sqlalchemy.rst

Using OData with SQLAlchemy

Basic Usage

The easiest way to add OData filtering to a SQLAlchemy query is with the shorthand:

SQLAlchemy ORM

from odata_query.sqlalchemy import apply_odata_query

orm_query = select(MyModel)  # This is any form of Query or Selectable.
odata_query = "name eq 'test'"  # This will usually come from a query string parameter.

query = apply_odata_query(orm_query, odata_query)
results = session.execute(query).scalars().all()

SQLAlchemy Core

Attention

Basic support for SQLAlchemy Core is new since version 0.7.0. It currently does not support relationship traversal or any/all yet. Those operations will raise a NotImplementedException.

from odata_query.sqlalchemy import apply_odata_core

core_query = select(MyTable)  # This is any form of Query or Selectable.
odata_query = "name eq 'test'"  # This will usually come from a query string parameter.

query = apply_odata_query(core_query, odata_query)
results = session.execute(query).scalars().all()

Advanced Usage

If you need some more flexibility or advanced features, the implementation of the shorthand is a nice starting point: :pyodata_query.sqlalchemy.shorthand

Let's break it down real quick:

Parsing the OData Query

Optional: Modifying the AST

Building a Query Filter

To get from an AST to something SQLAlchemy can use, you'll need to use the :pyodata_query.sqlalchemy.orm.AstToSqlAlchemyOrmVisitor (ORM mode) or the :pyodata_query.sqlalchemy.core.AstToSqlAlchemyCoreVisitor (Core mode). It needs to know about the 'root model' or table of your query in order to see which fields exists and how objects are related.

SQLAlchemy ORM

from odata_query.sqlalchemy.orm import AstToSqlAlchemyOrmVisitor

visitor = AstToSqlAlchemyOrmVisitor(MyModel)
query_filter = visitor.visit(ast)

SQLAlchemy Core

from odata_query.sqlalchemy.core import AstToSqlAlchemyCoreVisitor

visitor = AstToSqlAlchemyCoreVisitor(MyTable)
query_filter = visitor.visit(ast)

Optional: Joins

Attention

Relationship traversal and automatic joins are not yet supported for SQLAlchemy Core mode.

If your query spans relationships, the AstToSqlAlchemyClauseVisitor will generate join statements. For the query to work, these will need to be applied explicitly:

for j in visitor.join_relationships:
    query = query.join(j)

Running the query

Finally, we're ready to run the query:

query = query.where(query_filter)
results = s.execute(query).scalars().all()