This project provides DBMS functionalities to Geobricks modules, enabling CRUD methods for different types of DB (e.g. PostgreSQL, MongoDB, etc). The main script is dbms_core.py which acts as a generic gateway to the class that implements specific methods for each data source.

The plug-in is distributed through PyPi and can be installed by typing the following command in the console:

pip install geobricksdbms

The main class is DBMS contained in dbms_core.py. The initialization method of such class accepts the following arguments:

Once initialized the DBMS class provides a set of CRUD methods as discussed in the following sections.

The example below shows how to connect to the test data source and to the posts collection:

my_db = DBMS('mongodb', 'test', collection_name='posts')

Once the connection has been estabilished it is possible to query the DB. The find_all method retrieves all the items of the collection:

for row in my_db.find_all():
    print row

It is also possible to select a single item by ID:

item = my_db.find_by_id('547305f8f8cd671df13e6765')

The insert method allows the user to add new documents in the collection:

new_id = my_db.insert({'my_field': 'my_value'})
print new_id

The example below shows how to connect to the geobricks data source:

my_db = DBMS('postgresql', 'geobricks', 'my_username', 'my_password')

Once the connection has been estabilished it is possible to query the DB. The find_all method retrieves all the items of the collection, and takes the table name as argument:

for row in my_db.find_all('tasks'):
    print row

To insert a new item in the DB you will have to specify the table name and provide a Dict where the keys represents the column names and the values are the values to be stored in the DB. As istance the following code:

my_db.insert({'year': '2014', 'month': '11'}, 'tasks')

add the following record in the tasks table:

Only the fields specified in the Dict have been stored in the tasks table.

It is possible to connect to a default datasource with no need to send the parameters to the init function. This is particularly useful when the DB must be accessed through the REST services and it is not safe, ot at least not recomendable, to embed usernames and/or password in the URL's. Available datasources are stored in a default DB that is configured in the config/dbms_config.py file. The default datasource can be PostgreSQL, MongoDB or any vendor supported by Geobricks DBMS. The following example shows the configuration for a PostgreSQL default DB:

config = {
    "default_datasource": {
        "vendor": "postgresql",
        "db_name": "my_db",
        "table_name": "datasources",
        "username": "my_username",
        "password": "my_password"
    }
}

These are the required field to configure a PostgreSQL default datasource:

Following an example for the configuration of a MongoDB default datasource:

config = {
    "default_datasource": {
        "vendor": "mongodb",
        "db_name": "my_db",
        "collection": "datasources"
    }
}

The following are the required parameters:

The default datasource provides the details for a DB containing all the available datasources. Such datasources are identified by the datasource field. Each datasource must provide the following information:

Please note that the default DB is different from the datasources. It is possible to use a SQL DB as repository for the datasources and have only NoSQL DB's. The datasource field is used to fetch all the required parameters to connect to the specified datasource. The following example show how to list all the items contained in the tasks table by providing the datasource name:

my_db = DBMS(datasource='test_postgresql')
for row in my_db.find_all('tasks'):
    print row

The test_postgresql datasource is stored in the default DB and, in the case of a SQL DB, it is described as follow:

The document for the same datasource in a NoSQL default DB is the following:

{
    "datasource": "test_postgresql",
    "vendor": "postgresql",
    "db_name": "test",
    "username": "postgres",
    "password": "mypassword"
}