nosqlapi 1.0.2

nosqlapi is a library for building standard NOSQL python libraries.

nosqlapi

nosqlapi is a library for building standard NOSQL python libraries.

Full documentation: Read the docs

Introduction

This library is defined to encourage similarity between Python modules used to access NOSQL databases. In this way, I hope for consistency that leads to more easily understood modules, code that generally gets more portability across databases and a broader scope of database connectivity from Python.

This document describes the Python NOSQL database API specification.

Module Interface

Constructors

Access to the database is made available through connection objects. The module must provide the following constructor for these:

Connection(parameters...)

Constructor for creating a connection to the database. This object has a connect method that returns a Session object. It takes a number of parameters which are database dependent.

Globals

api_level

String constant stating the supported DB API level.

Currently, only the strings "1.0".

CONNECTION

Connection object global variable.

SESSION

Session object global variable.

Exceptions

Error

Exception that is the base class of all other error exceptions. You can use this to catch all errors with one single except statement.

UnknownError

Exception raised when an unspecified error occurred. It must be a subclass of Error.

ConnectError

Exception raised for errors that are related to the database connection. It must be a subclass of Error.

CloseError

Exception raised for errors that are related to the database close connection. It must be a subclass of Error.

DatabaseError

Exception raised for errors that are related to the database, generally. It must be a subclass of Error.

DatabaseCreationError

Exception raised for errors that are related to the creation of a database. It must be a subclass of DatabaseError.

DatabaseDeletionError

Exception raised for errors that are related to the deletion of a database. It must be a subclass of DatabaseError.

SessionError

Exception raised for errors that are related to the session, generally. It must be a subclass of Error.

SessionInsertingError

Exception raised for errors that are related to the inserting data on a database session. It must be a subclass of SessionError.

SessionUpdatingError

Exception raised for errors that are related to the updating data on a database session. It must be a subclass of SessionError.

SessionDeletingError

Exception raised for errors that are related to the deletion data on a database session. It must be a subclass of SessionError.

SessionClosingError

Exception raised for errors that are related to the closing database session. It must be a subclass of SessionError.

SessionFindingError

Exception raised for errors that are related to the finding data on a database session. It must be a subclass of SessionError.

SessionACLError

Exception raised for errors that are related to the grant or revoke permission on a database. It must be a subclass of SessionError.

SelectorError

Exception raised for errors that are related to the selectors in general. It must be a subclass of Error.

SelectorAttributeError

Exception raised for errors that are related to the selectors attribute. It must be a subclass of SelectorError.

This is the exception inheritance layout:

Exception
|__Error
   |__UnknownError
   |__ConnectError
   |__CloseError
   |__DatabaseError
   |  |__DatabaseCreationError
   |  |__DatabaseDeletionError
   |__SessionError
   |  |__SessionInsertingError
   |  |__SessionUpdatingError
   |  |__SessionDeletingError
   |  |__SessionClosingError
   |  |__SessionFindingError
   |  |__SessionACLError
   |__SelectorError
      |__SelectorAttributeError

Connection Objects

Connection objects should respond to the following methods.

Connection attributes

.connected

This read-only attribute contains a boolean value.

Connection methods

.close(parameters...)

Closing the connection now.

.connect(parameters...)

Connecting to database with the arguments when object has been instantiated and create a Session object to database.

.create_database(parameters...)

Creating a single database with position and keyword arguments.

.has_database(parameters...)

Checking if exists a single database with position and keyword arguments.

.delete_database(parameters...)

Deleting of a single database with position and keyword arguments.

.databases(parameters...)

List all databases.

.show_database(parameters...)

Show an information of a specific database

Session Objects

Session objects should respond to the following methods.

ATTENTION: Session object it will come instantiated if the connection value contains a compliant API Connection object. database value is optional.

Session attributes

.connection

This read-only attribute contains the connection object or other object to serve connection (like sockets).

.description

This read-only attribute contains the session parameters (can be string, list or dictionary).

.item_count

This read-only attribute contains the number of object returned of an operations.

.database

This read-only attribute contains the name of database in current session.

.acl

This read-only attribute contains the Access Control List in the current session.

.indexes

This read-only attribute contains the name of indexes of the current database.

Session methods

.get(parameters...)

Getting one or more data on specific database with position and keyword arguments.

.insert(parameters...)

Inserting one data on specific database with position and keyword arguments.

.insert_many(parameters...)

Inserting one or more data on specific database with position and keyword arguments.

.update(parameters...)

Updating one existing data on specific database with position and keyword arguments.

.update_many(parameters...)

Updating one or more existing data on specific database with position and keyword arguments.

.delete(parameters...)

Deleting one existing data on specific database with position and keyword arguments.

.close(parameters...)

Closing the session and connection now.

.find(parameters...)

Finding data on specific database with string selector or Selector object with position and keyword arguments.

.grant(parameters...)

Granting ACL on specific database with position and keyword arguments.

.revoke(parameters...)

Revoking ACL on specific database with position and keyword arguments.

.new_user(parameters...)

Creating new normal or admin user.

.set_user(parameters...)

Modifying exists user or reset password.

.delete_user(parameters...)

Deleting exists user.

.add_index(parameters...)

Adding a new index to database.

.delete_index(parameters...)

Deleting exists index to database.

.call(batch, parameters...)

Calling a batch object to execute one or more statement.

Selector Objects

Selector objects should respond to the following methods.

Selector attributes

.selector

This read/write attribute represents the selector key/value than you want search.

.fields

This read/write attribute represents the fields key that returned from find operations.

.partition

This read/write attribute represents the name of partition/collection in a database.

.condition

This read/write attribute represents other condition to apply a selectors.

.order

This read/write attribute represents order returned from find operations.

.limit

This read/write attribute represents limit number of objects returned from find operations.

Selector methods

.build(parameters...)

Building a selector string in the dialect of a NOSQL language based on various property of the Selector object.

Response Objects

Response objects should respond to the following attributes.

Response objects is a species of an either-data type, because contains both success and error values

Response attributes

.data

This read-only attribute represents the effective data than returned (Any object).

.code

This read-only attribute represents a number code of error or success in an operation.

.header

This read-only attribute represents a string information (header) of an operation.

.error

This read-only attribute that throw an Exception if it has been set.

.dict

This read-only attribute represents a dictionary transformation of Response object.

Response methods

.throw()

Raise exception stored in error property.

Batch Objects

Batch objects should respond to the following methods.

Batch attributes

.session

This read/write attribute represents a Session object.

.batch

This read/write attribute represents a batch operation.

Batch methods

.execute(parameters...)

Executing a batch operation with position and keyword arguments.

Each database type may contain unique method names for the database type itself. For example, in the abstract class nosqlapi.docdb.DocumentConnection there is the copy_database method which is not present in the other types. These characteristics distinguish the substantial differences between the four databases.

nosqlapi package

The package nosqlapi is a collection of interface and utility class and functions for build your own NOSQL python package.

Test and installation

To test this package.

$ git clone https://github.com/MatteoGuadrini/nosqlapi.git
$ cd nosqlapi
$ python -m unittest discover tests

Instead, to install package.

$ pip install nosqlapi #from pypi

$ git clone https://github.com/MatteoGuadrini/nosqlapi.git #from official repo
$ cd nosqlapi
$ python setup.py install

Type of NoSql Database

NoSql databases are of four types:

• Key/Value database
• Column database
• Document database
• Graph database

For each type of database, nosqlapi offers standard interfaces, in order to unify as much as possible the names of methods and functions.

For an example, just look at the relevant package test files.

Look as each test module has same class and each class has same method name. For instance, look at MyDBSession class as inherit for each nosqlapi type of abstract class:

$ grep "class MyDBSession" tests/*
tests/test_columndb.py:class MyDBSession(nosqlapi.columndb.ColumnSession):
tests/test_docdb.py:class MyDBSession(nosqlapi.docdb.DocSession):
tests/test_graphdb.py:class MyDBSession(nosqlapi.graphdb.GraphSession):
tests/test_kvdb.py:class MyDBSession(nosqlapi.kvdb.KVSession):

Key-Value database

A key–value database, or key–value store, is a data storage paradigm designed for storing, retrieving, and managing associative arrays, and a data structure more commonly known today as a dictionary or hash table. Dictionaries contain a collection of objects, or records, which in turn have many fields within them, each containing data. These records are stored and retrieved using a key that uniquely identifies the record, and is used to find the data within the database.

import nosqlapi.kvdb

# Redis like database
class RedisConnection(nosqlapi.kvdb.KVConnection):...
class RedisSession(nosqlapi.kvdb.KVSession):...
class RedisResponse(nosqlapi.kvdb.KVResponse):...
class RedisBatch(nosqlapi.kvdb.KVBatch):...
class RedisSelector(nosqlapi.kvdb.KVSelector):...

# Use Redis library
conn = RedisConnection(host='server.local', username='admin', password='pass', database='db')
sess = conn.connect()       # return RedisSession object
# Create a new database
conn.create_database('new_db')

# CRUD operation
C = sess.insert('key', 'value')         # Create
R = sess.get('key')                     # Read
U = sess.update('key', 'new_value')     # Update
D = sess.delete('key')                  # Delete

print(R)                                    # {'key': 'value'}
print(type(R))                              # <class 'RedisResponse'>
print(isinstance(R, nosqlapi.Response))     # True

# Extended CRUD operations
sess.insert_many({'key1': 'value1', 'Key2': 'value2'})
sess.update_many({'key1': 'new_value1', 'Key2': 'new_value2'})

# Complex select operation
sel = RedisSelector(selector='key:value id:1 ttl:300', limit=2)
sess.find(sel)

# Batch operations
op = 'SET hello "Hello"\nSET mykey "new"\nGET mykey\nSET anotherkey "will expire in a minute" EX 60'
batch = RedisBatch(batch=op, session=sess)
resp = batch.execute()
print(resp)            # ('OK', 'OK', {'mykey': 'new'}, 'OK')
print(type(resp))      # <class 'RedisResponse'>

Column database

A column-oriented DBMS or columnar DBMS is a database management system (DBMS) that stores data tables by column rather than by row. Practical use of a column store versus a row store differs little in the relational DBMS world. Both columnar and row databases can use traditional database query languages like SQL to load data and perform queries. Both row and columnar databases can become the backbone in a system to serve data for common extract, transform, load (ETL) and data visualization tools. However, by storing data in columns rather than rows, the database can more precisely access the data it needs to answer a query rather than scanning and discarding unwanted data in rows.

import nosqlapi.columndb

# Cassandra like database
class CassandraConnection(nosqlapi.columndb.ColumnConnection):...
class CassandraSession(nosqlapi.columndb.ColumnSession):...
class CassandraResponse(nosqlapi.columndb.ColumnResponse):...
class CassandraBatch(nosqlapi.columndb.ColumnBatch):...
class CassandraSelector(nosqlapi.columndb.ColumnSelector):...

# Use Cassandra library
conn = CassandraConnection(host='server.local', username='admin', password='pass', database='db')
sess = conn.connect()       # return CassandraSession object
# Create a new database
conn.create_database('new_db')

# CRUD operation
C = sess.insert(table='hitchhikers', columns=('id', 'name', 'age'), values=(1, 'Arthur', 42))            # Create
R = sess.get(table='hitchhikers', columns=('id', 'name', 'age'))                                         # Read
U = sess.update(table='hitchhikers', columns=('id', 'name', 'age'), values=(1, 'Arthur', 43))            # Update
D = sess.delete(table='hitchhikers', conditions=["name='Arthur'", 'age=43'])                             # Delete

print(R)                                    # [(1, 'Arthur', 42)]
print(type(R))                              # <class 'CassandraResponse'>
print(isinstance(R, nosqlapi.Response))     # True

# Extended CRUD operations
sess.insert_many(table='hitchhikers', columns=('id', 'name', 'age'), values=[(1, 'Arthur', 42), (2, 'Arthur', 43)])
sess.update_many(table='hitchhikers', columns=('id', 'name', 'age'), values=[(1, 'Arthur', 44), (2, 'Arthur', 45)])

# Complex select operation
sel = CassandraSelector()
# Table
sel.selector = 'hitchhikers'
# Columns
sel.fields = ['id', 'name', 'age']
sess.find(sel)

# Batch operations
op = "BEGIN BATCH\nINSERT INTO hitchhikers (id, name, age)\n VALUES (1, 'Arthur', 42)\nIF NOT EXISTS;\nAPPLY BATCH;"
batch = CassandraBatch(batch=op, session=sess)
resp = batch.execute()
print(resp)            # [(1, 'Arthur', 42)]
print(type(resp))      # <class 'CassandraResponse'>

Document database

A document-oriented database, or document store, is a computer program and data storage system designed for storing, retrieving and managing document-oriented information, also known as semi-structured data.

Document-oriented databases are one of the main categories of NoSQL databases, and the popularity of the term "document-oriented database" has grown with the use of the term NoSQL itself. Graph databases are similar, but add another layer, the relationship, which allows them to link documents for rapid traversal.

import nosqlapi.docdb

# MongoDB like database
class MongoConnection(nosqlapi.docdb.DocConnection):...
class MongoSession(nosqlapi.docdb.DocSession):...
class MongoResponse(nosqlapi.docdb.DocResponse):...
class MongoBatch(nosqlapi.docdb.DocBatch):...
class MongoSelector(nosqlapi.docdb.DocSelector):...

# Use MongoDB library
conn = MongoConnection(host='server.local', username='admin', password='pass')
sess = conn.connect()       # return MongoSession object
# Create a new database
conn.create_database('new_db')

# CRUD operation
C = sess.insert(path='db/doc1', doc={"_id": "5099803df3f4948bd2f98391", "name": "Arthur", "age": 42})           # Create
R = sess.get(path='db/doc1')                                                                                    # Read
U = sess.update(path='db/doc1', doc={"_id": "5099803df3f4948bd2f98391", "name": "Arthur", "age": 43}, rev=2)    # Update
D = sess.delete(path='db/doc1', rev=2)                                                                          # Delete

print(R)                                    # {"_id": "5099803df3f4948bd2f98391", "rev"= 2, "name": "Arthur", "age": 42}
print(type(R))                              # <class 'MongoResponse'>
print(isinstance(R, nosqlapi.Response))     # True

# Extended CRUD operations
sess.insert_many(database='db', docs=[{"_id": "5099803df3f4948bd2f98391", "name": "Arthur", "age": 42}, 
                 {"_id": "5099803df3f4948bd2f98392", "name": "Arthur", "age": 43}])
sess.update_many(database='db', docs=[{"_id": "5099803df3f4948bd2f98391", "name": "Arthur", "age": 42, "rev": 2}, 
                 {"_id": "5099803df3f4948bd2f98392", "name": "Arthur", "age": 43, "rev": 2}])

# Complex select operation
sel = MongoSelector(selector={"name": "Arthur"}, fields=['_id', 'name', 'age'], limit=2)
sess.find(sel)

# Batch operations
op = [{"_id": "5099803df3f4948bd2f98391", "name": "Arthur", "age": 42}, {"_id": "5099803df3f4948bd2f98392", "name": "Arthur", "age": 43}]
batch = MongoBatch(batch=op, session=sess)
resp = batch.execute(crud='insert')
print(resp)            # [{"_id": "5099803df3f4948bd2f98391", "rev"= 2, "name": "Arthur", "age": 42}, {"_id": "5099803df3f4948bd2f98392", "rev"= 2, "name": "Arthur", "age": 43}]
print(type(resp))      # <class 'MongoResponse'>

Graph database

Graph databases are a type of NoSQL database, created to address the limitations of relational databases. While the graph model explicitly lays out the dependencies between nodes of data, the relational model and other NoSQL database models link the data by implicit connections. In other words, relationships are a first-class citizen in a graph database and can be labelled, directed, and given properties. This is compared to relational approaches where these relationships are implied and must be reified at run-time. Graph databases are similar to 1970s network model databases in that both represent general graphs, but network-model databases operate at a lower level of abstraction and lack easy traversal over a chain of edges.

import nosqlapi.graphdb

# Neo4j like database
class Neo4jConnection(nosqlapi.graphdb.GraphConnection):...
class Neo4jSession(nosqlapi.graphdb.GraphSession):...
class Neo4jResponse(nosqlapi.graphdb.GraphResponse):...
class Neo4jBatch(nosqlapi.graphdb.GraphBatch):...
class Neo4jSelector(nosqlapi.graphdb.GraphSelector):...

# Use Neo4j library
conn = Neo4jConnection(host='server.local', username='admin', password='pass', database='db')
sess = conn.connect()       # return Neo4jSession object
# Create a new database
conn.create_database('new_db')

# CRUD operation
C = sess.insert(node='n:Person', properties={'name': 'Arthur', 'age': 42})           # Create
R = sess.get(node='n:Person')                                                        # Read
U = sess.update(node='n:Person', properties={'name': 'Arthur', 'age': 42})           # Update
D = sess.delete(node='n:Person')                                                     # Delete

print(R)                                    # {'n.name': 'Arthur', 'n.age': 42}
print(type(R))                              # <class 'Neo4jResponse'>
print(isinstance(R, nosqlapi.Response))     # True

# Extended CRUD operations
sess.insert_many(nodes=['matteo:Person', 'arthur:Person'], properties=[{'name': 'Matteo', 'age': 35}, 
                                                                       {'name': 'Arthur', 'age': 42}])
sess.update_many(nodes=['matteo:Person', 'arthur:Person'], properties=[{'name': 'Matteo', 'age': 35}, 
                                                                       {'name': 'Arthur', 'age': 42}])
sess.link(node='arthur:Person{name: "Arthur"}', to_link='book:hitchhikers', relationship=':ACT_IN')
sess.detach(node='arthur:Person{name: "Arthur"}')

# Complex select operation
sel = Neo4jSelector(selector='people:Person', fields=['name', 'age'], condition='people.age>=35', order='age', limit=2)
sess.find(sel)

# Batch operations
op = "MATCH (p:Person {name: 'Arhur'})-[rel:ACT_IN]-(:Book {name: 'hitchhikers'})\nSET rel.startYear = date({year: 2018})\nRETURN p"
batch = Neo4jBatch(batch=op, session=sess)
resp = batch.execute()
print(resp)            # {'p.name': 'Arhur', 'p.age': 42}
print(type(resp))      # <class 'Neo4jResponse'>

ODM (Object-Data Mapping)

For each type of NOSQL database there is an ODM (Object-relational mapping) module that contains classes and functions relating to the mapping of objects and/or operations concerning the specific database CRUD operation.

In the nosqlapi.common.odm module there are also classes that represent the data types of databases.

>>> import nosqlapi.common.odm
>>> [t for t in dir(nosqlapi.common.odm) if not t.startswith('__')]
['Array', 'Ascii', 'Blob', 'Boolean', 'Counter', 'Date', 'Dc', 'Decimal', 'Double', 'Duration', 'Float', 'Inet', 'Int', 
'List', 'Map', 'Null', 'SmallInt', 'Text', 'Time', 'Timestamp', 'Uuid', 'Varchar']

Utilities

The package also comes with useful classes and functions to help migrate a library to these APIs. Besides, these there are also some utilities for end users.

api decorator

import nosqlapi
from pymongo import Connection

# This decorator allows you to map existing method names to API compliant methods.
@nosqlapi.api(database_names='databases', drop_database='delete_database', close_cursor='close')
class ApiConnection(Connection):
    pass

conn = ApiConnection('localhost', 27017, 'test_database')
hasattr(conn, 'databases')      # True
conn.databases()                # (test_database, 'db1', 'db2')

Manager session

import nosqlapi
from neo4j import Neo4jConnection
from mymongo import MongoConnection

# Create manager for session API
man = nosqlapi.Manager(Neo4jConnection(host='server.local', username='admin', password='pass', database='db'))
print(type(man))        # <class 'Manager'>
print(man)              # database=db, description=('db', 'online')

# CRUD operation
C = man.insert(node='n:Person', properties={'name': 'Arthur', 'age': 42})           # Create
R = man.get(node='n:Person')                                                        # Read
U = man.update(node='n:Person', properties={'name': 'Arthur', 'age': 42})           # Update
D = man.delete(node='n:Person')                                                     # Delete

# Change session
man.change(MongoConnection(host='server.local', username='admin', password='pass', database='db'))
C = man.insert(path='db/doc1', doc={"_id": "5099803df3f4948bd2f98391", "name": "Arthur", "age": 42})           # Create
R = man.get(path='db/doc1')                                                                                    # Read
U = man.update(path='db/doc1', doc={"_id": "5099803df3f4948bd2f98391", "name": "Arthur", "age": 43}, rev=2)    # Update
D = man.delete(path='db/doc1', rev=2)                                                                          # Delete

Open source

nosqlapi is an open source project. Any contribute, It's welcome.

A great thanks.

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Acknowledgments

Thanks to Mark Lutz for writing the Learning Python and Programming Python books that make up my python foundation.

Thanks to Kenneth Reitz and Tanya Schlusser for writing the The Hitchhiker’s Guide to Python books.

Thanks to Dane Hillard for writing the Practices of the Python Pro books.

Special thanks go to my wife, who understood the hours of absence for this development. Thanks to my children, for the daily inspiration they give me and to make me realize, that life must be simple.

Thanks Python!