dbj
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Simple embedded in memory json database
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dbj
dbj is a simple embedded in memory json database.
It is easy to use, fast and has a simple query language.
The code is fully documented, tested and beginner friendly.
Only the standard library is used and it works on Python 2.7, Python 3.4+, PyPy 2.7 and PyPy 3.6.
Usage
.. code-block:: python
>>> from dbj import dbj
>>> db = dbj('mydb.json')
>>> # Insert using an auto generated uuid1 key
>>> db.insert({'name': 'John', 'age': 18})
'a71d90ce0c7611e995faf23c91392d78'
>>> # Insert using a supplied key, in this case '[email protected]'
>>> user = {'name': 'Ana Beatriz', 'age': 10}
>>> db.insert(user, '[email protected]')
'[email protected]'
>>> db.insert({'name': 'Bob', 'age': 30})
'cc6ddfe60c7611e995faf23c91392d78'
>>> db.get('a71d90ce0c7611e995faf23c91392d78')
{'name': 'John', 'age': 18}
>>> db.get('[email protected]')
{'name': 'Ana Beatriz', 'age': 10}
>>> db.find('age >= 18')
['a71d90ce0c7611e995faf23c91392d78', 'cc6ddfe60c7611e995faf23c91392d78']
>>> db.find('name == "ana beatriz"')
['[email protected]']
>>> r = db.find('name == "John" or name == "Bob" and age > 10')
>>> db.getmany(r)
[{'name': 'Bob', 'age': 30}, {'name': 'John', 'age': 18}]
>>> # Sort the result by age
>>> r = db.sort(r, 'age')
>>> db.getmany(r)
[{'name': 'John', 'age': 18}, {'name': 'Bob', 'age': 30}]
>>> # Sort can also be used from find directly
>>> r = db.find('age >= 10', sortby='age')
>>> db.getmany(r)
[{'name': 'Ana Beatriz', 'age': 10}, {'name': 'John', 'age': 18}, {'name': 'Bob', 'age': 30}]
>>> # One-liner:
>>> db.getmany(db.find('age >= 10', sortby='age'))
[{'name': 'Ana Beatriz', 'age': 10}, {'name': 'John', 'age': 18}, {'name': 'Bob', 'age': 30}]
>>> db.save()
True
Install
Install using pip::
$ pip install dbj
Examples
Check the available commands_ for a full list of supported methods.
Import the module and create a new database:
.. code-block:: python
>>> from dbj import dbj
>>> db = dbj('mydb.json')
Insert a few documents with auto generated key:
.. code-block:: python
>>> doc = {'name': 'John Doe', 'age': 18}
>>> db.insert(doc)
'7a5ebd420cb211e98a0ff23c91392d78'
>>> docs = [{'name': 'Beatriz', 'age': 30}, {'name': 'Ana', 'age': 10}]
>>> db.insertmany(docs)
2
Insert with a supplied key:
.. code-block:: python
>>> doc = {'name': 'john', 'age': 20, 'country': 'Brasil'}
>>> db.insert(doc, '1')
1
>>> db.insert({'name': 'Bob', 'age': 40}, '2')
2
>>> db.getallkeys()
['7a5ebd420cb211e98a0ff23c91392d78', 'db21baf80cb211e98a0ff23c91392d78', 'db21edde0cb211e98a0ff23c91392d78', '1', '2']
Pop and delete:
.. code-block:: python
>>> db.delete('1')
True
>>> db.poplast()
{'name': 'Bob', 'age': 40}
>>> db.size()
3
>>> db.getallkeys()
['7a5ebd420cb211e98a0ff23c91392d78', 'db21baf80cb211e98a0ff23c91392d78', 'db21edde0cb211e98a0ff23c91392d78']
Updating an existing document:
.. code-block:: python
>>> db.insert({'name': 'Ethan', 'age': 40}, '1000')
'1000'
>>> db.get('1000')
{'name': 'Ethan', 'age': 40}
>>> db.update('1000', {'age': 50})
True
>>> db.get('1000')
{'name': 'Ethan', 'age': 50}
>>> db.update('1000', {'name': 'Ethan Doe', 'gender': 'male'})
True
>>> db.pop('1000')
{'name': 'Ethan Doe', 'age': 50, 'gender': 'male'}
Retrieving some documents:
.. code-block:: python
>>> db.getall()
[{'name': 'John Doe', 'age': 18}, {'name': 'Beatriz', 'age': 30}, {'name': 'Ana', 'age': 10}]
>>> db.getfirst()
{'name': 'John Doe', 'age': 18}
>>> db.getlast()
{'name': 'Ana', 'age': 10}
>>> db.getrandom() # returns a random document
{'name': 'Ana', 'age': 10}
Check for existance:
.. code-block:: python
>>> db.exists('7a5ebd420cb211e98a0ff23c91392d78')
True
Searchin and sorting:
.. code-block:: python
>>> r = db.sort(db.getallkeys(), 'name')
>>> db.getmany(r)
[{'name': 'Ana', 'age': 10}, {'name': 'Beatriz', 'age': 30}, {'name': 'John Doe', 'age': 18}]
>>> r = db.find('name ?= "john"')
>>> db.getmany(r)
[{'name': 'John Doe', 'age': 18}]
>>> query = 'name == "john doe" or name == "ana" and age >= 10'
>>> r = db.find(query)
>>> db.getmany(r)
[{'name': 'John Doe', 'age': 18}, {'name': 'Ana', 'age': 10}]
>>> r = db.find('age < 40', sortby='age')
>>> db.getmany(r)
[{'name': 'Ana', 'age': 10}, {'name': 'John Doe', 'age': 18}, {'name': 'Beatriz', 'age': 30}]
Save the database to disk:
.. code-block:: python
>>> db.save()
True
To save a prettified json, use indent:
.. code-block:: python
>>> db.save(indent=4)
True
Enable auto saving to disk after a insert, update or delete:
.. code-block:: python
>>> db = dbj('mydb.json', autosave=True)
About the simple query language
The query for the find command uses the following pattern:
field operator value and/or field operator value...
Spaces are mandatory and used as a separator by the parser. For example, the following query will not work::
name=="John" and age >=18
A valid example::
name == "John Doe" and age >= 18
Strings must be enclosed by quotes. Quoted text can be searched using double quotes as the string delimiter, like::
name == ""Bob "B" Lee""
Please note that if value is a string, a search for text will be executed (using the string operatos below) and if value is a number, a number comparison search will be used.
The supported string operators are::
'==' -> Exact match. 'John' will not match 'John Doe' but will match 'john'
by default. If case sensitive is desired, just use find with sens=True. See
available commands below for the full find method signature.
'?=' -> Partial match. In this case, 'John' will match 'John Doe'.
'!=' -> Not equal operator.
The numbers comparison operators are::
'==', '!=', '<', '<=', '>', '>='
The supported logical operatos are::
and, or
Important changes
0.1.4:
- The insert() method will raise a TypeError exception if the document dict is not json serializable.
Performance
Since the entire database is an OrderedDict in memory, performance is pretty good. On a cheap single core VM it can handle dozens of thousands operations per second.
A simple benchmark is included to get a roughly estimative of operations per second. Here is the result on a $5 bucks Linode VM running on Python 3.6::
$ python3.6 bench_dbj.py
--------------------------------
Inserting 100000 documents using auto generated uuid1 key...
Done! Time spent: 3.23s
Inserted: 100000
Rate: 30995 ops/s
--------------------------------
Clearing the database...
Done!
--------------------------------
Inserting 100000 documents using a supplied key...
Done! Time spent: 1.26s
Inserted: 100000
Rate: 79587 ops/s
--------------------------------
Retrieving 100000 documents one at a time...
Done! Time spent: 1.61s
Retrieved: 100000
Rate: 62136 ops/s
--------------------------------
Saving database to disk...
Done! Time spent: 1.09s
--------------------------------
Deleting 100000 documents one at a time...
Done! Time spent: 0.22s
Deleted: 100000
Rate: 450764 ops/s
--------------------------------
Removing file...
Done!
Peak memory usage: 57.37 MB
Available commands
insert(document, key=None) -> Create a new document on database. Args: | document (dict): The document to be created. | key (str, optional): The document unique key. Defaults to uuid1. Returns: The document key.
insertmany(documents) -> Insert multiple documents on database. Args: documents (list): List containing the documents to insert. Returns: Number of inserted documents.
save(indent=None) -> Save database to disk. Args: indent (int or str, optional): If provided, save a prettified json with that indent level. 0, negative or "" will only insert newlines. Returns: True if successful.
clear() -> Remove all documents from database. Returns: True if successful.
size() -> Return the database size. Returns: Number of documents on database.
exists(key) -> Check if a document exists on database. Args: key (str): The document key. Returns: True or False if it does not exist.
delete(key) -> Delete a document on database. Args: key (str): The document key. Returns: True or False if it does not exist.
deletemany(keys) -> Delete multiple documents on database. Args: keys (list): List containing the keys of the documents to delete. Returns: Number of deleted documents.
update(key, values) -> Add/update values on a document. Args: | key (str): The document key. | values (dict): The values to be added/updated. Returns: True or False if document does not exist.
updatemany(keys, values) -> Add/update values on multiple documents. Args: | keys (list): List containing the keys of the documents to update. | values (dict): The values to be added/updated. Returns: Number of updated documents.
get(key) -> Get a document on database. Args: key (str): The document key. Returns: The document or False if it does not exist.
getmany(keys) -> Get multiple documents from database. Args: keys (list): List containing the keys of the documents to retrieve. Returns: List of documents.
getall() -> Return a list containing all documents on database. Returns: List with all database documents.
getallkeys() -> Return a list containing all keys on database. Returns: List with all database keys.
getrandom() -> Get a random document on database. Returns: A document or False if database is empty.
getfirst() -> Get the first inserted document on database. Returns: The first inserted document or False if database is empty.
getlast() -> Get the last inserted document on database. Returns: The last inserted document or False if database is empty.
getfirstkey() -> Get the first key on database. Returns: The first key or False if database is empty.
getlastkey() -> Get the last key on database. Returns: The last key or False if database is empty.
pop(key) -> Get the document from database and remove it. Args: key (str): The document key. Returns: The document or False if it does not exist.
popfirst() -> Get the first inserted document on database and remove it. Returns: The first inserted document or False if database is empty.
poplast() -> Get the last inserted document on database and remove it. Returns: The last inserted document or False if database is empty.
sort(keys, field, reverse=False) -> Sort the documents using the field provided. Args: | keys (list): List containing the keys of the documents to sort. | field (str): Field to sort. | reverse (bool, optional): Reverse search. Defaults to False. Returns: Sorted list with the documents keys.
findtext(field, text, exact=False, sens=False, inverse=False, asc=True) -> Simple text search on the provided field. Args: | field (str): The field to search. | text (str): The value to be searched. | exact (bool, optional): Exact text match. Defaults to False. | sens (bool, optional): Case sensitive. Defaults to False. | inverse (bool, optional): Inverse search, return the documents that do not match the search. Defaults to False. | asc (bool, optional): Ascii conversion before matching, this matches text like 'cafe' and 'café'. Defaults to True. Returns: List with the keys of the documents that matched the search.
findnum(expression) -> Simple number comparison search on provided field. Args: | expression (str): The comparison expression to use, e.g., "age >= 18". The pattern is 'field operator number'. Returns: List with the keys of the documents that matched the search.
find(query, sens=False, asc=True, sortby=None, reverse=False) -> Simple query like search. Args: | query (str): The query to use. | sens (bool, optional): Case sensitive. Defaults to False. | asc (bool, optional): Ascii conversion before matching, this matches text like 'cafe' and 'café'. Defaults to True. | sortby (string, optional): Sort using the provided field. | reverse (bool, optional): Reverse sort. Defaults to False. Returns: List with the keys of the documents that matched the search.
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