Jam.py documentation

Version 5.4.57

Library:

• Record locking bug, when PostgreSQL, MSSQL or Firebird database is used, fixed

To use record locking for items for which you defined on_apply event handler you must change. Add the connection parameter, create a cursor and use the cursor to execute sql queries. Otherwise the record locking won’t work.

For example, the code

def on_apply(item, delta, params):
    tracks_sql = []
    delta.update_deleted()
    for d in delta:
        for t in d.invoice_table:
            if t.rec_inserted():
                sql = "UPDATE DEMO_TRACKS SET TRACKS_SOLD = COALESCE(TRACKS_SOLD, 0) + \
                %s WHERE ID = %s" % \
                (t.quantity.value, t.track.value)
            elif t.rec_deleted():
                sql = "UPDATE DEMO_TRACKS SET TRACKS_SOLD = COALESCE(TRACKS_SOLD, 0) - \
                (SELECT QUANTITY FROM DEMO_INVOICE_TABLE WHERE ID=%s) WHERE ID = %s" % \
                (t.id.value, t.track.value)
            elif t.rec_modified():
                sql = "UPDATE DEMO_TRACKS SET TRACKS_SOLD = COALESCE(TRACKS_SOLD, 0) - \
                (SELECT QUANTITY FROM DEMO_INVOICE_TABLE WHERE ID=%s) + %s WHERE ID = %s" % \
                (t.id.value, t.quantity.value, t.track.value)
            tracks_sql.append(sql)
    sql = delta.apply_sql()
    return item.task.execute(tracks_sql + [sql])

must be changed to

def on_apply(item, delta, params, connection):
    with item.task.lock('invoice_saved'):
        cursor = connection.cursor()
        delta.update_deleted()
        for d in delta:
            for t in d.invoice_table:
                if t.rec_inserted():
                    sql = "UPDATE DEMO_TRACKS SET TRACKS_SOLD = COALESCE(TRACKS_SOLD, 0) + \
                    %s WHERE ID = %s" % \
                    (t.quantity.value, t.track.value)
                elif t.rec_deleted():
                    sql = "UPDATE DEMO_TRACKS SET TRACKS_SOLD = COALESCE(TRACKS_SOLD, 0) - \
                    (SELECT QUANTITY FROM DEMO_INVOICE_TABLE WHERE ID=%s) WHERE ID = %s" % \
                    (t.id.value, t.track.value)
                elif t.rec_modified():
                    sql = "UPDATE DEMO_TRACKS SET TRACKS_SOLD = COALESCE(TRACKS_SOLD, 0) - \
                    (SELECT QUANTITY FROM DEMO_INVOICE_TABLE WHERE ID=%s) + %s WHERE ID = %s" % \
                    (t.id.value, t.quantity.value, t.track.value)
                cursor.execute(sql)