Check for database file's DB version (via user_version PRAGMA).

[plomtask] / plomtask / db.py

diff --git a/plomtask/db.py b/plomtask/db.py
index dfb388b7ec6ed9317f19a788336025a96e4c745e..dd2ee2452a7480878c47b38f2669c08cee229ca6 100644 (file)
--- a/plomtask/db.py
+++ b/plomtask/db.py
@@ -1,11 +1,12 @@
 """Database management."""
 from os.path import isfile
 from difflib import Differ
-from sqlite3 import connect as sql_connect, Cursor
+from sqlite3 import connect as sql_connect, Cursor, Row
 from typing import Any, Dict
 from plomtask.exceptions import HandledException
 
 PATH_DB_SCHEMA = 'scripts/init.sql'
+EXPECTED_DB_VERSION = 0
 
 
 class DatabaseFile:  # pylint: disable=too-few-public-methods
@@ -23,11 +24,22 @@ class DatabaseFile:  # pylint: disable=too-few-public-methods
         self._check()
 
     def _check(self) -> None:
-        """Check file exists, and is of proper schema."""
+        """Check file exists, and is of proper DB version and schema."""
         self.exists = isfile(self.path)
         if self.exists:
+            self._validate_user_version()
             self._validate_schema()
 
+    def _validate_user_version(self) -> None:
+        """Compare DB user_version with EXPECTED_DB_VERSION."""
+        sql_for_db_version = 'PRAGMA user_version'
+        with sql_connect(self.path) as conn:
+            db_version = list(conn.execute(sql_for_db_version))[0][0]
+            if db_version != EXPECTED_DB_VERSION:
+                msg = f'Wrong DB version, expected '\
+                        f'{EXPECTED_DB_VERSION}, got {db_version}.'
+                raise HandledException(msg)
+
     def _validate_schema(self) -> None:
         """Compare found schema with what's stored at PATH_DB_SCHEMA."""
         sql_for_schema = 'SELECT sql FROM sqlite_master ORDER BY sql'
@@ -67,12 +79,77 @@ class DatabaseConnection:
         """Close DB connection."""
         self.conn.close()
 
+    def rewrite_relations(self, table_name: str, key: str, target: int,
+                          rows: list[list[Any]]) -> None:
+        """Rewrite relations in table_name to target, with rows values."""
+        self.delete_where(table_name, key, target)
+        for row in rows:
+            values = tuple([target] + row)
+            q_marks = self.__class__.q_marks_from_values(values)
+            self.exec(f'INSERT INTO {table_name} VALUES {q_marks}', values)
+
+    def row_where(self, table_name: str, key: str,
+                  target: int | str) -> list[Row]:
+        """Return list of Rows at table where key == target."""
+        return list(self.exec(f'SELECT * FROM {table_name} WHERE {key} = ?',
+                              (target,)))
+
+    def column_where(self, table_name: str, column: str, key: str,
+                     target: int | str) -> list[Any]:
+        """Return column of table where key == target."""
+        return [row[0] for row in
+                self.exec(f'SELECT {column} FROM {table_name} '
+                          f'WHERE {key} = ?', (target,))]
+
+    def column_all(self, table_name: str, column: str) -> list[Any]:
+        """Return complete column of table."""
+        return [row[0] for row in
+                self.exec(f'SELECT {column} FROM {table_name}')]
+
+    def delete_where(self, table_name: str, key: str, target: int) -> None:
+        """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)) + ')'
+
 
 class BaseModel:
     """Template for most of the models we use/derive from the DB."""
     table_name = ''
     to_save: list[str] = []
     id_: None | int | str
+    id_type: type[Any] = int
+
+    @classmethod
+    def from_table_row(cls, db_conn: DatabaseConnection,
+                       row: Row | list[Any]) -> Any:
+        """Make from DB row, write to DB cache."""
+        obj = cls(*row)
+        assert isinstance(obj.id_, cls.id_type)
+        cache = getattr(db_conn, f'cached_{cls.table_name}')
+        cache[obj.id_] = obj
+        return obj
+
+    @classmethod
+    def _by_id(cls,
+               db_conn: DatabaseConnection,
+               id_: int | str) -> tuple[Any, bool]:
+        """Return instance found by ID, or None, and if from cache or not."""
+        from_cache = False
+        obj = None
+        cache = getattr(db_conn, f'cached_{cls.table_name}')
+        if id_ in cache.keys():
+            obj = cache[id_]
+            from_cache = True
+        else:
+            for row in db_conn.row_where(cls.table_name, 'id', id_):
+                obj = cls.from_table_row(db_conn, row)
+                cache[id_] = obj
+                break
+        return obj, from_cache
 
     def set_int_id(self, id_: int | None) -> None:
         """Set id_ if >= 1 or None, else fail."""
@@ -84,11 +161,11 @@ class BaseModel:
     def save_core(self, db_conn: DatabaseConnection,
                   update_with_lastrowid: bool = True) -> None:
         """Write bare-bones self (sans connected items), ensuring self.id_."""
-        q_marks = ','.join(['?'] * (len(self.to_save) + 1))
         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})',
+        cursor = db_conn.exec(f'REPLACE INTO {table_name} VALUES {q_marks}',
                               values)
         if update_with_lastrowid:
             self.id_ = cursor.lastrowid