[SPARK-50262] Forbid change complex types during altering collation

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0.0
• Fix Version/s: 4.0.0
• Component/s: SQL
• Labels: pull-request-available
• Assignee: Aleksei Shishkin
• Reporter: Aleksei Shishkin
• Created: 6 days ago 13:33
• Updated: 2 days ago 08:32
• Resolved: 2 days ago 08:32

Description

SPARK-48413 has brought ability to change collation on table.
But it seems to be too wide, because people couldn't change the whole StructType/MapType/ArrayType by altering before.
Right now there is found problem with altering collation when table has metadata. Altering will be failed because of a metadata mismatch between user's type (that doesn't have metadata) and existing schema.
So I suggest to shrink the feature to only leaf string types.
People will be able to change any collation still, but they need to use full column path:

ALTER TABLE table ALTER COLUMN full.column.path TYPE STRING COLLATE UNICODE

Issue Links

• links to: GitHub Pull Request #48803