1  """
 2  Embedded module
 3  """
 4  
 5  from .rdbms import RDBMS
 6  
 7  
 8  class Embedded(RDBMS):
 9      """
10      Base class for embedded relational databases. An embedded relational database stores all content in a local file.
11      """
12  
13      def __init__(self, config):
14          """
15          Creates a new Database.
16  
17          Args:
18              config: database configuration parameters
19          """
20  
21          super().__init__(config)
22  
23          # Path to database file
24          self.path = None
25  
26      def load(self, path):
27          # Call parent logic
28          super().load(path)
29  
30          # Store path reference
31          self.path = path
32  
33      def save(self, path):
34          # Temporary database
35          if not self.path:
36              # Save temporary database
37              self.connection.commit()
38  
39              # Copy data from current to new
40              connection = self.copy(path)
41  
42              # Close temporary database
43              self.connection.close()
44  
45              # Point connection to new connection
46              self.session(connection=connection)
47              self.path = path
48  
49          # Paths are equal, commit changes
50          elif self.path == path:
51              self.connection.commit()
52  
53          # New path is different from current path, copy data and continue using current connection
54          else:
55              self.copy(path).close()
56  
57      def jsonprefix(self):
58          # Return json column prefix
59          return "json_extract(data"
60  
61      def jsoncolumn(self, name):
62          # Generate json column using json_extract function
63          return f"json_extract(data, '$.{name}')"
64  
65      def copy(self, path):
66          """
67          Copies the current database into path.
68  
69          Args:
70              path: path to write database
71  
72          Returns:
73              new connection with data copied over
74          """
75  
76          raise NotImplementedError