From: Edgar Ramírez Mondragón <edgarrm358@gmail.com>
Date: Thu, 18 Dec 2025 19:58:59 +0000 (-0500)
Subject: Support for `IF EXISTS` in SQL Server 2016 (13.x) and later versions
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=40fc3c90e1fee3f7a19184ab57cca3cbcdfa6da1;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

Support for `IF EXISTS` in SQL Server 2016 (13.x) and later versions

Added support for the ``IF EXISTS`` clause when dropping indexes on SQL
Server 2016 (13.x) and later versions. The :paramref:`.DropIndex.if_exists`
parameter is now honored by the SQL Server dialect, allowing conditional
index drops that will not raise an error if the index does not exist.
Pull request courtesy Edgar Ramírez Mondragón.

Fixes: #13045
Closes: #13046
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/13046
Pull-request-sha: 65dca2055cb403430730b5cf42f0c5f55b23bfb1

Change-Id: Iab95b1a46003b38709a791b8a7c4233dfda5e830
---

diff --git a/doc/build/changelog/unreleased_20/13045.rst b/doc/build/changelog/unreleased_20/13045.rst
new file mode 100644
index 0000000000..9ac8257451
--- /dev/null
+++ b/doc/build/changelog/unreleased_20/13045.rst
@@ -0,0 +1,9 @@
+.. change::
+    :tags: usecase, mssql
+    :tickets: 13045
+
+    Added support for the ``IF EXISTS`` clause when dropping indexes on SQL
+    Server 2016 (13.x) and later versions. The :paramref:`.DropIndex.if_exists`
+    parameter is now honored by the SQL Server dialect, allowing conditional
+    index drops that will not raise an error if the index does not exist.
+    Pull request courtesy Edgar Ramírez Mondragón.
diff --git a/lib/sqlalchemy/dialects/mssql/base.py b/lib/sqlalchemy/dialects/mssql/base.py
index 94f265ebed..32b845848d 100644
--- a/lib/sqlalchemy/dialects/mssql/base.py
+++ b/lib/sqlalchemy/dialects/mssql/base.py
@@ -963,6 +963,7 @@ import codecs
 import datetime
 import operator
 import re
+from typing import Any
 from typing import Literal
 from typing import overload
 from typing import TYPE_CHECKING
@@ -1014,6 +1015,7 @@ from ...types import VARCHAR
 from ...util import update_wrapper
 
 if TYPE_CHECKING:
+    from ...sql.ddl import DropIndex
     from ...sql.dml import DMLState
     from ...sql.selectable import TableClause
 
@@ -2688,11 +2690,13 @@ class MSDDLCompiler(compiler.DDLCompiler):
 
         return text
 
-    def visit_drop_index(self, drop, **kw):
-        return "\nDROP INDEX %s ON %s" % (
-            self._prepared_index_name(drop.element, include_schema=False),
-            self.preparer.format_table(drop.element.table),
+    def visit_drop_index(self, drop: DropIndex, **kw: Any) -> str:
+        index_name = self._prepared_index_name(
+            drop.element, include_schema=False
         )
+        table_name = self.preparer.format_table(drop.element.table)
+        if_exists = " IF EXISTS" if drop.if_exists else ""
+        return f"\nDROP INDEX{if_exists} {index_name} ON {table_name}"
 
     def visit_create_table_as(self, element, **kw):
         prep = self.preparer
diff --git a/test/dialect/mssql/test_compiler.py b/test/dialect/mssql/test_compiler.py
index f8d9d54886..30e7f79a29 100644
--- a/test/dialect/mssql/test_compiler.py
+++ b/test/dialect/mssql/test_compiler.py
@@ -1534,6 +1534,14 @@ class CompileTest(fixtures.TestBase, AssertsCompiledSQL):
             "DROP INDEX idx_foo ON bar.foo",
         )
 
+    def test_drop_index_if_exists(self):
+        m = MetaData()
+        t1 = Table("foo", m, Column("x", Integer), schema="bar")
+        self.assert_compile(
+            schema.DropIndex(Index("idx_foo", t1.c.x), if_exists=True),
+            "DROP INDEX IF EXISTS idx_foo ON bar.foo",
+        )
+
     def test_index_extra_include_1(self):
         metadata = MetaData()
         tbl = Table(