fastapi-query-filters 0.1.0b1

Dynamic and declarative query filters for FastAPI, powered by Pydantic v2 and ready for multiple ORMs.

:rocket: fastapi-query-filters

Dynamic and declarative query filters for FastAPI, powered by Pydantic v2 and ready for multiple ORMs.

Features

• 🔍 Dynamic Filtering: Generate powerful query filters from Pydantic models automatically
• 🎯 Declarative API: Clean, intuitive syntax for defining filters
• 🔌 Multi-ORM Support: Built-in support for SQLAlchemy with extensibility for other ORMs
• 📦 Pydantic v2: Full integration with Pydantic v2 for robust data validation
• ⚡ FastAPI Native: Seamlessly integrates with FastAPI dependencies
• 🔤 Search & Sort: Support for text search and custom sorting operators
• 🌳 Multi-level Relationships: Filter through nested models at any depth
• 🛡️ Strict Mode: Optional strict validation for unknown query parameters
• 🧪 Type Safe: Full type hints and mypy strict mode support

Installation

# Standard installation
pip install fastapi-query-filters

# Installation with SQLAlchemy support
pip install "fastapi-query-filters[sqlalchemy]"

Note: If you are installing directly from GitHub:

pip install "fastapi-query-filters[sqlalchemy] @ git+https://github.com/ezeparziale/fastapi-query-filters.git"

Requirements

• Python >= 3.11
• FastAPI >= 0.110.0
• Pydantic >= 2.0.0
• SQLAlchemy >= 2.0.0

Quick Start

1. Define Your Schema

from datetime import datetime
from pydantic import BaseModel, ConfigDict, EmailStr, Field

class UserOut(BaseModel):
    id: int = Field(json_schema_extra={"filters": ["eq"]})
    email: EmailStr = Field(json_schema_extra={"filters": ["eq", "icontains"]})
    profile_bio: str | None = Field(
        None,
        json_schema_extra={"filters": ["eq", "icontains", "isnull"]},
    )

    model_config = ConfigDict(from_attributes=True)

class PostOut(BaseModel):
    id: int = Field(json_schema_extra={"filters": ["eq", "gte", "lte", "in"]})
    title: str = Field(json_schema_extra={"filters": ["eq", "icontains"]})
    created_at: datetime = Field(json_schema_extra={"filters": ["gte", "lte"]})
    is_active: bool = Field(json_schema_extra={"filters": ["eq"]})
    user_id: int = Field(json_schema_extra={"filters": ["eq"]})
    author: UserOut

    model_config = ConfigDict(from_attributes=True)

    class FilterConfig:
        search_field = "q"
        sort_field = "sort_by"
        enable_sort = True
        enable_search = True
        prefix = ""
        search_columns = ["title", "description"]
        sort_columns = ["id", "title", "created_at", "author__name"]  # Optional whitelist

2. Use in Your Endpoint

from fastapi import Depends, FastAPI
from fastapi_query_filters import FilterDep, FilterValues
from fastapi_query_filters.orm.sqlalchemy import apply_filters

app = FastAPI()

@app.get("/posts")
def list_posts(
    db: Session = Depends(get_db),
    filters: FilterValues = FilterDep(PostOut)
):
    stmt = select(Post)
    stmt = apply_filters(stmt, Post, filters)
    return db.execute(stmt).scalars().all()

3. Query Your API

# Filter by field with eq operator
GET /posts?id__eq=1

# Multiple values for in operator
GET /posts?id__in=1&id__in=2&id__in=3

# Use in operator with comma-separated values
GET /posts?id__in=1,2,3

# Filter by field with icontains operator
GET /posts?title__icontains=python

# Filter by author profile bio NULL / NOT NULL values
GET /posts?author__profile_bio__isnull=true
GET /posts?author__profile_bio__isnull=false

# Multiple filters
GET /posts?published__eq=true&title__icontains=api

# Search across fields
GET /posts?q=fastapi

# Sort results
GET /posts?sort_by=-created_at,title

# Combine filters and search
GET /posts?id__in=1,2,3&is_active__eq=true&q=fastapi&sort_by=-created_at

Supported Operators

The library supports the following filter operators for different field types:

Operator	Description	Example	Types
eq	Equal	id__eq=1	all
ne	Not equal	status__ne=inactive	all
gt	Greater than	age__gt=18	int, datetime
lt	Less than	age__lt=65	int, datetime
gte	Greater than or equal	created_at__gte=2024-01-01	int, datetime
lte	Less than or equal	price__lte=100	int, datetime
in	In list	id__in=1,2,3	all
not_in	Not in list	status__not_in=deleted,archived	all
like	SQL LIKE pattern	name__like=%john%	str
ilike	SQL ILIKE (case-insensitive)	email__ilike=%gmail%	str
icontains	Case-insensitive contains	title__icontains=python	str
isnull	Check if value is NULL or NOT NULL (supports boolean-like values: true/false, yes/no, 1/0, etc.)	status__isnull=true	all

FilterConfig Configuration

Customize filter behavior using the FilterConfig nested class in your schema:

class PostOut(BaseModel):
    # ... fields ...

    class FilterConfig:
        # Query parameter name for global search (default: "q")
        search_field = "q"

        # Query parameter name for sorting (default: "sort_by")
        sort_field = "sort_by"

        # Global prefix for all filter parameters (default: "")
        prefix = ""

        # Enable/disable global search functionality (default: True)
        enable_search = True

        # Enable/disable sorting functionality (default: True)
        enable_sort = True

        # Columns to search when using global search query
        search_columns = ["title", "description", "content"]

        # Maximum depth for recursive relationship filtering (default: 1)
        max_depth = 1

        # Whether to forbid all unknown query parameters (default: False)
        strict = False

        # Optional: explicit whitelist of fields allowed for sorting (default: None = all fields)
        sort_columns = ["id", "title", "created_at", "author__name"]

        # Optional: Pydantic model with virtual/extra filter fields
        extra_filters = PostFilterExtra

FilterConfig Parameters Explained

• search_field: The query parameter name used for global search across multiple columns
• sort_field: The query parameter name used to specify sorting order
• prefix: A prefix prepended to all filter parameter names (e.g., f_id__eq=1)
• enable_search: Toggle global search functionality on/off
• enable_sort: Toggle dynamic sorting functionality on/off
• search_columns: List of database columns to search when using the search_field parameter
• max_depth: Set the recursion limit for relationship filtering. Increase this to allow filtering by fields in nested models (e.g., author__team__name__eq).
• strict: Enable total strict mode to reject any query parameter not defined in the filter model (returns 422 error). In strict mode, this also applies to sort_by — any field not in sort_columns returns 422.
• sort_columns: Explicit list of field names allowed as sort targets. When set, only listed fields can be used with sort_by. If None, all leaf fields from the schema are valid sort targets. In strict mode, passing an unlisted field returns a 422 error; otherwise it is silently ignored.
• extra_filters: A Pydantic model containing additional filter fields from the database that are not included in the main schema output

Advanced Features

Nested Relationship Filtering

Filter by nested relationship fields using double underscore notation:

# Filter posts by author's email
GET /posts?author__email__icontains=example.com

# Filter posts by author's age range
GET /posts?author__age__gte=18&author__age__lte=65

Multi-level Relationships 🌳

Use max_depth to control how deep the relationships can go (default is 1):

class PostOut(BaseModel):
    author: UserOut # UserOut has a 'team' relationship

    class FilterConfig:
        max_depth = 2 # Allow Post -> User -> Team

# Filter posts by author's team name
GET /posts?author__team__name__eq=Medical

Strict Validation Mode 🛡️

By default, unknown query parameters are ignored. Enable strict mode to reject malformed requests or unauthorized parameters:

class FilterConfig:
    strict = True
    prefix = "f_"

# These will return 422 Unprocessable Entity:
GET /posts?invalid_param=1
GET /posts?f_typo__eq=value
GET /posts?page=1 # Even unrelated params are blocked in total strict mode

Strict mode also validates the sort_by parameter when sort_columns is defined. Any sort field not in the whitelist returns 422:

class FilterConfig:
    strict = True
    sort_columns = ["id", "created_at"]

# 422 — not in sort_columns
GET /posts?sort_by=title
GET /posts?sort_by=author__team__name

Dynamic Sorting

Sort by multiple fields with ascending/descending order:

# Sort by created_at (descending), then by title (ascending)
GET /posts?sort_by=-created_at,title

# Sort by multiple fields
GET /posts?sort_by=-updated_at,id,name

By default, all schema leaf fields (including nested ones) are valid sort targets. Use sort_columns to restrict which fields can be sorted:

class PostOut(BaseModel):
    id: int
    title: str
    created_at: datetime
    author: UserOut  # UserOut has 'name', 'team', etc.

    class FilterConfig:
        sort_field = "sort_by"
        sort_columns = ["id", "created_at", "author__name"]  # Only these are sortable

# Allowed
GET /posts?sort_by=id
GET /posts?sort_by=-created_at,author__name

# Silently ignored (strict=False, the default)
GET /posts?sort_by=title

# Returns 422 if strict=True
GET /posts?sort_by=title
GET /posts?sort_by=author__team__name

When strict = True, any sort_by value not present in sort_columns returns a 422 Unprocessable Entity:

class FilterConfig:
    strict = True
    sort_columns = ["id", "created_at"]

# 422 — 'title' is not in sort_columns
GET /posts?sort_by=title

# 422 — '-title' strips the '-' direction prefix, then validates 'title'
GET /posts?sort_by=-title

# 422 — 'id' is valid but 'title' is not, whole request is rejected
GET /posts?sort_by=id,title

Field Aliases

Use filter_alias in json_schema_extra to map query parameters to different field names:

class PostOut(BaseModel):
    title: str = Field(
        alias="post_title",
        json_schema_extra={
            "filters": ["eq", "icontains"],
            "filter_alias": "post_title",
        },
    )

# Query using the alias
GET /posts?post_title__icontains=python

Multiple Query Parameter Values

Multiple values can be passed in different ways:

# Multiple eq operators
GET /posts?id__eq=1&id__eq=2&id__eq=3

# Comma-separated values with in operator
GET /posts?id__in=1,2,3

# Combined search and filters
GET /posts?q=fastapi&is_active__eq=true&author__id__in=1,2,3

Global Prefix

Add a global prefix to all filter parameters for namespace isolation:

class FilterConfig:
    prefix = "f_"

# Query with prefix
GET /posts?f_id__eq=1&f_title__icontains=api

Extra Filters (Virtual Fields)

Define additional filter fields that exist in the database but are not included in your main response schema:

class PostFilterExtra(BaseModel):
    # Database column available for filtering but not in PostOut response
    author__age: int | None = Field(
        default=None,
        json_schema_extra={"filters": ["gte", "lte", "in"]}
    )
    # Another database field not exposed in the API response
    status: str | None = Field(
        default=None,
        json_schema_extra={"filters": ["eq", "in"]}
    )

class PostOut(BaseModel):
    # ... fields exposed in response ...

    class FilterConfig:
        extra_filters = PostFilterExtra

# Query using extra filter fields
GET /posts?author__age__gte=18
GET /posts?status__eq=draft

Documentation

For detailed documentation and examples, see the examples/ directory.

License

MIT License - see LICENSE file for details.

Author

Ezequiel Parziale