feat: drop if exists (#2859)

* feat: drop if exists

Signed-off-by: tison <wander4096@gmail.com>

* sqlness cases

Signed-off-by: tison <wander4096@gmail.com>

---------

Signed-off-by: tison <wander4096@gmail.com>

src/sql/src/parsers/drop_parser.rs

@@ -29,6 +29,7 @@ impl<'a> ParserContext<'a> {
         }
         let _ = self.parser.next_token();
 
+        let if_exists = self.parser.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);
         let raw_table_ident =
             self.parser
                 .parse_object_name()
@@ -45,7 +46,7 @@ impl<'a> ParserContext<'a> {
             }
         );
 
-        Ok(Statement::DropTable(DropTable::new(table_ident)))
+        Ok(Statement::DropTable(DropTable::new(table_ident, if_exists)))
     }
 }
 
@@ -63,7 +64,15 @@ mod tests {
         let mut stmts = result.unwrap();
         assert_eq!(
             stmts.pop().unwrap(),
-            Statement::DropTable(DropTable::new(ObjectName(vec![Ident::new("foo")])))
+            Statement::DropTable(DropTable::new(ObjectName(vec![Ident::new("foo")]), false))
+        );
+
+        let sql = "DROP TABLE IF EXISTS foo";
+        let result = ParserContext::create_with_dialect(sql, &GreptimeDbDialect {});
+        let mut stmts = result.unwrap();
+        assert_eq!(
+            stmts.pop().unwrap(),
+            Statement::DropTable(DropTable::new(ObjectName(vec![Ident::new("foo")]), true))
         );
 
         let sql = "DROP TABLE my_schema.foo";
@@ -71,10 +80,10 @@ mod tests {
         let mut stmts = result.unwrap();
         assert_eq!(
             stmts.pop().unwrap(),
-            Statement::DropTable(DropTable::new(ObjectName(vec![
-                Ident::new("my_schema"),
-                Ident::new("foo")
-            ])))
+            Statement::DropTable(DropTable::new(
+                ObjectName(vec![Ident::new("my_schema"), Ident::new("foo")]),
+                false
+            ))
         );
 
         let sql = "DROP TABLE my_catalog.my_schema.foo";
@@ -82,11 +91,14 @@ mod tests {
         let mut stmts = result.unwrap();
         assert_eq!(
             stmts.pop().unwrap(),
-            Statement::DropTable(DropTable::new(ObjectName(vec![
-                Ident::new("my_catalog"),
-                Ident::new("my_schema"),
-                Ident::new("foo")
-            ])))
+            Statement::DropTable(DropTable::new(
+                ObjectName(vec![
+                    Ident::new("my_catalog"),
+                    Ident::new("my_schema"),
+                    Ident::new("foo")
+                ]),
+                false
+            ))
         )
     }
 }

src/sql/src/statements/drop.rs

@@ -19,15 +19,24 @@ use sqlparser_derive::{Visit, VisitMut};
 #[derive(Debug, Clone, PartialEq, Eq, Visit, VisitMut)]
 pub struct DropTable {
     table_name: ObjectName,
+    /// drop table if exists
+    drop_if_exists: bool,
 }
 
 impl DropTable {
     /// Creates a statement for `DROP TABLE`
-    pub fn new(table_name: ObjectName) -> Self {
-        Self { table_name }
+    pub fn new(table_name: ObjectName, if_exists: bool) -> Self {
+        Self {
+            table_name,
+            drop_if_exists: if_exists,
+        }
     }
 
     pub fn table_name(&self) -> &ObjectName {
         &self.table_name
     }
+
+    pub fn drop_if_exists(&self) -> bool {
+        self.drop_if_exists
+    }
 }