sql.py

#!/usr/bin/env python3
###############################################################################
#
# MIT License
#
# Copyright (c) 2022 Advanced Micro Devices, Inc.
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# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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""" Database resource manager """
import mysql.connector  # pylint: disable=unused-import

from mysql.connector.connection import MySQLConnection
from mysql.connector.cursor import MySQLCursor


class DbConnection():
  """ Resource manager class for a SQL connection """

  def __init__(self):
    '''
        Importing in a function may be a thorny subject.
        Please see
        http://stackoverflow.com/questions/477096/python-import-coding-style/4789963#4789963
        for my reason to use this.
        '''
    import os  # pylint: disable=import-outside-toplevel

    self.db_user_name: str
    self.db_user_password: str
    self.db_host_name: str
    self.db_name: str

    if 'TUNA_DB_USER_NAME' in os.environ:
      self.db_user_name = os.environ['TUNA_DB_USER_NAME']
    else:
      self.db_user_name = ''
    if 'TUNA_DB_USER_PASSWORD' in os.environ:
      self.db_user_password = os.environ['TUNA_DB_USER_PASSWORD']
    else:
      self.db_user_password = ''
    if 'TUNA_DB_HOSTNAME' in os.environ:
      self.db_host_name = os.environ['TUNA_DB_HOSTNAME']
    else:
      self.db_host_name = 'localhost'
    if 'TUNA_DB_NAME' in os.environ:
      self.db_name = os.environ['TUNA_DB_NAME']
    else:
      self.db_name = ''

    self.connection: MySQLConnection = None

  def get_connection(self) -> MySQLConnection:
    """ return a cached connection if one exists, else create a new one
    and return that instead """
    if self.connection is not None and self.connection.is_connected():
      return self.connection

    self.connection = mysql.connector.connect(user=self.db_user_name,
                                              password=self.db_user_password,
                                              host=self.db_host_name,
                                              database=self.db_name)
    self.connection.autocommit = False
    if not self.connection.is_connected():
      raise ValueError('Could not connect to the DB instance')
    return self.connection

  def close_connection(self) -> bool:
    """ Close a SQL connection after commiting the changes """
    self.connection.commit()
    self.connection.close()
    return True

  def __enter__(self):
    return self.get_connection()

  def __exit__(self, type_t, value, traceback):
    self.close_connection()


class DbCursor():
  """Resource manager class for a SQL cursor"""

  def __init__(self):
    self.cnx: DbConnection = None
    self.sql_connection: MySQLConnection = None
    self.cur: MySQLCursor = None

  def __enter__(self) -> MySQLCursor:
    self.cnx = DbConnection()
    self.sql_connection = self.cnx.get_connection()
    self.cur = self.sql_connection.cursor()
    return self.cur

  def __exit__(self, type_t, value, traceback):
    self.cur.close()
    self.cnx.close_connection()