clickhouse: support ALTER TABLE DROP PARTITION without parentheses

Allow DROP PARTITION expr without parentheses by detecting missing ( and
falling back to parse_expr() for bare partition values.

Author: lustefaniak

src/parser/mod.rs

@@ -6628,12 +6628,18 @@ impl<'a> Parser<'a> {
                     partition: Partition::Part(self.parse_expr()?),
                 }
             } else if self.parse_keyword(Keyword::PARTITION) {
-                self.expect_token(&Token::LParen)?;
-                let partitions = self.parse_comma_separated(Parser::parse_expr)?;
-                self.expect_token(&Token::RParen)?;
-                AlterTableOperation::DropPartitions {
-                    partitions,
-                    if_exists: false,
+                if self.peek_token().token == Token::LParen {
+                    self.expect_token(&Token::LParen)?;
+                    let partitions = self.parse_comma_separated(Parser::parse_expr)?;
+                    self.expect_token(&Token::RParen)?;
+                    AlterTableOperation::DropPartitions {
+                        partitions,
+                        if_exists: false,
+                    }
+                } else {
+                    AlterTableOperation::DropPartition {
+                        partition: Partition::Expr(self.parse_expr()?),
+                    }
                 }
             } else if self.parse_keyword(Keyword::CONSTRAINT) {
                 let if_exists = self.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);

tests/sqlparser_clickhouse.rs

@@ -612,6 +612,55 @@ fn parse_alter_table_drop_partition_and_part() {
         }
         _ => unreachable!(),
     }
+
+    // DROP PARTITION with string literal (no parens)
+    match clickhouse_and_generic()
+        .verified_stmt("ALTER TABLE mt DROP PARTITION '2020-11-21'")
+    {
+        Statement::AlterTable {
+            name, operations, ..
+        } => {
+            assert_eq!("mt", name.to_string());
+            assert_eq!(
+                operations[0],
+                AlterTableOperation::DropPartition {
+                    partition: Partition::Expr(Expr::Value(Value::SingleQuotedString(
+                        "2020-11-21".to_string()
+                    ))),
+                }
+            );
+        }
+        _ => unreachable!(),
+    }
+
+    // DROP PARTITION with numeric literal (no parens)
+    match clickhouse_and_generic().verified_stmt("ALTER TABLE visits DROP PARTITION 201901") {
+        Statement::AlterTable {
+            name, operations, ..
+        } => {
+            assert_eq!("visits", name.to_string());
+            assert_eq!(
+                operations[0],
+                AlterTableOperation::DropPartition {
+                    partition: Partition::Expr(Expr::Value(Value::Number(
+                        "201901".to_string(),
+                        false
+                    ))),
+                }
+            );
+        }
+        _ => unreachable!(),
+    }
+
+    // DROP PARTITION with tuple() function call
+    clickhouse_and_generic().verified_stmt(
+        "ALTER TABLE visits DROP PARTITION tuple(toYYYYMM(toDate('2019-01-25')))",
+    );
+
+    // Multiple statements: DROP PARTITION + DROP PART
+    clickhouse_and_generic().parse_sql_statements(
+        "ALTER TABLE mt DROP PARTITION '2020-11-21'; ALTER TABLE mt DROP PART 'all_4_4_0'",
+    ).unwrap();
 }
 
 #[test]