Module nullable 

Nullable column type (Nullable(T)). Nullable column implementation

ClickHouse Documentation: https://clickhouse.com/docs/en/sql-reference/data-types/nullable

Important Nesting Restrictions

ClickHouse does NOT allow wrapping certain types in Nullable:

• ❌ Nullable(Array(...)) - NOT allowed (Error code 43)
• ❌ Nullable(LowCardinality(...)) - NOT allowed

Correct usage:

• ✅ Array(Nullable(...)) - Nullable elements inside array
• ✅ LowCardinality(Nullable(...)) - Nullable values with dictionary encoding

See: https://github.com/ClickHouse/ClickHouse/issues/1062

Structs

ColumnNullable

Column for nullable values

ColumnNullableT

Typed nullable column wrapper (matches C++ ColumnNullableT)