v.21.11Improvements

Relax nested function for If-combinator check

Relax nested function for If-combinator check (but forbid nested identical combinators). #28828 (Azat Khuzhin).
Relaxed restrictions on nested functions within the If-combinator check, allowing nested different combinators but forbidding nested identical combinators.

Why it matters

This feature improves the flexibility of function nesting in conditional expressions by permitting different nested combinators inside the If-combinator. It prevents only identical combinators from being nested, which enhances query expressiveness while maintaining logical clarity and preventing ambiguous conditions.

How to use it

Users can now write queries with nested conditional combinators inside the If-combinator without any special configuration. The system automatically enforces the rule forbidding nested identical combinators, so users just need to avoid nesting the same combinator type within itself.