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 (file)
index 0000000..9ac8257
--- /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 94f265ebed1d0f45d5161a9c7455da20e6742b4f..32b845848da51c6ac26f61a9b250bca704315d0b 100644 (file)
--- 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 f8d9d548862643907d3782c8a862632f4dbc9854..30e7f79a2933410d783b8e0fe9d2d4f56a6b36ff 100644 (file)
--- 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(