Github user maropu commented on a diff in the pull request:
https://github.com/apache/spark/pull/19773#discussion_r216175940
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala ---
@@ -350,16 +366,11 @@ case class AlterTableChangeColumnCommand(
s"${schema.fieldNames.mkString("[`", "`, `", "`]")}"))
}
- // Add the comment to a column, if comment is empty, return the original
column.
- private def addComment(column: StructField, comment: Option[String]):
StructField = {
- comment.map(column.withComment(_)).getOrElse(column)
- }
-
--- End diff --
ah.... ok. Although the query above doesn't work well, why do users change
column types?
Basically, the query should work? e.g., in postgresql
```
postgres=# create table t(a int, b varchar);
CREATE TABLE
postgres=# insert into t values(1, 'a');
INSERT 0 1
postgres=# alter table t alter column a TYPE varchar;
ALTER TABLE
postgres=# select * from t;
a | b
---+---
1 | a
(1 row)
postgres=# \d t
Table "public.t"
Column | Type | Modifiers
--------+-------------------+-----------
a | character varying |
b | character varying |
```
---
---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org
For additional commands, e-mail: reviews-h...@spark.apache.org
