From: Christian Heller <c.heller@plomlompom.de>
Date: Fri, 14 Jun 2024 18:03:37 +0000 (+0200)
Subject: Refactor database management code a little bit.
X-Git-Url: https://plomlompom.com/repos/%7B%7B%20web_path%20%7D%7D/decks/process?a=commitdiff_plain;h=4ee3cc797f983d41dae831cb47e2b1a5d4c96f22;p=plomtask

Refactor database management code a little bit.
---

diff --git a/plomtask/db.py b/plomtask/db.py
index bd60968..2077d79 100644
--- a/plomtask/db.py
+++ b/plomtask/db.py
@@ -18,8 +18,9 @@ class UnmigratedDbException(HandledException):
     """To identify case of unmigrated DB file."""
 
 
-class DatabaseFile:  # pylint: disable=too-few-public-methods
+class DatabaseFile:
     """Represents the sqlite3 database's file."""
+    # pylint: disable=too-few-public-methods
 
     def __init__(self, path: str) -> None:
         self.path = path
@@ -38,7 +39,7 @@ class DatabaseFile:  # pylint: disable=too-few-public-methods
     def migrate(cls, path: str) -> DatabaseFile:
         """Apply migrations from_version to EXPECTED_DB_VERSION."""
         migrations = cls._available_migrations()
-        from_version = cls.get_version_of_db(path)
+        from_version = cls._get_version_of_db(path)
         migrations_todo = migrations[from_version+1:]
         for j, filename in enumerate(migrations_todo):
             with sql_connect(path) as conn:
@@ -54,7 +55,7 @@ class DatabaseFile:  # pylint: disable=too-few-public-methods
         """Check file exists, and is of proper DB version and schema."""
         if not isfile(self.path):
             raise NotFoundException
-        if self.user_version != EXPECTED_DB_VERSION:
+        if self._user_version != EXPECTED_DB_VERSION:
             raise UnmigratedDbException()
         self._validate_schema()
 
@@ -86,7 +87,7 @@ class DatabaseFile:  # pylint: disable=too-few-public-methods
         return migrations_list
 
     @staticmethod
-    def get_version_of_db(path: str) -> int:
+    def _get_version_of_db(path: str) -> int:
         """Get DB user_version, fail if outside expected range."""
         sql_for_db_version = 'PRAGMA user_version'
         with sql_connect(path) as conn:
@@ -99,9 +100,11 @@ class DatabaseFile:  # pylint: disable=too-few-public-methods
         return db_version
 
     @property
-    def user_version(self) -> int:
+    def _user_version(self) -> int:
         """Get DB user_version."""
-        return self.__class__.get_version_of_db(self.path)
+        # pylint: disable=protected-access
+        # (since we remain within class)
+        return self.__class__._get_version_of_db(self.path)
 
     def _validate_schema(self) -> None:
         """Compare found schema with what's stored at PATH_DB_SCHEMA."""
@@ -156,8 +159,7 @@ class DatabaseConnection:
     """A single connection to the database."""
 
     def __init__(self, db_file: DatabaseFile) -> None:
-        self.file = db_file
-        self.conn = sql_connect(self.file.path)
+        self.conn = sql_connect(db_file.path)
 
     def commit(self) -> None:
         """Commit SQL transaction."""
@@ -167,6 +169,11 @@ class DatabaseConnection:
         """Add commands to SQL transaction."""
         return self.conn.execute(code, inputs)
 
+    def exec_on_vals(self, code: str, inputs: tuple[Any, ...]) -> Cursor:
+        """Wrapper around .exec appending adequate " (?, …)" to code."""
+        q_marks_from_values = '(' + ','.join(['?'] * len(inputs)) + ')'
+        return self.exec(f'{code} {q_marks_from_values}', inputs)
+
     def close(self) -> None:
         """Close DB connection."""
         self.conn.close()
@@ -183,8 +190,7 @@ class DatabaseConnection:
         self.delete_where(table_name, key, target)
         for row in rows:
             values = tuple(row[:key_index] + [target] + row[key_index:])
-            q_marks = self.__class__.q_marks_from_values(values)
-            self.exec(f'INSERT INTO {table_name} VALUES {q_marks}', values)
+            self.exec_on_vals(f'INSERT INTO {table_name} VALUES', values)
 
     def row_where(self, table_name: str, key: str,
                   target: int | str) -> list[Row]:
@@ -220,11 +226,6 @@ class DatabaseConnection:
         """Delete from table where key == target."""
         self.exec(f'DELETE FROM {table_name} WHERE {key} = ?', (target,))
 
-    @staticmethod
-    def q_marks_from_values(values: tuple[Any]) -> str:
-        """Return placeholder to insert values into SQL code."""
-        return '(' + ','.join(['?'] * len(values)) + ')'
-
 
 BaseModelId = TypeVar('BaseModelId', int, str)
 BaseModelInstance = TypeVar('BaseModelInstance', bound='BaseModel[Any]')
@@ -417,10 +418,9 @@ class BaseModel(Generic[BaseModelId]):
         """
         values = tuple([self.id_] + [getattr(self, key)
                                      for key in self.to_save])
-        q_marks = DatabaseConnection.q_marks_from_values(values)
         table_name = self.table_name
-        cursor = db_conn.exec(f'REPLACE INTO {table_name} VALUES {q_marks}',
-                              values)
+        cursor = db_conn.exec_on_vals(f'REPLACE INTO {table_name} VALUES',
+                                      values)
         if not isinstance(self.id_, str):
             self.id_ = cursor.lastrowid  # type: ignore[assignment]
         self.cache()