adding tests for converting rows to different data types

Author: dantownsend

piccolo/query/methods/alter.py

@@ -92,16 +92,18 @@ def querystring(self) -> QueryString:
 
 
 @dataclass
-class SetColumnType(AlterColumnStatement):
-    __slots__ = ("column_name", "column")
+class SetColumnType:
+    __slots__ = ("old_column", "new_column")
 
-    column_name: str
-    column: Column
+    old_column: Column
+    new_column: Column
 
     @property
     def querystring(self) -> QueryString:
+        self.new_column._meta._table = self.old_column._meta.table
+        column_name = self.old_column._meta.name
         return QueryString(
-            f"ALTER COLUMN {self.column_name} TYPE {self.column.column_type}"
+            f"ALTER COLUMN {column_name} TYPE {self.new_column.column_type}"
         )
 
 
@@ -349,12 +351,12 @@ def rename_column(
         self._rename_columns.append(RenameColumn(column, new_name))
         return self
 
-    def set_column_type(self, column_name: str, column: Column) -> Alter:
+    def set_column_type(self, old_column: Column, new_column: Column) -> Alter:
         """
         Change the type of a column.
         """
         self._set_column_type.append(
-            SetColumnType(column_name=column_name, column=column)
+            SetColumnType(old_column=old_column, new_column=new_column)
         )
         return self
 

tests/table/test_alter.py

@@ -1,6 +1,7 @@
+from piccolo.columns.column_types import Varchar
 from unittest import TestCase
 
-from piccolo.columns import Integer, Numeric
+from piccolo.columns import BigInt, Integer, Numeric
 from piccolo.table import Table
 
 from ..base import DBTestCase, postgres_only
@@ -113,7 +114,6 @@ def test_unique(self):
         self.assertTrue(len(response), 2)
 
 
-# TODO - make it work for SQLite. Should work.
 @postgres_only
 class TestMultiple(DBTestCase):
     """
@@ -137,6 +137,61 @@ def test_multiple(self):
         self.assertTrue("column_b" in column_names)
 
 
+@postgres_only
+class TestSetColumnType(DBTestCase):
+    def test_integer_to_bigint(self):
+        """
+        Test converting an Integer column to BigInt.
+        """
+        self.insert_row()
+
+        alter_query = Band.alter().set_column_type(
+            old_column=Band.popularity, new_column=BigInt()
+        )
+        alter_query.run_sync()
+
+        query = """
+            SELECT data_type FROM information_schema.columns
+            WHERE table_name = 'band'
+            AND table_catalog = 'piccolo'
+            AND column_name = 'popularity'
+            """
+
+        response = Band.raw(query).run_sync()
+        self.assertEqual(response[0]["data_type"].upper(), "BIGINT")
+
+        popularity = (
+            Band.select(Band.popularity).first().run_sync()["popularity"]
+        )
+        self.assertEqual(popularity, 1000)
+
+    def test_integer_to_varchar(self):
+        """
+        Test converting an Integer column to Varchar.
+        """
+        self.insert_row()
+
+        alter_query = Band.alter().set_column_type(
+            old_column=Band.popularity, new_column=Varchar()
+        )
+        alter_query.run_sync()
+
+        query = """
+            SELECT data_type FROM information_schema.columns
+            WHERE table_name = 'band'
+            AND table_catalog = 'piccolo'
+            AND column_name = 'popularity'
+            """
+
+        response = Band.raw(query).run_sync()
+        self.assertEqual(response[0]["data_type"].upper(), "CHARACTER VARYING")
+
+        popularity = (
+            Band.select(Band.popularity).first().run_sync()["popularity"]
+        )
+        self.assertEqual(popularity, "1000")
+
+
 @postgres_only
 class TestSetNull(DBTestCase):
     def test_set_null(self):