fix(query): fix variant value can not cast to not null type (#17434)

* fix(query): fix variant value can not cast to not null type

* add tests

* fix

Author: b41sh

src/query/expression/src/evaluator.rs

@@ -377,6 +377,47 @@ impl<'a> Evaluator<'a> {
                     .set_span(span))
                 }
             }
+            (
+                DataType::Nullable(box DataType::Variant) | DataType::Variant,
+                DataType::Boolean
+                | DataType::Number(_)
+                | DataType::String
+                | DataType::Date
+                | DataType::Timestamp,
+            ) => {
+                // allow cast variant to not null types.
+                let cast_fn = format!("to_{}", dest_type.to_string().to_lowercase());
+                if let Some(new_value) = self.run_simple_cast(
+                    span,
+                    src_type,
+                    &dest_type.wrap_nullable(),
+                    value.clone(),
+                    &cast_fn,
+                    validity.clone(),
+                    options,
+                )? {
+                    // remove wrapped null values.
+                    let new_value = match new_value {
+                        Value::Scalar(scalar) => {
+                            if scalar == Scalar::Null {
+                                Value::Scalar(Scalar::default_value(dest_type))
+                            } else {
+                                Value::Scalar(scalar)
+                            }
+                        }
+                        Value::Column(column) => {
+                            let nullable_column = column.as_nullable().unwrap();
+                            Value::Column(nullable_column.column.clone())
+                        }
+                    };
+                    Ok(new_value)
+                } else {
+                    Err(ErrorCode::BadArguments(format!(
+                        "unable to cast type `{src_type}` to type `{dest_type}`"
+                    ))
+                    .set_span(span))
+                }
+            }
             (DataType::Nullable(inner_src_ty), DataType::Nullable(inner_dest_ty)) => match value {
                 Value::Scalar(Scalar::Null) => Ok(Value::Scalar(Scalar::Null)),
                 Value::Scalar(_) => {

tests/sqllogictests/suites/base/03_common/03_0014_insert_into_select.test

@@ -124,5 +124,23 @@ DROP TABLE aggregate_table
 statement ok
 DROP TABLE test_insert
 
+statement ok
+CREATE OR REPLACE TABLE t4(data variant);
+
+statement ok
+INSERT INTO t4 values('{"user_id":1}'),('{"user_id":2}')
+
+statement ok
+CREATE OR REPLACE TABLE t5(data variant, user_id uint8 not null);
+
+statement ok
+INSERT INTO t5 SELECT data, data:user_id AS user_id FROM t4;
+
+query TI
+SELECT * FROM t5;
+----
+{"user_id":1} 1
+{"user_id":2} 2
+
 statement ok
 DROP DATABASE db1