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https://issues.apache.org/jira/browse/SPARK-28495?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gengliang Wang updated SPARK-28495:
-----------------------------------
Issue Type: Sub-task (was: Improvement)
Parent: SPARK-28589
> Follow ANSI SQL on table insertion
> ----------------------------------
>
> Key: SPARK-28495
> URL: https://issues.apache.org/jira/browse/SPARK-28495
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Gengliang Wang
> Priority: Major
>
> In Spark version 2.4 and earlier, when inserting into a table, Spark will
> cast the data type of input query to the data type of target table by
> coercion. This can be super confusing, e.g. users make a mistake and write
> string values to an int column.
> In data source V2, by default, only upcasting is allowed when inserting data
> into a table. E.g. int -> long and int -> string are allowed, while decimal
> -> double or long -> int are not allowed. The rules of UpCast was originally
> created for Dataset type coercion. They are quite strict and different from
> the behavior of all existing popular DBMS. This is breaking change. It is
> possible that it would hurt some Spark users after 3.0 releases.
> This PR proposes that we can follow the rules of store assignment(section
> 9.2) in ANSI SQL. Two significant differences from Up-Cast:
> 1. Any numeric type can be assigned to another numeric type.
> 2. TimestampType can be assigned DateType
> The new behavior is consistent with PostgreSQL. It is more explainable and
> acceptable than using UpCast .
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