[osipovartem]

Summary

Preserve Snowflake CREATE [OR REPLACE] [TRANSIENT] SCHEMA ... [WITH MANAGED ACCESS] as native AST fields rather than losing modifiers or reparsing SQL in downstream consumers. The public parse_create_schema() entry point is preserved; the private helper carries admitted flags. Existing COMMENT/retention options and CLONE compose with the new grammar.

Dialect capability checks preserve other dialects' behavior. Unsupported TEMP/TEMPORARY/PERSISTENT/SECURE/global and OR ALTER forms still reject. Display emits canonical syntax; serde defaults accept older serialized ASTs.

Reference: Snowflake CREATE SCHEMA syntax.

Compatibility

The three new fields (or_replace, transient, with_managed_access) are a Rust AST source change: exhaustive constructors/patterns must be updated. Serde defaults do not remove that source compatibility requirement. DataFusion and Rustice will be pinned coherently to this revision; unsupported execution modifiers must be rejected, not silently discarded. This parser PR itself enables no schema replacement or managed-access authorization semantics.

Validation

• Full all-feature suite: 1,625 passed, zero failed, seven existing ignored, including doctests.
• All-target/all-feature Clippy with -D warnings passed.
• Formatting and whitespace checks passed.
• Independent read-only review explicitly approved correctness, regression, performance, API and test coverage.
• The initial new negative test incorrectly compared different dialect error messages. The corrected test retains every input and separately requires each dialect to reject it; production code was unchanged by that correction.