Raise specific validation error for schema name prefix + suffix exceeding limit

Author: Photonios

psqlextra/schema.py

@@ -104,8 +104,10 @@ def create_time_based(
                 Name of the database connection to use.
         """
 
-        name_suffix = timezone.now().strftime("%Y%m%d%H%m%s")
-        return cls.create(f"{prefix}_{name_suffix}", using=using)
+        suffix = timezone.now().strftime("%Y%m%d%H%m%s")
+        cls._verify_generated_name_length(prefix, suffix)
+
+        return cls.create(f"{prefix}_{suffix}", using=using)
 
     @classmethod
     def create_random(
@@ -122,8 +124,10 @@ def create_random(
                 Name of the database connection to use.
         """
 
-        name_suffix = os.urandom(4).hex()
-        return cls.create(f"{prefix}_{name_suffix}", using=using)
+        suffix = os.urandom(4).hex()
+        cls._verify_generated_name_length(prefix, suffix)
+
+        return cls.create(f"{prefix}_{suffix}", using=using)
 
     @classmethod
     def delete_and_create(
@@ -201,6 +205,15 @@ def connection(self) -> BaseDatabaseWrapper:
 
         return PostgresSchemaConnectionWrapper(connections[self.using], self)
 
+    @classmethod
+    def _verify_generated_name_length(cls, prefix: str, suffix: str) -> None:
+        max_prefix_length = cls.NAME_MAX_LENGTH - len(suffix)
+
+        if len(prefix) > max_prefix_length:
+            raise ValidationError(
+                f"Schema prefix '{prefix}' is longer than {max_prefix_length} characters. Together with the generated suffix of {len(suffix)} characters, the name would exceed Postgres's limit of {cls.NAME_MAX_LENGTH} characters."
+            )
+
 
 PostgresSchema.default = PostgresSchema("public")
 

tests/test_schema.py

@@ -37,11 +37,13 @@ def test_postgres_schema_does_not_overwrite():
 
 
 def test_postgres_schema_create_max_name_length():
-    with pytest.raises(ValidationError):
+    with pytest.raises(ValidationError) as exc_info:
         PostgresSchema.create(
             "stringthatislongerhtan63charactersforsureabsolutelysurethisislongerthanthat"
         )
 
+    assert "is longer than Postgres's limit" in str(exc_info.value)
+
 
 def test_postgres_schema_create_name_that_requires_escaping():
     # 'table' needs escaping because it conflicts with
@@ -60,6 +62,13 @@ def test_postgres_schema_create_time_based():
     assert _does_schema_exist(schema.name)
 
 
+def test_postgres_schema_create_time_based_long_prefix():
+    with pytest.raises(ValidationError) as exc_info:
+        PostgresSchema.create_time_based("a" * 100)
+
+    assert "is longer than 55 characters" in str(exc_info.value)
+
+
 def test_postgres_schema_create_random():
     schema = PostgresSchema.create_random("myprefix")
 
@@ -70,6 +79,13 @@ def test_postgres_schema_create_random():
     assert _does_schema_exist(schema.name)
 
 
+def test_postgres_schema_create_random_long_prefix():
+    with pytest.raises(ValidationError) as exc_info:
+        PostgresSchema.create_random("a" * 100)
+
+    assert "is longer than 55 characters" in str(exc_info.value)
+
+
 def test_postgres_schema_delete_and_create():
     schema = PostgresSchema.create("test")