Utility functions

metapensiero.sqlalchemy.proxy.utils.SQLALCHEMY_VERSION = (2, 0, 29)

SQLAlchemy version.

metapensiero.sqlalchemy.proxy.utils.col_by_name(query, colname)

Helper: find the (first) column with the given name.

metapensiero.sqlalchemy.proxy.utils.create_change_saver(adaptor=None, save_changes=None, modified_slot_name='modified_records', deleted_slot_name='deleted_records', inserted_ids_slot='inserted_ids', modified_ids_slot='modified_ids', deleted_ids_slot='deleted_ids', result_slot='root', success_slot='success', message_slot='message')

Function factory to implement the standard POST handler for a proxy.

Parameters:

  • adaptor – a function that adapts the changes before application

  • save_changes – the function that concretely applies the changes

  • modified_slot_name – a string, by default ‘modified_records’

  • deleted_slot_name – a string, by default ‘deleted_records’

  • inserted_ids_slot – a string, by default ‘inserted_ids’

  • modified_ids_slot – a string, by default ‘modified_ids’

  • deleted_ids_slot – a string, by default ‘deleted_ids’

  • result_slot – a string, by default ‘root’

  • success_slot – a string, by default ‘success’

  • message_slot – a string, by default ‘message’

Returns:

a dictionary, with a boolean success slot with a True value if the operation was completed without errors, False otherwise: in the latter case the message slot contains the reason for the failure. Three other slots carry lists of dictionaries with the ids of the inserted, modified and deleted records.

This implements the generic behaviour we need to save changes back to the database.

The adaptor function takes four arguments, respectively the SA session, the request, a list of added/modified records and a list of deleted records; it must return two (possibly modified) lists, one containing added/modified records and the other with the records to delete, e.g.:

def adaptor(session, request, modified_recs, deleted_recs):
    # do any step to adapt incoming data
    return modified_recs, deleted_recs
metapensiero.sqlalchemy.proxy.utils.csv_to_list(csv)

Build a list of strings from a CSV or JSON array.

Parameters:

csv – a string containing either a CSV or a JSON array

Return type:

a Python list

This is very simplicistic: since its used to transfer a list of field names, that is plain ASCII strings, JSON escapes are not even considered.

csv may be either a plain CSV string such as first,second,third or a JSON array, such as ["first","second","third"].

metapensiero.sqlalchemy.proxy.utils.get_column_type(column)

Return the concrete type of a column.

metapensiero.sqlalchemy.proxy.utils.get_sqlalchemy_version()

Return the SQLAlchemy version as a tuple of integers.