Categorical Query Language (CQL) implementation in Haskell.
CQL is a functional query language that allows you to specify data migrations declaratively, in a way that guarantees their correctness.
It is the culmination of years of original mathematical research after the right balance between flexibility and correctness. Its solid grounding in category theory sets it apart from its ad hoc counterparts, and enables the compositional development and analysis of data transformations to a degree previously impossible.
CQL, formerly known as AQL, was developed by Statebox in collaboration with Conexus, who develop the Java version of CQL.
After building, you can use cql to evaluate a .cql file, e.g.
# build it
stack build
# run `cql` on `examples/Employee.cql`
stack exec cql examples/Employee.cqlHere is an example of what a .cql file looks like:
options
program_allow_nontermination_unsafe = true
allow_empty_sorts_unsafe = true
typeside T = literal {
types
string
nat
constants
Al Akin Bob Bo Carl Cork Dan Dunn Math CS : string
zero : nat
functions
succ : nat -> nat
plus : nat, nat -> nat
}
schema S = literal : T {
entities
Employee
Department
foreign_keys
manager : Employee -> Employee
worksIn : Employee -> Department
secretary : Department -> Employee
attributes
first last : Employee -> string
age : Employee -> nat
name : Department -> string
}
instance I = literal : S {
generators
a b : Employee
equations
a.manager = a
a.worksIn.secretary = a
b.manager = a
b.worksIn = a.worksIn
last(b) = Bo
multi_equations
first -> {a Al, b Bob}
}
instance J = literal : S {
generators
a b : Employee
c d : Department
y : nat
equations
a.manager = a
a.worksIn = d
c.secretary = b
b.manager = a
b.worksIn = c
d.secretary = b
first(a) = Al
a.last = Al
d.name = Bob
c.name = Al
age(a) = zero
age(b) = y
options interpret_as_algebra = true
}
The package can be built/tested/installed the following ways.
Build:
stack build
Test:
stack test
Install:
stack install
Generate docs:
stack haddock cql
Generate .cabal file:
hpack
Build:
cabal build
Test:
cabal test
Install:
cabal install
Build & test:
nix-build
Install in current profile:
nix-env -f . -i
See also default.nix
To launch the APIs, use stack exec cql-http. Then you can send http requests to port 8080, with an CQL specification in the body. The Content-Type of the request needs to be set to text/plain;charset=utf-8
For example, you could try using cURL as follows
curl -X POST \
http://localhost:8080/cql \
-H 'Content-Type: text/plain;charset=utf-8' \
--data-binary "@./examples/Employee.cql"
You can set the following environment variables to customise the behaviour of the endpoint:
CQL_ENV: Should beDevelopmentorProduction. Regulates the verbosity of the console output.PORT: determines on which port the endpoint is exposed
Unless explicitly stated otherwise all files in this repository are licensed under the GNU Affero General Public License.
Copyright © 2019 Stichting Statebox.