Geobricks DBMS

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.

Installation

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

pip install geobricksdbms

Examples

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

Name	Description	Default	Example
datasource	Name of a default datasource.	None	my_datasource
vendor	DB connector to use	None	mongodb postgresql
db_name	Name of the DB	None	my_db
username	Username to access the DB	None	my_username
password	Password to access the DB	None	my_password
collection_name	Name of the collection (MongoDB only)	None	my_collection

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

MongoDB

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

PostgreSQL

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:

year	month	day	hour	second
2014	11

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

Connect by datasource name

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:

Field Name	Field Description	Example
vendor	Database vendor	postgresql
db_name	Name of the DB for the connection	my_db
table_name	Name of the table containing the default datasources	datasources
username	Username for the connection	my_username
password	Password for the connection	my_password

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:

Field Name	Field Description	Example
vendor	Database vendor	postgresql
db_name	Name of the DB for the connection	my_db
collection	Name of the table collection containing the default datasources	datasources

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:

Field Name	Field Description	Example	Notes
id	Record ID	123456	SQL only
datasource	Unique identifier	test_db
vendor	DB vendor	postgresql
db_name	Name of the DB for the connection	my_db
username	Username for the connection	my_username	SQL only
password	Password for the connection	my_password	SQL only
collection	Name of the table collection containing thes default datasources	posts	NoSQL only

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:

id	datasource	vendor	db_name	username	password	collection
123456	test_postgresql	postgresql	test	postgres	mypassword	null

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"
}