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Implement simple predicates, including as the only thing in a 'not' clause.

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Richard Newman 2016-07-20 12:21:26 -07:00
parent 345cd9a023
commit cddd72e283
2 changed files with 80 additions and 54 deletions
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106
src/datomish/clauses.cljc
View file

@ -11,13 +11,16 @@
source->constraints]]
[datomish.util :as util #?(:cljs :refer-macros :clj :refer) [raise-str cond-let]]
[datascript.parser :as dp
#?@(:cljs [:refer [Not Pattern DefaultSrc Variable Constant Placeholder]])]
#?@(:cljs
[:refer
[PlainSymbol Predicate Not Pattern DefaultSrc Variable Constant Placeholder]])]
[honeysql.core :as sql]
[clojure.string :as str]
)
#?(:clj
(:import
[datascript.parser Not Pattern DefaultSrc Variable Constant Placeholder])))
[datascript.parser
PlainSymbol Predicate Not Pattern DefaultSrc Variable Constant Placeholder])))
;; A CC is a collection of clauses that are combined with JOIN.
;; The topmost form in a query is a ConjoiningClauses.
@ -41,12 +44,12 @@
;; `from` is a list of [source alias] pairs, suitable for passing to honeysql.
;; `bindings` is a map from var to qualified columns.
;; `wheres` is a list of fragments that can be joined by `:and`.
(defrecord ConjoiningClauses [source from bindings wheres])
(defrecord ConjoiningClauses [source from external-bindings bindings wheres])
(defn bind-column-to-var [cc variable col]
(let [var (:symbol variable)]
(util/conj-in cc [:bindings var] col)))
(defn constrain-column-to-constant [cc col position value]
(util/conj-in cc [:wheres]
[:= col (if (= :a position)
@ -77,7 +80,7 @@
(:wheres cc))))
;; Pattern building is recursive, so we need forward declarations.
(declare Not->NotJoinClause not-join->where-fragment impose-external-bindings)
(declare Not->NotJoinClause not-join->where-fragment)
;; Accumulates a pattern into the CC. Returns a new CC.
(defn apply-pattern-clause
@ -121,41 +124,72 @@
(util/conj-in cc [:from] [table alias])
places)))
(defn- plain-symbol->sql-predicate-symbol [fn]
(when-not (instance? PlainSymbol fn)
(raise-str "Predicate functions must be named by plain symbols." fn))
(#{:> :< :=} (keyword (name (:symbol fn)))))
(defn apply-predicate-clause [cc predicate]
(when-not (instance? Predicate predicate)
(raise-str "Expected to be called with a Predicate instance." predicate))
(let [f (plain-symbol->sql-predicate-symbol (:fn predicate))]
(when-not f
(raise-str "Unknown function " (:fn predicate)))
(let [args (map
(fn [arg]
(condp instance? arg
Placeholder
(raise-str "Can't use a placeholder in a predicate.")
Variable
(let [v (:symbol arg)
internal-bindings (v (:bindings cc))
external-bindings (v (:external-bindings cc))]
(or (first internal-bindings)
(first external-bindings)
(raise-str "No bindings yet for " v)))
Constant
(constant-in-source (:source cc) (:value arg))
(raise-str "Unknown predicate argument " arg)))
(:args predicate))]
(util/conj-in cc [:wheres] (cons f args)))))
(defn apply-not-clause [cc not]
(when-not (instance? Not not)
(raise-str "Expected to be called with a Not instance." not))
(when-not (instance? DefaultSrc (:source not))
(raise-str "Non-default sources are not supported in patterns. Pattern: " not))
(let [not-join-clause (Not->NotJoinClause (:source cc) not)
seen (set (keys (:bindings cc)))
to-unify (set (map :symbol (:unify-vars not-join-clause)))]
;; If our bindings are already available, great -- emit a :wheres
;; fragment, and include the external bindings so that they match up.
;; Otherwise, we need to delay. Right now we're lazy, so we just fail:
;; reorder your query yourself.
(if (clojure.set/subset? to-unify seen)
(util/conj-in cc [:wheres] (not-join->where-fragment
(impose-external-bindings not-join-clause (:bindings cc))))
(raise-str "Haven't seen all the necessary vars for this `not` clause."))))
;; If our bindings are already available, great -- emit a :wheres
;; fragment, and include the external bindings so that they match up.
;; Otherwise, we need to delay. Right now we're lazy, so we just fail:
;; reorder your query yourself.
(util/conj-in cc [:wheres]
(not-join->where-fragment
(Not->NotJoinClause (:source cc) (:bindings cc) not))))
;; We're keeping this simple for now: a straightforward type switch.
(defn apply-clause [cc it]
(if (instance? Not it)
(apply-not-clause cc it)
(apply-pattern-clause cc it)))
(if (instance? Predicate it)
(apply-predicate-clause cc it)
(apply-pattern-clause cc it))))
(defn expand-pattern-clauses
"Reduce a sequence of patterns into a CC."
[cc patterns]
(reduce apply-clause cc patterns))
(defn patterns->cc [source patterns]
(defn patterns->cc [source patterns external-bindings]
(expand-where-from-bindings
(expand-pattern-clauses
(->ConjoiningClauses source [] {} [])
(->ConjoiningClauses source [] (or external-bindings {}) {} [])
patterns)))
(defn cc->partial-subquery
@ -177,24 +211,34 @@
;; that a declared variable list is valid for the clauses given.
(defrecord NotJoinClause [unify-vars cc])
(defn make-not-join-clause [source unify-vars patterns]
(->NotJoinClause unify-vars (patterns->cc source patterns)))
(defn make-not-join-clause [source external-bindings unify-vars patterns]
(->NotJoinClause unify-vars (patterns->cc source patterns external-bindings)))
(defn Not->NotJoinClause [source not]
(defn Not->NotJoinClause [source external-bindings not]
(when-not (instance? DefaultSrc (:source not))
(raise-str "Non-default sources are not supported in patterns. Pattern: "
not))
(make-not-join-clause source (:vars not) (:clauses not)))
(impose-external-bindings
(make-not-join-clause source external-bindings (:vars not) (:clauses not))))
;; This is so we can link the clause to the outside world.
(defn impose-external-constraints [not-join-clause wheres]
(defn impose-external-constraints [not-join-clause wheres]
(util/concat-in not-join-clause [:cc :wheres] wheres))
(defn impose-external-bindings [not-join-clause bindings]
(defn impose-external-bindings [not-join-clause]
(let [ours (:bindings (:cc not-join-clause))
vars (clojure.set/intersection (set (keys bindings)) (set (keys ours)))
pairings (map (fn [v] [:= (first (v bindings)) (first (v ours))]) vars)]
theirs (:external-bindings (:cc not-join-clause))
vars (clojure.set/intersection (set (keys theirs)) (set (keys ours)))
pairings (map (fn [v] [:= (first (v theirs)) (first (v ours))]) vars)]
(impose-external-constraints not-join-clause pairings)))
(defn not-join->where-fragment [not-join]
[:not [:exists (merge {:select [1]} (cc->partial-subquery (:cc not-join)))]])
[:not
(if (empty? (:bindings (:cc not-join)))
;; If the `not` doesn't establish any bindings, it means it only contains
;; expressions that constrain variables established outside itself.
;; We can just return an expression.
(cons :and (:wheres (:cc not-join)))
;; If it does establish bindings, then it has to be a subquery.
[:exists (merge {:select [1]} (cc->partial-subquery (:cc not-join)))])])

28
src/datomish/query.cljc
View file

@ -50,7 +50,7 @@
(validate-in in)
(assoc context
:elements (:elements find)
:cc (clauses/patterns->cc (:default-source context) where))))
:cc (clauses/patterns->cc (:default-source context) where nil))))
(defn find->sql-clause
"Take a parsed `find` expression and turn it into a structured SQL
@ -76,29 +76,11 @@
(dp/parse-query q))
(comment
(def sql-quoting-style nil))
(comment
(def sql-quoting-style nil)
(datomish.query/find->sql-string (datomish.context/->Context (datomish.source/datoms-source nil) nil nil)
(datomish.query/parse
'[:find ?timestampMicros ?page
:in $
:where
'[:find ?timestampMicros ?page :in $ :where
[?page :page/starred true ?t]
[?t :db/txInstant ?timestampMicros]
(not [?page :page/deleted true]) ])))
(comment
(pattern->sql
(first
(:where
(datascript.parser/parse-query
'[:find (max ?timestampMicros) (pull ?page [:page/url :page/title]) ?page
:in $
:where
[?page :page/starred true ?t]
(not-join [?fo]
[(> ?fooo 5)]
[?xpage :page/starred false]
)
[?t :db/txInstant ?timestampMicros]])))
identity))
(not [(> ?t 1000000)]) ]))
)