refactor: changes CreateTableRequest::schema to RawSchema (#1018)

* refactor: changes CreateTableRequest::schema to RawSchema

* refactor(grpc-expr): create_table_schema returns RawSchema

src/datatypes/src/schema/raw.rs

@@ -22,15 +22,38 @@ use crate::schema::{ColumnSchema, Schema, SchemaBuilder};
 /// This struct only contains necessary data to recover the Schema.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct RawSchema {
+    /// Schema of columns.
     pub column_schemas: Vec<ColumnSchema>,
+    /// Index of the timestamp column.
     pub timestamp_index: Option<usize>,
+    /// Schema version.
     pub version: u32,
 }
 
+impl RawSchema {
+    /// Creates a new [RawSchema] from specific `column_schemas`.
+    ///
+    /// Sets [RawSchema::timestamp_index] to the first index of the timestamp
+    /// column. It doesn't check whether time index column is duplicate.
+    pub fn new(column_schemas: Vec<ColumnSchema>) -> RawSchema {
+        let timestamp_index = column_schemas
+            .iter()
+            .position(|column_schema| column_schema.is_time_index());
+
+        RawSchema {
+            column_schemas,
+            timestamp_index,
+            version: 0,
+        }
+    }
+}
+
 impl TryFrom<RawSchema> for Schema {
     type Error = Error;
 
     fn try_from(raw: RawSchema) -> Result<Schema> {
+        // While building Schema, we don't trust the fields, such as timestamp_index,
+        // in RawSchema. We use SchemaBuilder to perform the validation.
         SchemaBuilder::try_from(raw.column_schemas)?
             .version(raw.version)
             .build()
@@ -74,4 +97,33 @@ mod tests {
 
         assert_eq!(schema, schema_new);
     }
+
+    #[test]
+    fn test_new_raw_schema_with_time_index() {
+        let column_schemas = vec![
+            ColumnSchema::new("col1", ConcreteDataType::int32_datatype(), true),
+            ColumnSchema::new(
+                "ts",
+                ConcreteDataType::timestamp_millisecond_datatype(),
+                false,
+            )
+            .with_time_index(true),
+        ];
+        let schema = RawSchema::new(column_schemas);
+        assert_eq!(1, schema.timestamp_index.unwrap());
+    }
+
+    #[test]
+    fn test_new_raw_schema_without_time_index() {
+        let column_schemas = vec![
+            ColumnSchema::new("col1", ConcreteDataType::int32_datatype(), true),
+            ColumnSchema::new(
+                "ts",
+                ConcreteDataType::timestamp_millisecond_datatype(),
+                false,
+            ),
+        ];
+        let schema = RawSchema::new(column_schemas);
+        assert!(schema.timestamp_index.is_none());
+    }
 }