqueryAlias t1
> +- LogicalRDD [name#8, c1#9, c2#10, c5#11L, string_date#12,
> string_timestamp#13, timestamp_field#14, bool_field#15], false
> == Optimized Logical Plan ==
> Project [string_date#12 AS CAST(CAST(string_date AS STRING) AS STRING)#24]
> +- LogicalRDD [name#8, c1#9, c2#10, c5#11L, string_date#12,
> string_timestamp#13, timestamp_field#14, bool_field#15], false
> {code}
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