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(ns example.query
(:use [plasma graph construct]
(require [plasma.query :as q]
[logjam.core :as log]))
(def acme-graph (open-graph "db/example.query"))
(defn make-acme-graph
(-> (nodes [employees :employees
alice {:name :alice :gender :female}
bob {:name :bob :gender :male}
maria {:name :maria :gender :female}
lugano :lugano-office
geneva :geneva-office
zurich :zurich-office
product-alpha {:label :alpha :price 110.00}
product-beta {:label :beta :price 600.00}
comp-1 {:label :component-1 :cost 24.00}
comp-2 {:label :component-2 :cost 8.00}
comp-3 {:label :component-3 :cost 75.00}
comp-4 {:label :component-4 :cost 120.00}
(edges [
; ROOT-ID employees :employees
; employees alice :person
; employees bob :person
; employees maria :person
ROOT-ID lugano :location
ROOT-ID geneva :location
ROOT-ID zurich :location
alice geneva :manages
geneva alice :managed-by
bob zurich :manages
zurich bob :managed-by
maria lugano :manages
lugano maria :managed-by
ROOT-ID product-alpha :product
ROOT-ID product-beta :product
product-alpha lugano :made-in
product-beta lugano :made-in
product-alpha comp-1 :component
product-alpha comp-2 :component
product-beta comp-2 :component
product-beta comp-3 :component
product-beta comp-4 :component
comp-1 zurich :made-in
comp-2 zurich :made-in
comp-3 geneva :made-in
comp-4 geneva :made-in
(defn setup-acme
(graph-apply acme-graph make-acme-graph))
(defn acme
"Define a helper function to query our acme graph."
(graph-apply acme-graph #(q/query q)))
; basic path selection
; - no binding
; - with binding
; - multiple bindings
(defn products-a
"Select all of the products connected to the root node with an edge
labeled :product."
(q/path [:product]))
(defn products
"Select the products exactly as before, but create a path binding variable
that can be referred to later in the query."
(q/path [product [:product]]))
(defn managers
"Select the manager of each location, and create a query binding
to these manager nodes so they can be referred to within the query."
(q/path [manager [:location :managed-by]]))
(defn components
"Select the components that make up ACME products. This example shows how
you can use multi-segment bindings in a path expression."
(q/path [product [:product]
component [product :component]]))
; projection
(defn product-prices
"By default queries only return the node IDs of the result set, so
if you want to get specific properties of a node you need to project
those properties. Note how the query binding variable \"product\" is
quoted, which differentiates it from a normal program variable. This
allows you to mix both run-time program variables and query execution
time query bindings."
(-> (products)
(q/project ['product :label :price])))
(defn with-product-info
"It can be useful to have a projection function like this, which you
can use to wrap queries that you want to project some specific properties."
(-> query
(q/distinct* 'product)
(q/project ['product :label :price])))
;For example:
; (acme (with-product-info (products)))
(defn with-component-info
"It can be useful to have a projection function like this, which you
can use to wrap queries that you want to project some specific properties."
(-> query
(q/distinct* 'component)
(q/project ['component :label :cost])))
;For example:
; (acme (with-component-info (components)))
(defn with-manager-info
(-> query
(q/distinct* 'manager)
(q/project ['manager :name :gender])))
; Could we do something like this?
(comment def product-component-prices
(-> components
(q/expr [total-cost (sum (:price 'component))])
(q/project ['product :label] 'total-cost)))
; where filtering
; - simple property equality
; - with mathematical expression
; - matching interesting graph pattern using multiple bindings
(defn managers-by-gender
"The where form can be used to filter the results based on property
values of bound nodes."
(-> (managers)
(q/where (= gender (:gender 'manager)))))
(defn female-managers
(managers-by-gender :female))
(defn male-managers
(managers-by-gender :male))
(defn profitable-components
"Where forms can be constructed using both arithmetic and boolean
expressions. Here is a function that returns a query which will
return all components that have a marked-up cost greater than
a given threshold."
[markup threshold]
(-> (components)
(q/where (> (* markup (:cost 'component)) threshold))))
; For example:
; (acme (profitable-components 3 100))
; or with the label and price
; (acme (with-component-info (profitable-components 3 100)))
(defn products-with-components-from
"The where expression can pertain to multiple binding points in the query
as well. For example, this function will return all products that
have components which were made in the specified location."
(q/path [location [(components) :made-in]])
(q/where (= loc (:label 'location)))
(q/distinct* 'product)))
; (acme (with-product-info (products-with-components-from :zurich-office)))
; order-by
; - asc
; - desc
(defn components-by-cost
"By default the sort order is ascending."
(-> (components)
(q/order-by 'component :cost)))
; (acme (with-component-info (components-by-cost)))
(defn products-by-price
"But you can specify descending like so."
(-> (products)
(q/order-by 'product :price :desc)))
;(acme (with-product-info (products-by-price)))
(defn most-expensive-product
(-> (products-by-price)
(q/limit 1)))
; limit
; - need offset?
(defn cheapest-component-limit
(-> (components-by-cost)
(q/limit 1)))
;(acme (with-component-info (cheapest-component)))
; choose
(defn n-random-components
(-> (components)
(q/choose n)))
; (acme (with-component-info (n-random-components 2)))
; TODO: Need to determine what some reasonable semantics would be for group-by
; in a path query...
; group-by
(comment defn components-by-location
(-> (q/path [location [(components) :made-in]])
(q/project ['location [:label :as :location]] ['component :label :cost])))
; (q/group-by* 'location :label)))
; count
(defn num-products
(-> (products)
;(acme (num-products))
(defn num-products-with-components-from
(q/count* (products-with-components-from loc)))
;(acme (num-products-with-components-from :zurich-office))
; average
(defn average-product-price
(-> (products)
(q/avg 'product :price)))
;(acme (average-product-price))
; min/max
(defn cheapest-component
(-> (components)
(q/min* 'component :cost)))
;(acme (with-component-info (cheapest-component)))
(defn most-expensive-component
(-> (components)
(q/max* 'component :cost)))
;(acme (with-component-info (most-expensive-component)))