Class DBTable

source code

     object --+                
              |                
 ligolw.Element --+            
                  |            
ligolw.EmptyElement --+        
                      |        
           ligolw.Table --+    
                          |    
             object --+   |    
                      |   |    
                   list --+    
                          |    
                table.Table --+
                              |
                             DBTable

Known Subclasses:

• ProcessParamsTable
• , TimeSlideTable

A special version of the Table class using an SQL database for storage. Many of the features of the Table class are not available here, but instead the user can use SQL to query the table's contents.

The constraints attribute can be set to a text string that will be added to the table's CREATE statement where constraints go, for example you might wish to set this to "PRIMARY KEY (event_id)" for a table with an event_id column.

Note: because the table is stored in an SQL database, the use of this class imposes the restriction that table names be unique within a document.

Also note that at the present time there is really only proper support for the pre-defined tables in the lsctables module. It is possible to load unrecognized tables into a database from LIGO Light Weight XML files, but without developer intervention there is no way to indicate the constraints that should be imposed on the columns, for example which columns should be used as primary keys and so on. This can result in poor query performance. It is also possible to extract a database' contents to a LIGO Light Weight XML file even when the database contains unrecognized tables, but without developer intervention the column types will be guessed using a generic mapping of SQL types to LIGO Light Weight types.

Each instance of this class must be connected to a database. The (Python DBAPI 2.0 compatible) connection object is passed to the class via the connection parameter at instance creation time.

Example:

>>> import sqlite3
>>> connection = sqlite3.connection()
>>> tbl = dbtables.DBTable(AttributesImpl({u"Name": u"process:table"}), connection = connection)

A custom content handler must be created in order to pass the connection keyword argument to the DBTable class when instances are created, since the default content handler does not do this. See the use_in() function defined in this module for information on how to create such a content handler

If a custom glue.ligolw.Table subclass is defined in glue.ligolw.lsctables whose name matches the name of the DBTable being constructed, the lsctables class is added to the list of parent classes. This allows the lsctables class' methods to be used with the DBTable instances but not all of the methods will necessarily work with the database-backed version of the class. Your mileage may vary.

>>> import lsctables
>>> tbl = lsctables.New(lsctables.ProcessTable)
>>> print(tbl.sync_next_id())
process:process_id:0