Spark 4.2: Fix view rename target namespace

[manuzhang]

Problem

Renaming a qualified view to an unqualified target moves the view into the session's current namespace instead of keeping it in the source view's namespace.

USE catalog.other_ns;
ALTER VIEW source_ns.v RENAME TO v2;   -- v2 lands in other_ns, not source_ns

Root cause

ExtendedDataSourceV2Strategy resolves the rename target with Spark3Util.catalogAndIdentifier before deciding whether the target is actually unqualified. For a single-part target name that helper fills in the current namespace, so the identifier handed to IcebergRenameV2ViewExec already carries the session namespace.

IcebergRenameV2ViewExec does handle an unqualified target correctly — it fills the namespace in from the source view — but that branch is unreachable because the namespace is never empty by the time it runs.

Changes

• Resolve single-part rename targets with an empty namespace, letting IcebergRenameV2ViewExec apply the source view's namespace. This matches Spark's v2 RenameTableExec.
• Resolve multi-part targets relative to the source catalog, keeping the existing cross-catalog move rejection.
• Add a regression test covering a qualified source view renamed to an unqualified target while the session is using another namespace.

Tests

The new test fails on main for all three catalog configurations and passes with the fix. TestViews runs 294 tests with no failures.

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AI Disclosure

• Model: Claude Opus 5
• Platform/Tool: Claude Code
• Human Oversight: partially reviewed
• Prompt Summary: port the Spark 4.1 view rename namespace fix to Spark 4.2, with a regression test.

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