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https://issues.apache.org/jira/browse/SPARK-31136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17058427#comment-17058427
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Wenchen Fan commented on SPARK-31136:
-------------------------------------
The problem is that, we don't really support the char type, we added it only
for hive tables. In fact, if you look at Spark's official document,
https://spark.apache.org/docs/latest/sql-reference.html#data-types , there is
no char type.
On the other hand, this is a long-standing issue that data source tables simply
treat char type as string type. This behavior is not so bad as char type is
kind of a hidden feature and is intended to only serve for hive tables. But
this does introduce a silent result changing if we create data source tables by
default.
However, I think it's still worth to keep SPARK-30098 to bring Spark perf
benefits to more users. My proposal: fail in the parser if users use char type
to create a data source table. This never works correctly and seems OK to
forbid it.
> Revert SPARK-30098 Use default datasource as provider for CREATE TABLE syntax
> -----------------------------------------------------------------------------
>
> Key: SPARK-31136
> URL: https://issues.apache.org/jira/browse/SPARK-31136
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Dongjoon Hyun
> Priority: Blocker
> Labels: correctness
>
> We need to consider the behavior change of SPARK-30098 .
> This is a placeholder to keep the discussion and the final decision.
> `CREATE TABLE` syntax changes its behavior silently.
> The following is one example of the breaking the existing user data pipelines.
> *Apache Spark 2.4.5*
> {code}
> spark-sql> CREATE TABLE t(a STRING);
> spark-sql> LOAD DATA INPATH '/usr/local/spark/README.md' INTO TABLE t;
> spark-sql> SELECT * FROM t LIMIT 1;
> # Apache Spark
> Time taken: 2.05 seconds, Fetched 1 row(s)
> {code}
> {code}
> spark-sql> CREATE TABLE t(a CHAR(3));
> spark-sql> INSERT INTO TABLE t SELECT 'a ';
> spark-sql> SELECT a, length(a) FROM t;
> a 3
> {code}
> *Apache Spark 3.0.0-preview2*
> {code}
> spark-sql> CREATE TABLE t(a STRING);
> spark-sql> LOAD DATA INPATH '/usr/local/spark/README.md' INTO TABLE t;
> Error in query: LOAD DATA is not supported for datasource tables:
> `default`.`t`;
> {code}
> {code}
> spark-sql> CREATE TABLE t(a CHAR(3));
> spark-sql> INSERT INTO TABLE t SELECT 'a ';
> spark-sql> SELECT a, length(a) FROM t;
> a 2
> {code}
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