prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Function to handle deleting schemas
  **Problem**
  <!-- Please provide a clear and concise description of the problem that this feature request is designed to solve.-->
  Users might want to delete schemas. We don't currently support this.
  
  **Proposed solution**
  <!-- A clear and concise description of your proposed solution or feature. -->
  A function that handles deleting of schemas in the database. We should raise an error if there is anything outside of the schema referencing the schema.
  
  **Additional context**
  <!-- Add any other context or screenshots about the feature request here.-->
  This should be in the `db` module.
  
  </issue>
  <code>
  [start of db/schemas.py]
  1 import logging
  2 import warnings
  3 from sqlalchemy.schema import CreateSchema
  4 from sqlalchemy import inspect, MetaData, select, and_, not_, or_, Table
  5 
  6 from db import types
  7 
  8 logger = logging.getLogger(__name__)
  9 
  10 TYPES_SCHEMA = types.base.SCHEMA
  11 
  12 EXCLUDED_SCHEMATA = [TYPES_SCHEMA, "information_schema"]
  13 
  14 
  15 def get_schema_name_from_oid(oid, engine):
  16     return reflect_schema(engine, oid=oid)["name"]
  17 
  18 
  19 def get_schema_oid_from_name(name, engine):
  20     return reflect_schema(engine, name=name)["oid"]
  21 
  22 
  23 def reflect_schema(engine, name=None, oid=None):
  24     # If we have both arguments, the behavior is undefined.
  25     try:
  26         assert name is None or oid is None
  27     except AssertionError as e:
  28         logger.error("ERROR:  Only one of 'name' or 'oid' can be given!")
  29         raise e
  30     metadata = MetaData()
  31     with warnings.catch_warnings():
  32         warnings.filterwarnings("ignore", message="Did not recognize type")
  33         pg_namespace = Table("pg_namespace", metadata, autoload_with=engine)
  34     sel = (
  35         select(pg_namespace.c.oid, pg_namespace.c.nspname.label("name"))
  36         .where(or_(pg_namespace.c.nspname == name, pg_namespace.c.oid == oid))
  37     )
  38     with engine.begin() as conn:
  39         schema_info = conn.execute(sel).fetchone()
  40     return schema_info
  41 
  42 
  43 def get_mathesar_schemas(engine):
  44     return [schema for schema, _ in get_mathesar_schemas_with_oids(engine)]
  45 
  46 
  47 def get_mathesar_schemas_with_oids(engine):
  48     metadata = MetaData()
  49     with warnings.catch_warnings():
  50         warnings.filterwarnings("ignore", message="Did not recognize type")
  51         pg_namespace = Table("pg_namespace", metadata, autoload_with=engine)
  52     sel = (
  53         select(pg_namespace.c.nspname.label('schema'), pg_namespace.c.oid)
  54         .where(
  55             and_(
  56                 *[pg_namespace.c.nspname != schema for schema in EXCLUDED_SCHEMATA],
  57                 not_(pg_namespace.c.nspname.like("pg_%"))
  58             )
  59         )
  60     )
  61     with engine.begin() as conn:
  62         result = conn.execute(sel).fetchall()
  63     return result
  64 
  65 
  66 def get_all_schemas(engine):
  67     inspector = inspect(engine)
  68     # We don't need to exclude system schemas (i.e., starting with "pg_")
  69     # since Inspector.get_schema_names already excludes them.  Thus, this
  70     # function actually gets all non-pg-reserved schemas.
  71     return inspector.get_schema_names()
  72 
  73 
  74 def create_schema(schema, engine):
  75     """
  76     This method creates a Postgres schema.
  77     """
  78     if schema not in get_all_schemas(engine):
  79         with engine.begin() as connection:
  80             connection.execute(CreateSchema(schema))
  81
  [end of db/schemas.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/db/schemas.py b/db/schemas.py
  --- a/db/schemas.py
  +++ b/db/schemas.py
  @@ -1,7 +1,11 @@
   import logging
   import warnings
  -from sqlalchemy.schema import CreateSchema
  +from sqlalchemy.schema import CreateSchema, DropSchema
   from sqlalchemy import inspect, MetaData, select, and_, not_, or_, Table
  +from sqlalchemy.exc import InternalError
  +from sqlalchemy.schema import DDLElement
  +from sqlalchemy.ext import compiler
  +from psycopg2.errors import DependentObjectsStillExist
   
   from db import types
   
  @@ -78,3 +82,42 @@
       if schema not in get_all_schemas(engine):
           with engine.begin() as connection:
               connection.execute(CreateSchema(schema))
  +
  +
  +def delete_schema(schema, engine, cascade=False, if_exists=False):
  +    """
  +    This method deletes a Postgres schema.
  +    """
  +    if if_exists and schema not in get_all_schemas(engine):
  +        return
  +
  +    with engine.begin() as connection:
  +        try:
  +            connection.execute(DropSchema(schema, cascade=cascade))
  +        except InternalError as e:
  +            if isinstance(e.orig, DependentObjectsStillExist):
  +                raise e.orig
  +            else:
  +                raise e
  +
  +
  +class RenameSchema(DDLElement):
  +    def __init__(self, schema, rename_to):
  +        self.schema = schema
  +        self.rename_to = rename_to
  +
  +
  +@compiler.compiles(RenameSchema)
  +def compile_rename_schema(element, compiler, **_):
  +    return "ALTER SCHEMA %s RENAME TO %s" % (
  +        element.schema,
  +        element.rename_to
  +    )
  +
  +
  +def rename_schema(schema, engine, rename_to):
  +    """
  +    This method renames a Postgres schema.
  +    """
  +    with engine.begin() as connection:
  +        connection.execute(RenameSchema(schema, rename_to))
  
verification_info: {"golden_diff": "diff --git a/db/schemas.py b/db/schemas.py\n--- a/db/schemas.py\n+++ b/db/schemas.py\n@@ -1,7 +1,11 @@\n import logging\n import warnings\n-from sqlalchemy.schema import CreateSchema\n+from sqlalchemy.schema import CreateSchema, DropSchema\n from sqlalchemy import inspect, MetaData, select, and_, not_, or_, Table\n+from sqlalchemy.exc import InternalError\n+from sqlalchemy.schema import DDLElement\n+from sqlalchemy.ext import compiler\n+from psycopg2.errors import DependentObjectsStillExist\n \n from db import types\n \n@@ -78,3 +82,42 @@\n     if schema not in get_all_schemas(engine):\n         with engine.begin() as connection:\n             connection.execute(CreateSchema(schema))\n+\n+\n+def delete_schema(schema, engine, cascade=False, if_exists=False):\n+    \"\"\"\n+    This method deletes a Postgres schema.\n+    \"\"\"\n+    if if_exists and schema not in get_all_schemas(engine):\n+        return\n+\n+    with engine.begin() as connection:\n+        try:\n+            connection.execute(DropSchema(schema, cascade=cascade))\n+        except InternalError as e:\n+            if isinstance(e.orig, DependentObjectsStillExist):\n+                raise e.orig\n+            else:\n+                raise e\n+\n+\n+class RenameSchema(DDLElement):\n+    def __init__(self, schema, rename_to):\n+        self.schema = schema\n+        self.rename_to = rename_to\n+\n+\n+@compiler.compiles(RenameSchema)\n+def compile_rename_schema(element, compiler, **_):\n+    return \"ALTER SCHEMA %s RENAME TO %s\" % (\n+        element.schema,\n+        element.rename_to\n+    )\n+\n+\n+def rename_schema(schema, engine, rename_to):\n+    \"\"\"\n+    This method renames a Postgres schema.\n+    \"\"\"\n+    with engine.begin() as connection:\n+        connection.execute(RenameSchema(schema, rename_to))\n", "issue": "Function to handle deleting schemas\n**Problem**\r\n<!-- Please provide a clear and concise description of the problem that this feature request is designed to solve.-->\r\nUsers might want to delete schemas. We don't currently support this.\r\n\r\n**Proposed solution**\r\n<!-- A clear and concise description of your proposed solution or feature. -->\r\nA function that handles deleting of schemas in the database. We should raise an error if there is anything outside of the schema referencing the schema.\r\n\r\n**Additional context**\r\n<!-- Add any other context or screenshots about the feature request here.-->\r\nThis should be in the `db` module.\n", "before_files": [{"content": "import logging\nimport warnings\nfrom sqlalchemy.schema import CreateSchema\nfrom sqlalchemy import inspect, MetaData, select, and_, not_, or_, Table\n\nfrom db import types\n\nlogger = logging.getLogger(__name__)\n\nTYPES_SCHEMA = types.base.SCHEMA\n\nEXCLUDED_SCHEMATA = [TYPES_SCHEMA, \"information_schema\"]\n\n\ndef get_schema_name_from_oid(oid, engine):\n    return reflect_schema(engine, oid=oid)[\"name\"]\n\n\ndef get_schema_oid_from_name(name, engine):\n    return reflect_schema(engine, name=name)[\"oid\"]\n\n\ndef reflect_schema(engine, name=None, oid=None):\n    # If we have both arguments, the behavior is undefined.\n    try:\n        assert name is None or oid is None\n    except AssertionError as e:\n        logger.error(\"ERROR:  Only one of 'name' or 'oid' can be given!\")\n        raise e\n    metadata = MetaData()\n    with warnings.catch_warnings():\n        warnings.filterwarnings(\"ignore\", message=\"Did not recognize type\")\n        pg_namespace = Table(\"pg_namespace\", metadata, autoload_with=engine)\n    sel = (\n        select(pg_namespace.c.oid, pg_namespace.c.nspname.label(\"name\"))\n        .where(or_(pg_namespace.c.nspname == name, pg_namespace.c.oid == oid))\n    )\n    with engine.begin() as conn:\n        schema_info = conn.execute(sel).fetchone()\n    return schema_info\n\n\ndef get_mathesar_schemas(engine):\n    return [schema for schema, _ in get_mathesar_schemas_with_oids(engine)]\n\n\ndef get_mathesar_schemas_with_oids(engine):\n    metadata = MetaData()\n    with warnings.catch_warnings():\n        warnings.filterwarnings(\"ignore\", message=\"Did not recognize type\")\n        pg_namespace = Table(\"pg_namespace\", metadata, autoload_with=engine)\n    sel = (\n        select(pg_namespace.c.nspname.label('schema'), pg_namespace.c.oid)\n        .where(\n            and_(\n                *[pg_namespace.c.nspname != schema for schema in EXCLUDED_SCHEMATA],\n                not_(pg_namespace.c.nspname.like(\"pg_%\"))\n            )\n        )\n    )\n    with engine.begin() as conn:\n        result = conn.execute(sel).fetchall()\n    return result\n\n\ndef get_all_schemas(engine):\n    inspector = inspect(engine)\n    # We don't need to exclude system schemas (i.e., starting with \"pg_\")\n    # since Inspector.get_schema_names already excludes them.  Thus, this\n    # function actually gets all non-pg-reserved schemas.\n    return inspector.get_schema_names()\n\n\ndef create_schema(schema, engine):\n    \"\"\"\n    This method creates a Postgres schema.\n    \"\"\"\n    if schema not in get_all_schemas(engine):\n        with engine.begin() as connection:\n            connection.execute(CreateSchema(schema))\n", "path": "db/schemas.py"}]}