From 559b7e36d9bafbc6da9e3972136ccfae5c22aeb8 Mon Sep 17 00:00:00 2001
From: vimko <1399950+vimko@users.noreply.github.com>
Date: Wed, 11 Jun 2025 00:26:07 +0800
Subject: [PATCH] Add support for `ALTER TABLE DROP INDEX` (#1865)

---
 src/ast/ddl.rs           |  7 +++++++
 src/ast/spans.rs         |  1 +
 src/parser/mod.rs        |  3 +++
 tests/sqlparser_mysql.rs | 10 ++++++++++
 4 files changed, 21 insertions(+)

diff --git a/src/ast/ddl.rs b/src/ast/ddl.rs
index b0a3708c..059c6196 100644
--- a/src/ast/ddl.rs
+++ b/src/ast/ddl.rs
@@ -187,6 +187,12 @@ pub enum AlterTableOperation {
     DropForeignKey {
         name: Ident,
     },
+    /// `DROP INDEX <index_name>`
+    ///
+    /// [MySQL]: https://dev.mysql.com/doc/refman/8.4/en/alter-table.html
+    DropIndex {
+        name: Ident,
+    },
     /// `ENABLE ALWAYS RULE rewrite_rule_name`
     ///
     /// Note: this is a PostgreSQL-specific operation.
@@ -606,6 +612,7 @@ impl fmt::Display for AlterTableOperation {
             }
             AlterTableOperation::DropPrimaryKey => write!(f, "DROP PRIMARY KEY"),
             AlterTableOperation::DropForeignKey { name } => write!(f, "DROP FOREIGN KEY {name}"),
+            AlterTableOperation::DropIndex { name } => write!(f, "DROP INDEX {name}"),
             AlterTableOperation::DropColumn {
                 has_column_keyword,
                 column_name,
diff --git a/src/ast/spans.rs b/src/ast/spans.rs
index 39d30df9..14664b4c 100644
--- a/src/ast/spans.rs
+++ b/src/ast/spans.rs
@@ -1115,6 +1115,7 @@ impl Spanned for AlterTableOperation {
                 .union_opt(&with_name.as_ref().map(|n| n.span)),
             AlterTableOperation::DropPrimaryKey => Span::empty(),
             AlterTableOperation::DropForeignKey { name } => name.span,
+            AlterTableOperation::DropIndex { name } => name.span,
             AlterTableOperation::EnableAlwaysRule { name } => name.span,
             AlterTableOperation::EnableAlwaysTrigger { name } => name.span,
             AlterTableOperation::EnableReplicaRule { name } => name.span,
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index b582e793..6831d52e 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -8636,6 +8636,9 @@ impl<'a> Parser<'a> {
             } else if self.parse_keywords(&[Keyword::FOREIGN, Keyword::KEY]) {
                 let name = self.parse_identifier()?;
                 AlterTableOperation::DropForeignKey { name }
+            } else if self.parse_keyword(Keyword::INDEX) {
+                let name = self.parse_identifier()?;
+                AlterTableOperation::DropIndex { name }
             } else if self.parse_keyword(Keyword::PROJECTION)
                 && dialect_of!(self is ClickHouseDialect|GenericDialect)
             {
diff --git a/tests/sqlparser_mysql.rs b/tests/sqlparser_mysql.rs
index b1b7d539..540348ff 100644
--- a/tests/sqlparser_mysql.rs
+++ b/tests/sqlparser_mysql.rs
@@ -4025,3 +4025,13 @@ fn parse_drop_index() {
         _ => unreachable!(),
     }
 }
+
+#[test]
+fn parse_alter_table_drop_index() {
+    assert_matches!(
+        alter_table_op(
+            mysql_and_generic().verified_stmt("ALTER TABLE tab DROP INDEX idx_index")
+        ),
+        AlterTableOperation::DropIndex { name } if name.value == "idx_index"
+    );
+}