Wenchen Fan created SPARK-30614:
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Summary: The native ALTER COLUMN syntax should change one thing at
a time
Key: SPARK-30614
URL: https://issues.apache.org/jira/browse/SPARK-30614
Project: Spark
Issue Type: New Feature
Components: SQL
Affects Versions: 3.0.0
Reporter: Wenchen Fan
Our native ALTER COLUMN syntax is newly added in 3.0 and almost follows the SQL
standard.
{{{
ALTER TABLE table=multipartIdentifier
(ALTER | CHANGE) COLUMN? column=multipartIdentifier
(TYPE dataType)?
(COMMENT comment=STRING)?
colPosition?
}}}
The SQL standard (section 11.12) only allows changing one property at a time.
This is also true on other recent SQL systems like
snowflake(https://docs.snowflake.net/manuals/sql-reference/sql/alter-table-column.html)
and redshift(https://docs.aws.amazon.com/redshift/latest/dg/r_ALTER_TABLE.html)
The snowflake has an extension that it allows changing multiple columns at a
time, like ALTER COLUMN c1 TYPE int, c2 TYPE int. If we want to extend the SQL
standard, I think this syntax is better.
For now, let's be conservative and only allow changing one property at a time.
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