Queries containing 'not' can now be translated to SQL.
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4 changed files with 73 additions and 92 deletions
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@ -53,6 +53,30 @@
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(attribute-in-source (:source cc) value)
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(constant-in-source (:source cc) value))]))
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(defn- bindings->where
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"Take a bindings map like
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{?foo [:datoms12.e :datoms13.v :datoms14.e]}
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and produce a list of constraints expression like
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[[:= :datoms12.e :datoms13.v] [:= :datoms12.e :datoms14.e]]
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TODO: experiment; it might be the case that producing more
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pairwise equalities we get better or worse performance."
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[bindings]
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(mapcat (fn [[_ vs]]
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(when (> (count vs) 1)
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(let [root (first vs)]
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(map (fn [v] [:= root v]) (rest vs)))))
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bindings))
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(defn expand-where-from-bindings
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"Take the bindings in the CC and contribute
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additional where clauses. Calling this more than
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once will result in duplicate clauses."
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[cc]
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(assoc cc :wheres (concat (bindings->where (:bindings cc))
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(:wheres cc))))
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;; Pattern building is recursive, so we need forward declarations.
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(declare Not->NotJoinClause not-join->where-fragment impose-external-bindings)
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;; Accumulates a pattern into the CC. Returns a new CC.
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@ -104,47 +128,25 @@
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(when-not (instance? DefaultSrc (:source not))
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(raise-str "Non-default sources are not supported in patterns. Pattern: " not))
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(let [not-join-clause (Not->NotJoinClause (:source cc) not)]
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(let [not-join-clause (Not->NotJoinClause (:source cc) not)
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seen (set (keys (:bindings cc)))
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to-unify (set (map :symbol (:unify-vars not-join-clause)))]
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;; If our bindings are already available, great -- emit a :wheres
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;; fragment, and include the external bindings so that they match up.
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;; Otherwise, we need to delay, and we do that now by failing.
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(let [seen (set (keys (:bindings cc)))
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to-unify (set (map :symbol (:unify-vars not-join-clause)))]
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(println "Seen " seen " need " to-unify)
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(if (clojure.set/subset? to-unify seen)
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(util/conj-in cc [:wheres] (not-join->where-fragment
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(impose-external-bindings not-join-clause (:bindings cc))))
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(raise-str "Haven't seen all the necessary vars for this `not` clause.")))))
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;; Otherwise, we need to delay. Right now we're lazy, so we just fail:
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;; reorder your query yourself.
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(if (clojure.set/subset? to-unify seen)
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(util/conj-in cc [:wheres] (not-join->where-fragment
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(impose-external-bindings not-join-clause (:bindings cc))))
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(raise-str "Haven't seen all the necessary vars for this `not` clause."))))
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;; We're keeping this simple for now: a straightforward type switch.
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(defn apply-clause [cc it]
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(if (instance? Not it)
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(apply-not-clause cc it)
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(apply-pattern-clause cc it)))
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(defn- bindings->where
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"Take a bindings map like
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{?foo [:datoms12.e :datoms13.v :datoms14.e]}
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and produce a list of constraints expression like
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[[:= :datoms12.e :datoms13.v] [:= :datoms12.e :datoms14.e]]
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TODO: experiment; it might be the case that producing more
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pairwise equalities we get better or worse performance."
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[bindings]
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(mapcat (fn [[_ vs]]
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(when (> (count vs) 1)
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(let [root (first vs)]
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(map (fn [v] [:= root v]) (rest vs)))))
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bindings))
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(defn expand-where-from-bindings
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"Take the bindings in the CC and contribute
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additional where clauses. Calling this more than
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once will result in duplicate clauses."
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[cc]
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(assoc cc :wheres (concat (bindings->where (:bindings cc))
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(:wheres cc))))
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(defn expand-pattern-clauses
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"Reduce a sequence of patterns into a CC."
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[cc patterns]
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@ -156,6 +158,17 @@
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(->ConjoiningClauses source [] {} [])
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patterns)))
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(defn cc->partial-subquery
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"Build part of a honeysql query map from a CC: the `:from` and `:where` parts.
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This allows for reuse both in top-level query generation and also for
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subqueries and NOT EXISTS clauses."
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[cc]
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(merge
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{:from (:from cc)}
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(when-not (empty? (:wheres cc))
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{:where (cons :and (:wheres cc))})))
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;; A `not-join` clause is a filter. It takes bindings from the enclosing query
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;; and runs as a subquery with `NOT EXISTS`.
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;; The only difference between `not` and `not-join` is that `not` computes
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@ -182,12 +195,6 @@
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vars (clojure.set/intersection (set (keys bindings)) (set (keys ours)))
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pairings (map (fn [v] [:= (first (v bindings)) (first (v ours))]) vars)]
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(impose-external-constraints not-join-clause pairings)))
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(defn cc->partial-subquery [cc]
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(merge
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{:from (:from cc)}
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(when-not (empty? (:wheres cc))
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{:where (cons :and (:wheres cc))})))
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(defn not-join->where-fragment [not-join]
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[:not [:exists (merge {:select 1} (cc->partial-subquery (:cc not-join)))]])
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[:not [:exists (merge {:select [1]} (cc->partial-subquery (:cc not-join)))]])
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@ -6,4 +6,4 @@
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;; it'll also do projection and similar transforms.
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(ns datomish.context)
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(defrecord Context [default-source])
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(defrecord Context [default-source elements cc])
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@ -12,12 +12,10 @@
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)
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(defn lookup-variable [cc variable]
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(println "Looking up " variable " in " (:bindings cc))
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(or (-> cc :bindings variable first)
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(raise-str "Couldn't find variable " variable)))
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(defn apply-elements-to-context [context elements]
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(assoc context :elements elements))
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(defn sql-projection
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"Take a `find` clause's `:elements` list and turn it into a SQL
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projection clause, suitable for passing as a `:select` clause to
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@ -43,7 +41,7 @@
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(raise-str "Unable to :find non-variables."))
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(map (fn [elem]
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(let [var (:symbol elem)]
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[(lookup-variable context var) (util/var->sql-var var)]))
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[(lookup-variable (:cc context) var) (util/var->sql-var var)]))
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elements)))
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(defn row-pair-transducer [context projection]
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@ -4,7 +4,10 @@
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(ns datomish.query
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(:require
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[datomish.clauses :as clauses]
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[datomish.context :as context]
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[datomish.util :as util #?(:cljs :refer-macros :clj :refer) [raise-str cond-let]]
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[datomish.projection :as projection]
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[datomish.transforms :as transforms]
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[datascript.parser :as dp
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#?@(:cljs [:refer [Pattern DefaultSrc Variable Constant Placeholder]])]
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@ -20,11 +23,8 @@
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(defn context->sql-clause [context]
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(merge
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{:select (sql-projection context)
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:from (:from context)}
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(if (empty? (:wheres context))
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{}
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{:where (cons :and (:wheres context))})))
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{:select (projection/sql-projection context)}
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(clauses/cc->partial-subquery (:cc context))))
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(defn context->sql-string [context]
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(->
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@ -48,10 +48,9 @@
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(let [{:keys [find in with where]} find] ; Destructure the Datalog query.
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(validate-with with)
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(validate-in in)
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(apply-elements-to-context
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(expand-where-from-bindings
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(expand-patterns-into-context context where)) ; 'where' here is the Datalog :where clause.
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(:elements find))))
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(assoc context
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:elements (:elements find)
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:cc (clauses/patterns->cc (:default-source context) where))))
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(defn find->sql-clause
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"Take a parsed `find` expression and turn it into a structured SQL
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@ -67,9 +66,8 @@
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(defn find->sql-string
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"Take a parsed `find` expression and turn it into SQL."
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[context find]
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(->>
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find
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(find->sql-clause context)
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(->
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(find->sql-clause context find)
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(sql/format :quoting sql-quoting-style)))
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(defn parse
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(dp/parse-query q))
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(comment
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(datomish.query/find->sql-string
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(datomish.query/parse
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'[:find ?page :in $ :where [?page :page/starred true ?t] ])))
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(def sql-quoting-style nil))
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(comment
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(datomish.query/find->prepared-context
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(datomish.query/find->sql-string (datomish.context/->Context (datomish.source/datoms-source nil) nil nil)
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(datomish.query/parse
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'[:find ?timestampMicros ?page
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:in $
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:where
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[?page :page/starred true ?t]
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[?t :db/txInstant ?timestampMicros]])))
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[?t :db/txInstant ?timestampMicros]
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(not [?page :page/deleted true]) ])))
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(comment
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(pattern->sql
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(first
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(:where
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(datascript.parser/parse-query
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'[:find (max ?timestampMicros) (pull ?page [:page/url :page/title]) ?page
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:in $
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:where
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[?page :page/starred true ?t]
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(first
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(:where
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(datascript.parser/parse-query
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'[:find (max ?timestampMicros) (pull ?page [:page/url :page/title]) ?page
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:in $
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:where
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[?page :page/starred true ?t]
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(not-join [?fo]
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[(> ?fooo 5)]
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[?xpage :page/starred false]
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)
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[?t :db/txInstant ?timestampMicros]])))
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identity))
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(cc->partial-subquery
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(require 'datomish.clauses)
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(in-ns 'datomish.clauses)
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(patterns->cc (datomish.source/datoms-source nil)
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(:where
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(datascript.parser/parse-query
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'[:find (max ?timestampMicros) (pull ?page [:page/url :page/title]) ?page
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:in $
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:where
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[?page :page/starred true ?t]
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(not-join [?page]
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[?page :page/starred false]
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)
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[?t :db/txInstant ?timestampMicros]])))
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(Not->NotJoinClause (datomish.source/datoms-source nil)
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#object[datomish.clauses$Not__GT_NotJoinClause 0x6d8aa02d "datomish.clauses$Not__GT_NotJoinClause@6d8aa02d"]
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datomish.clauses=> #datascript.parser.Not{:source #datascript.parser.DefaultSrc{}, :vars [#datascript.parser.Variable{:symbol ?fooo}], :clauses [#datascript.parser.Pattern{:source #datascript.parser.DefaultSrc{}, :pattern [#datascript.parser.Variable{:symbol ?xpage} #datascript.parser.Constant{:value :page/starred} #datascript.parser.Constant{:value false}]}]})
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[?t :db/txInstant ?timestampMicros]])))
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identity))
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