Fixed #25002 -- Used PostgreSQL column type alteration USING clause.

Thanks to Dirk Uys for the report.

django/db/backends/postgresql_psycopg2/schema.py

@@ -5,9 +5,12 @@ from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 
 class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
 
+    sql_alter_column_type = "ALTER COLUMN %(column)s TYPE %(type)s USING %(column)s::%(type)s"
+
     sql_create_sequence = "CREATE SEQUENCE %(sequence)s"
     sql_delete_sequence = "DROP SEQUENCE IF EXISTS %(sequence)s CASCADE"
     sql_set_sequence_max = "SELECT setval('%(sequence)s', MAX(%(column)s)) FROM %(table)s"
+
     sql_create_varchar_index = "CREATE INDEX %(name)s ON %(table)s (%(columns)s varchar_pattern_ops)%(extra)s"
     sql_create_text_index = "CREATE INDEX %(name)s ON %(table)s (%(columns)s text_pattern_ops)%(extra)s"
 

tests/schema/tests.py

@@ -10,6 +10,7 @@ from django.db.models import Model
 from django.db.models.fields import (
     AutoField, BigIntegerField, BinaryField, BooleanField, CharField,
     DateTimeField, IntegerField, PositiveIntegerField, SlugField, TextField,
+    TimeField,
 )
 from django.db.models.fields.related import (
     ForeignKey, ManyToManyField, OneToOneField,
@@ -447,6 +448,19 @@ class SchemaTests(TransactionTestCase):
         with connection.schema_editor() as editor:
             editor.alter_field(Note, old_field, new_field, strict=True)
 
+    def test_alter_text_field_to_time_field(self):
+        """
+        #25002 - Test conversion of text field to time field.
+        """
+        with connection.schema_editor() as editor:
+            editor.create_model(Note)
+        Note.objects.create(info='3:16')
+        old_field = Note._meta.get_field('info')
+        new_field = TimeField(blank=True)
+        new_field.set_attributes_from_name('info')
+        with connection.schema_editor() as editor:
+            editor.alter_field(Note, old_field, new_field, strict=True)
+
     @skipIfDBFeature('interprets_empty_strings_as_nulls')
     def test_alter_textual_field_keep_null_status(self):
         """