Added parameters if_exists and if_not_exists for index operations.

Fixes: #151

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### Description
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As mentioned in #151, IF EXISTS/IF NOT EXISTS syntax was implemented in SQLAlchemy 2.0. This request adds an ability to use them for index operations.

If the issue implies to implement all the possible cases with these directives, I could continue working on it 🙂

### Checklist
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This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [x] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Closes: #1260
Pull-request: #1260
Pull-request-sha: 5ed62d1

Change-Id: Ic0fec21e20d4a868e9e29275e540f3e09918d1ff

alembic/ddl/impl.py

@@ -379,8 +379,8 @@ def drop_table(self, table: Table) -> None:
             table, self.connection, checkfirst=False, _ddl_runner=self
         )
 
-    def create_index(self, index: Index) -> None:
-        self._exec(schema.CreateIndex(index))
+    def create_index(self, index: Index, **kw: Any) -> None:
+        self._exec(schema.CreateIndex(index, **kw))
 
     def create_table_comment(self, table: Table) -> None:
         self._exec(schema.SetTableComment(table))
@@ -391,8 +391,8 @@ def drop_table_comment(self, table: Table) -> None:
     def create_column_comment(self, column: ColumnElement[Any]) -> None:
         self._exec(schema.SetColumnComment(column))
 
-    def drop_index(self, index: Index) -> None:
-        self._exec(schema.DropIndex(index))
+    def drop_index(self, index: Index, **kw: Any) -> None:
+        self._exec(schema.DropIndex(index, **kw))
 
     def bulk_insert(
         self,

alembic/ddl/mssql.py

@@ -170,7 +170,7 @@ def alter_column(  # type:ignore[override]
                 table_name, column_name, schema=schema, name=name
             )
 
-    def create_index(self, index: Index) -> None:
+    def create_index(self, index: Index, **kw: Any) -> None:
         # this likely defaults to None if not present, so get()
         # should normally not return the default value.  being
         # defensive in any case
@@ -179,7 +179,7 @@ def create_index(self, index: Index) -> None:
         for col in mssql_include:
             if col not in index.table.c:
                 index.table.append_column(Column(col, sqltypes.NullType))
-        self._exec(CreateIndex(index))
+        self._exec(CreateIndex(index, **kw))
 
     def bulk_insert(  # type:ignore[override]
         self, table: Union[TableClause, Table], rows: List[dict], **kw: Any

alembic/ddl/postgresql.py

@@ -80,15 +80,17 @@ class PostgresqlImpl(DefaultImpl):
     )
     identity_attrs_ignore = ("on_null", "order")
 
-    def create_index(self, index):
+    def create_index(self, index: Index, **kw: Any) -> None:
         # this likely defaults to None if not present, so get()
         # should normally not return the default value.  being
         # defensive in any case
         postgresql_include = index.kwargs.get("postgresql_include", None) or ()
         for col in postgresql_include:
-            if col not in index.table.c:
-                index.table.append_column(Column(col, sqltypes.NullType))
-        self._exec(CreateIndex(index))
+            if col not in index.table.c:  # type: ignore[union-attr]
+                index.table.append_column(  # type: ignore[union-attr]
+                    Column(col, sqltypes.NullType)
+                )
+        self._exec(CreateIndex(index, **kw))
 
     def prep_table_for_batch(self, batch_impl, table):
         for constraint in table.constraints:

alembic/op.pyi

@@ -646,6 +646,7 @@ def create_index(
     *,
     schema: Optional[str] = None,
     unique: bool = False,
+    if_not_exists: Optional[bool] = None,
     **kw: Any,
 ) -> None:
     r"""Issue a "create index" instruction using the current
@@ -675,20 +676,24 @@ def create_index(
      :class:`~sqlalchemy.sql.elements.quoted_name`.
     :param unique: If True, create a unique index.
 
-    :param quote:
-        Force quoting of this column's name on or off, corresponding
-        to ``True`` or ``False``. When left at its default
-        of ``None``, the column identifier will be quoted according to
-        whether the name is case sensitive (identifiers with at least one
-        upper case character are treated as case sensitive), or if it's a
-        reserved word. This flag is only needed to force quoting of a
-        reserved word which is not known by the SQLAlchemy dialect.
+    :param quote: Force quoting of this column's name on or off,
+     corresponding to ``True`` or ``False``. When left at its default
+     of ``None``, the column identifier will be quoted according to
+     whether the name is case sensitive (identifiers with at least one
+     upper case character are treated as case sensitive), or if it's a
+     reserved word. This flag is only needed to force quoting of a
+     reserved word which is not known by the SQLAlchemy dialect.
+
+    :param if_not_exists: If True, adds IF NOT EXISTS operator when
+     creating the new index.
+
+     .. versionadded:: 1.12.0
 
     :param \**kw: Additional keyword arguments not mentioned above are
-        dialect specific, and passed in the form
-        ``<dialectname>_<argname>``.
-        See the documentation regarding an individual dialect at
-        :ref:`dialect_toplevel` for detail on documented arguments.
+     dialect specific, and passed in the form
+     ``<dialectname>_<argname>``.
+     See the documentation regarding an individual dialect at
+     :ref:`dialect_toplevel` for detail on documented arguments.
 
     """
 
@@ -955,6 +960,7 @@ def drop_index(
     table_name: Optional[str] = None,
     *,
     schema: Optional[str] = None,
+    if_exists: Optional[bool] = None,
     **kw: Any,
 ) -> None:
     r"""Issue a "drop index" instruction using the current
@@ -971,11 +977,17 @@ def drop_index(
      quoting of the schema outside of the default behavior, use
      the SQLAlchemy construct
      :class:`~sqlalchemy.sql.elements.quoted_name`.
+
+    :param if_exists: If True, adds IF EXISTS operator when
+     dropping the index.
+
+     .. versionadded:: 1.12.0
+
     :param \**kw: Additional keyword arguments not mentioned above are
-        dialect specific, and passed in the form
-        ``<dialectname>_<argname>``.
-        See the documentation regarding an individual dialect at
-        :ref:`dialect_toplevel` for detail on documented arguments.
+     dialect specific, and passed in the form
+     ``<dialectname>_<argname>``.
+     See the documentation regarding an individual dialect at
+     :ref:`dialect_toplevel` for detail on documented arguments.
 
     """
 
@@ -1228,7 +1240,7 @@ def invoke(operation: MigrateOperation) -> Any:
 
 def register_operation(
     name: str, sourcename: Optional[str] = None
-) -> Callable[..., Any]:
+) -> Callable[[_T], _T]:
     """Register a new operation for this class.
 
     This method is normally used to add new operations

alembic/operations/base.py

@@ -1035,6 +1035,7 @@ def create_index(
             *,
             schema: Optional[str] = None,
             unique: bool = False,
+            if_not_exists: Optional[bool] = None,
             **kw: Any,
         ) -> None:
             r"""Issue a "create index" instruction using the current
@@ -1064,20 +1065,24 @@ def create_index(
              :class:`~sqlalchemy.sql.elements.quoted_name`.
             :param unique: If True, create a unique index.
 
-            :param quote:
-                Force quoting of this column's name on or off, corresponding
-                to ``True`` or ``False``. When left at its default
-                of ``None``, the column identifier will be quoted according to
-                whether the name is case sensitive (identifiers with at least one
-                upper case character are treated as case sensitive), or if it's a
-                reserved word. This flag is only needed to force quoting of a
-                reserved word which is not known by the SQLAlchemy dialect.
+            :param quote: Force quoting of this column's name on or off,
+             corresponding to ``True`` or ``False``. When left at its default
+             of ``None``, the column identifier will be quoted according to
+             whether the name is case sensitive (identifiers with at least one
+             upper case character are treated as case sensitive), or if it's a
+             reserved word. This flag is only needed to force quoting of a
+             reserved word which is not known by the SQLAlchemy dialect.
+
+            :param if_not_exists: If True, adds IF NOT EXISTS operator when
+             creating the new index.
+
+             .. versionadded:: 1.12.0
 
             :param \**kw: Additional keyword arguments not mentioned above are
-                dialect specific, and passed in the form
-                ``<dialectname>_<argname>``.
-                See the documentation regarding an individual dialect at
-                :ref:`dialect_toplevel` for detail on documented arguments.
+             dialect specific, and passed in the form
+             ``<dialectname>_<argname>``.
+             See the documentation regarding an individual dialect at
+             :ref:`dialect_toplevel` for detail on documented arguments.
 
             """  # noqa: E501
             ...
@@ -1359,6 +1364,7 @@ def drop_index(
             table_name: Optional[str] = None,
             *,
             schema: Optional[str] = None,
+            if_exists: Optional[bool] = None,
             **kw: Any,
         ) -> None:
             r"""Issue a "drop index" instruction using the current
@@ -1375,11 +1381,17 @@ def drop_index(
              quoting of the schema outside of the default behavior, use
              the SQLAlchemy construct
              :class:`~sqlalchemy.sql.elements.quoted_name`.
+
+            :param if_exists: If True, adds IF EXISTS operator when
+             dropping the index.
+
+             .. versionadded:: 1.12.0
+
             :param \**kw: Additional keyword arguments not mentioned above are
-                dialect specific, and passed in the form
-                ``<dialectname>_<argname>``.
-                See the documentation regarding an individual dialect at
-                :ref:`dialect_toplevel` for detail on documented arguments.
+             dialect specific, and passed in the form
+             ``<dialectname>_<argname>``.
+             See the documentation regarding an individual dialect at
+             :ref:`dialect_toplevel` for detail on documented arguments.
 
             """  # noqa: E501
             ...

alembic/operations/batch.py

@@ -185,11 +185,11 @@ def drop_constraint(self, const: Constraint) -> None:
     def rename_table(self, *arg, **kw):
         self.batch.append(("rename_table", arg, kw))
 
-    def create_index(self, idx: Index) -> None:
-        self.batch.append(("create_index", (idx,), {}))
+    def create_index(self, idx: Index, **kw: Any) -> None:
+        self.batch.append(("create_index", (idx,), kw))
 
-    def drop_index(self, idx: Index) -> None:
-        self.batch.append(("drop_index", (idx,), {}))
+    def drop_index(self, idx: Index, **kw: Any) -> None:
+        self.batch.append(("drop_index", (idx,), kw))
 
     def create_table_comment(self, table):
         self.batch.append(("create_table_comment", (table,), {}))

alembic/operations/ops.py

@@ -876,13 +876,15 @@ def __init__(
         *,
         schema: Optional[str] = None,
         unique: bool = False,
+        if_not_exists: Optional[bool] = None,
         **kw: Any,
     ) -> None:
         self.index_name = index_name
         self.table_name = table_name
         self.columns = columns
         self.schema = schema
         self.unique = unique
+        self.if_not_exists = if_not_exists
         self.kw = kw
 
     def reverse(self) -> DropIndexOp:
@@ -928,6 +930,7 @@ def create_index(
         *,
         schema: Optional[str] = None,
         unique: bool = False,
+        if_not_exists: Optional[bool] = None,
         **kw: Any,
     ) -> None:
         r"""Issue a "create index" instruction using the current
@@ -957,24 +960,34 @@ def create_index(
          :class:`~sqlalchemy.sql.elements.quoted_name`.
         :param unique: If True, create a unique index.
 
-        :param quote:
-            Force quoting of this column's name on or off, corresponding
-            to ``True`` or ``False``. When left at its default
-            of ``None``, the column identifier will be quoted according to
-            whether the name is case sensitive (identifiers with at least one
-            upper case character are treated as case sensitive), or if it's a
-            reserved word. This flag is only needed to force quoting of a
-            reserved word which is not known by the SQLAlchemy dialect.
+        :param quote: Force quoting of this column's name on or off,
+         corresponding to ``True`` or ``False``. When left at its default
+         of ``None``, the column identifier will be quoted according to
+         whether the name is case sensitive (identifiers with at least one
+         upper case character are treated as case sensitive), or if it's a
+         reserved word. This flag is only needed to force quoting of a
+         reserved word which is not known by the SQLAlchemy dialect.
+
+        :param if_not_exists: If True, adds IF NOT EXISTS operator when
+         creating the new index.
+
+         .. versionadded:: 1.12.0
 
         :param \**kw: Additional keyword arguments not mentioned above are
-            dialect specific, and passed in the form
-            ``<dialectname>_<argname>``.
-            See the documentation regarding an individual dialect at
-            :ref:`dialect_toplevel` for detail on documented arguments.
+         dialect specific, and passed in the form
+         ``<dialectname>_<argname>``.
+         See the documentation regarding an individual dialect at
+         :ref:`dialect_toplevel` for detail on documented arguments.
 
         """
         op = cls(
-            index_name, table_name, columns, schema=schema, unique=unique, **kw
+            index_name,
+            table_name,
+            columns,
+            schema=schema,
+            unique=unique,
+            if_not_exists=if_not_exists,
+            **kw,
         )
         return operations.invoke(op)
 
@@ -1016,12 +1029,14 @@ def __init__(
         table_name: Optional[str] = None,
         *,
         schema: Optional[str] = None,
+        if_exists: Optional[bool] = None,
         _reverse: Optional[CreateIndexOp] = None,
         **kw: Any,
     ) -> None:
         self.index_name = index_name
         self.table_name = table_name
         self.schema = schema
+        self.if_exists = if_exists
         self._reverse = _reverse
         self.kw = kw
 
@@ -1065,6 +1080,7 @@ def drop_index(
         table_name: Optional[str] = None,
         *,
         schema: Optional[str] = None,
+        if_exists: Optional[bool] = None,
         **kw: Any,
     ) -> None:
         r"""Issue a "drop index" instruction using the current
@@ -1081,14 +1097,26 @@ def drop_index(
          quoting of the schema outside of the default behavior, use
          the SQLAlchemy construct
          :class:`~sqlalchemy.sql.elements.quoted_name`.
+
+        :param if_exists: If True, adds IF EXISTS operator when
+         dropping the index.
+
+         .. versionadded:: 1.12.0
+
         :param \**kw: Additional keyword arguments not mentioned above are
-            dialect specific, and passed in the form
-            ``<dialectname>_<argname>``.
-            See the documentation regarding an individual dialect at
-            :ref:`dialect_toplevel` for detail on documented arguments.
+         dialect specific, and passed in the form
+         ``<dialectname>_<argname>``.
+         See the documentation regarding an individual dialect at
+         :ref:`dialect_toplevel` for detail on documented arguments.
 
         """
-        op = cls(index_name, table_name=table_name, schema=schema, **kw)
+        op = cls(
+            index_name,
+            table_name=table_name,
+            schema=schema,
+            if_exists=if_exists,
+            **kw,
+        )
         return operations.invoke(op)
 
     @classmethod