PullQL

A GraphQL-like query language for DataScript, optimized for execution across many entities at once. For such use cases, it is between one and two orders of magnitude faster than d/pull-many. PullQL should work on Datomic databases as well.

Features

• [x] Basic pull-all queries
• [x] Multiple top-level queries via aliases
• [x] Filter clauses on both root entities and children
• [x] Derived attributes
• [x] cljc (usable on back- and frontend)

A previous iteration of this language is described in detail in [0].

(require '[pullql.core :refer [pull-all]])

;; simplest possible pull query
(pull-all db '[:constellation/name])

;; recursively querying relations
(pull-all db '[:constellation/name
               {:constellation/scenario [:scenario/name]}])
			   
;; multiple top-level queries via aliasing
(pull-all db '{:structure [:constellation/name 
                           {:constellation/scenario [:scenario/name]}]
               :detail    [[:scenario/name "Testszenario"]
			               {:scenario/discourse [:discourse/name :discourse/niveau]}]})
               
;; additionally, PullQL supports filters
(pull-all db '[[:constellation/name "Fachstationen"]
               {:constellation/scenario [:scenario/name]}])
               
;; filters can appear in nested clauses as well
(pull-all db '[:constellation/name
               {:constellation/scenario [:scenario/name
                                         {:scenario/discourse [:discourse/name
	                                                      [:discourse/niveau 1]]}]}])
															   
;; filters support a wildcard '_', expressing a required attribute
(pull-all db '[[:constellation/name _]
               {:constellation/scenario [:scenario/name]}])

(pull-all db '[:constellation/name
               {:constellation/scenario [:scenario/name
                                         {:scenario/discourse [:discourse/name
						              [:discourse/niveau _]]}]}])

Derived Attributes

Derived attributes can be thought of as relations between entities and values whose datoms are computed on the fly, rather than being stored permanently. A similar implementation is explained in [1].

Derived attributes must be annotated as :db/valueType :db.type/derived in the schema. Definitions for all derived attributes are specified via a function:

@TODO

Sources

• [0][https://www.nikolasgoebel.com/2018/06/26/a-query-language.html]
• [1][http://www.nikolasgoebel.com/2018/03/25/derived-attributes-datascript.html]