Take separator into account when computing maximum schema name prefix length

Author: Photonios

psqlextra/schema.py

@@ -71,9 +71,9 @@ def create_time_based(
         """
 
         suffix = timezone.now().strftime("%Y%m%d%H%m%S")
-        cls._verify_generated_name_length(prefix, suffix)
+        name = cls._create_generated_name(prefix, suffix)
 
-        return cls.create(f"{prefix}_{suffix}", using=using)
+        return cls.create(name, using=using)
 
     @classmethod
     def create_random(
@@ -91,9 +91,9 @@ def create_random(
         """
 
         suffix = os.urandom(4).hex()
-        cls._verify_generated_name_length(prefix, suffix)
+        name = cls._create_generated_name(prefix, suffix)
 
-        return cls.create(f"{prefix}_{suffix}", using=using)
+        return cls.create(name, using=using)
 
     @classmethod
     def delete_and_create(
@@ -160,14 +160,18 @@ def delete(
             schema_editor.delete_schema(self.name, cascade=cascade)
 
     @classmethod
-    def _verify_generated_name_length(cls, prefix: str, suffix: str) -> None:
-        max_prefix_length = cls.NAME_MAX_LENGTH - len(suffix)
+    def _create_generated_name(cls, prefix: str, suffix: str) -> str:
+        separator = "_"
+        generated_name = f"{prefix}{separator}{suffix}"
+        max_prefix_length = cls.NAME_MAX_LENGTH - len(suffix) - len(separator)
 
-        if len(prefix) > max_prefix_length:
+        if len(generated_name) > cls.NAME_MAX_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."
+                f"Schema prefix '{prefix}' is longer than {max_prefix_length} characters. Together with the separator and generated suffix of {len(suffix)} characters, the name would exceed Postgres's limit of {cls.NAME_MAX_LENGTH} characters."
             )
 
+        return generated_name
+
 
 PostgresSchema.default = PostgresSchema("public")
 

tests/test_schema.py

@@ -57,9 +57,9 @@ def test_postgres_schema_create_time_based():
 def test_postgres_schema_create_time_based_long_prefix():
     with pytest.raises(ValidationError) as exc_info:
         with freezegun.freeze_time("2023-04-07 13:37:23.4"):
-            PostgresSchema.create_time_based("a" * 100)
+            PostgresSchema.create_time_based("a" * 49)
 
-    assert "is longer than 49 characters" in str(exc_info.value)
+    assert "is longer than 48 characters" in str(exc_info.value)
 
 
 def test_postgres_schema_create_random():
@@ -74,9 +74,9 @@ def test_postgres_schema_create_random():
 
 def test_postgres_schema_create_random_long_prefix():
     with pytest.raises(ValidationError) as exc_info:
-        PostgresSchema.create_random("a" * 100)
+        PostgresSchema.create_random("a" * 55)
 
-    assert "is longer than 55 characters" in str(exc_info.value)
+    assert "is longer than 54 characters" in str(exc_info.value)
 
 
 def test_postgres_schema_delete_and_create():