flask-sqlalchemy-qs

flask-sqlalchemy-qs

flask-sqlalchemy-qs is a Python library that enables processing of query strings and its usage in conjunction with Flask and SQLAlchemy. The library provides tools for generating and manipulating SQLAlchemy filters and sorts from query strings in the URL, making it easier to build robust and flexible RESTful APIs.

A User model has a username column attribute to filter:

/users?filters[username][eq]=[e-mail]

A User model has a person relationship attribute, and a list of users has to be filtered and sorted by an attribute of that relationship:

/users?filters[person][age][gte]=22&sorts[0][person][age]=DESC&limit=10&offset=0

Installation

Install flask-sqlalchemy-qs with pip:

pip install flask-sqlalchemy-qs

Usage

To get the filters, sorts, limit, and offset from the query string is necesarry to follow the next syntaxis:

For the "filters" parameter

Filter your list result by column and relationship model properties.

GET /api/endpoint?filters[field][operator]=value

The following operators are available:

Operator	Description
eq	Equal
ne	Not equal
is	Is
is_not	Is not
lt	Less than
lte	Less than or equal to
gt	Greater than
gte	Greater than or equal to
in	Included in an array
nin	Not included in an array
contains	Contains
ncontains	Does not contain
icontains	Contains (case-insensitive)
like	Like
ilike	Like (case-insensitive)
not_like	Not Like
not_ilike	Not Like (case-insensitive)
nicontains	Does not contain (case-insensitive)
startswith	Starts with
istartswith	Starts with (case-insensitive)
endswith	Ends with
iendswith	Ends with (case-insensitive)
or	Joins the filters in an "or" expression
and	Joins the filters in an "and" expression
not	Joins the filters in an "not" expression

Examples:

• Simple usage

/users?filters[username][eq]=[e-mail]

• Relationship usage (User has a person)

/users?filters[person][name][eq]=Marco

• Multiple usage

/users?filters[username][contains]=awesome.com&filters[person][age][gte]=25

• In and nin usage

/users?filters[person][age][in][0]=20&filters[person][age][in][1]=25&filters[person][age][in][2]=30

• Boolean usage

/users?filters[or][0][username][eq]=username1&filters[or][1][username][eq]=username2

• Complex boolean usage

/users?filters[or][0][username][contains]=awesome.com&filters[or][1][not][0][and][0][person][age][gte]=20&filters[or][1][not][0][and][1][person][age][lte]=30

• JSON support followed by dot notation

/users?filters[json_column.foo][eq]=bar

For the "sorts" parameter

Sort your list result by column and relationship model properties.

GET /api/endpoint?sorts[priority_index][field]=order

Examples:

• Single sort usage

/users?sorts[0][username]=DESC

• Multiple order priority and relationship usage

/users?sorts[0][username]=DESC&sorts[1][person][age]=ASC

For the "limit" and "offset" parameter

Limt (amount of elements) and offset (amount of skipped elements) for your list result.

GET /api/endpoint?limit=10&offset=2

Examples:

/users?limit=100&offset=5

Implementation

In order to use it in the sqlalchemy query object. The BaseQuery needs to be imported and set as the query_class in the model

from typing import Dict, List, Tuple, Union
from flask_sqlalchemy_qs import get_url_query_ctx, BaseQuery

...

db = SQLAlchemy(app)

# In this case, a Base Model is defined with its query_class attribute set to BaseQuery
class Base(db.Model):
  __abstract__ = True
  query_class = BaseQuery

class User(Base):
  id       = db.Column(db.Integer, primary_key=True)
  ...

...

#Types
FilterType = Dict[str, Union[bool, str, Dict]]
SortType = Dict[str, Union[str, Dict]]

...

@myblueprint.route('/users', methods=['GET'])
def get_all_users():
  #Get the query string in the correct format
  ctx: Dict[str, Union[FilterType, List[SortType], int]] = get_url_query_ctx()

  filters:FilterType   = ctx["filters"]
  sorts:List[SortType] = ctx["sorts"]
  limit:int            = ctx["limit"]
  offset:int           = ctx["offset"]


  #Query the model with the extended methods
  query = User.query.filter_by_ctx(filters=filters) \
                    .sort_by_ctx(sorts=sorts) \
                    .offset(offset) \
                    .limit(limit)
  
  ...

  results = query.all()

  ...

Version

1.1.5

Requirements

SQLALCHEMYSQLAlchemy~=2.0

flask~=2.2

flask-sqlalchemy~=3.0

Contribution

Contributions to this project are welcome. Please open an issue or make a pull request.

License

This project is licensed under the terms of the MIT license.

Support

If you have any issues or suggestions, please open an issue on this repository.

Authors

Marco Gil, [e-mail]