fix: changing column data type can't process type alias (#3972)

src/sql/src/parsers/alter_parser.rs

@@ -308,6 +308,71 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_parse_alter_change_column_alias_type() {
+        let sql_1 = "ALTER TABLE my_metric_1 MODIFY COLUMN a MediumText";
+        let mut result_1 = ParserContext::create_with_dialect(
+            sql_1,
+            &GreptimeDbDialect {},
+            ParseOptions::default(),
+        )
+        .unwrap();
+
+        match result_1.remove(0) {
+            Statement::Alter(alter_table) => {
+                assert_eq!("my_metric_1", alter_table.table_name().0[0].value);
+
+                let alter_operation = alter_table.alter_operation();
+                assert_matches!(
+                    alter_operation,
+                    AlterTableOperation::ChangeColumnType { .. }
+                );
+                match alter_operation {
+                    AlterTableOperation::ChangeColumnType {
+                        column_name,
+                        target_type,
+                    } => {
+                        assert_eq!("a", column_name.value);
+                        assert_eq!(DataType::Text, *target_type);
+                    }
+                    _ => unreachable!(),
+                }
+            }
+            _ => unreachable!(),
+        }
+
+        let sql_2 = "ALTER TABLE my_metric_1 MODIFY COLUMN a TIMESTAMP_US";
+        let mut result_2 = ParserContext::create_with_dialect(
+            sql_2,
+            &GreptimeDbDialect {},
+            ParseOptions::default(),
+        )
+        .unwrap();
+
+        match result_2.remove(0) {
+            Statement::Alter(alter_table) => {
+                assert_eq!("my_metric_1", alter_table.table_name().0[0].value);
+
+                let alter_operation = alter_table.alter_operation();
+                assert_matches!(
+                    alter_operation,
+                    AlterTableOperation::ChangeColumnType { .. }
+                );
+                match alter_operation {
+                    AlterTableOperation::ChangeColumnType {
+                        column_name,
+                        target_type,
+                    } => {
+                        assert_eq!("a", column_name.value);
+                        assert!(matches!(target_type, DataType::Timestamp(Some(6), _)));
+                    }
+                    _ => unreachable!(),
+                }
+            }
+            _ => unreachable!(),
+        }
+    }
+
     #[test]
     fn test_parse_alter_rename_table() {
         let sql = "ALTER TABLE test_table table_t";

src/sql/src/statements/alter.rs

@@ -39,6 +39,10 @@ impl AlterTable {
     pub fn alter_operation(&self) -> &AlterTableOperation {
         &self.alter_operation
     }
+
+    pub fn alter_operation_mut(&mut self) -> &mut AlterTableOperation {
+        &mut self.alter_operation
+    }
 }
 
 impl Display for AlterTable {

src/sql/src/statements/transform/type_alias.rs

@@ -20,6 +20,7 @@ use sqlparser::ast::{
 };
 
 use crate::error::Result;
+use crate::statements::alter::AlterTableOperation;
 use crate::statements::create::{CreateExternalTable, CreateTable};
 use crate::statements::statement::Statement;
 use crate::statements::transform::TransformRule;
@@ -51,6 +52,13 @@ impl TransformRule for TypeAliasTransformRule {
                     .iter_mut()
                     .for_each(|ColumnDef { data_type, .. }| replace_type_alias(data_type));
             }
+            Statement::Alter(alter_table) => {
+                if let AlterTableOperation::ChangeColumnType { target_type, .. } =
+                    alter_table.alter_operation_mut()
+                {
+                    replace_type_alias(target_type)
+                }
+            }
             _ => {}
         }