Split out datomish.query.cc so we can implement clause resolution in more than one namespace. r=nalexander
This commit is contained in:
Richard Newman
parent
fc65f268fa
commit
57d8796d07
2 changed files with 155 additions and 121 deletions
143
src/datomish/query/cc.cljc
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143
src/datomish/query/cc.cljc
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;; This Source Code Form is subject to the terms of the Mozilla Public
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;; License, v. 2.0. If a copy of the MPL was not distributed with this
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;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
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(ns datomish.query.cc
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(:require
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[datomish.query.source
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:refer [attribute-in-source
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constant-in-source]]
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[datomish.util :as util #?(:cljs :refer-macros :clj :refer) [raise raise-str cond-let]]
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[datascript.parser :as dp
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#?@(:cljs
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[:refer
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[
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Constant
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Placeholder
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Variable
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]])])
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#?(:clj
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(:import
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[datascript.parser
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Constant
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Placeholder
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Variable
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])))
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;; A ConjoiningClauses (CC) is a collection of clauses that are combined with JOIN.
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;; The topmost form in a query is a ConjoiningClauses.
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;;
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;;---------------------------------------------------------------------------------------
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;; Done:
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;; - Ordinary pattern clauses turn into FROM parts and WHERE parts using :=.
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;; - Predicate clauses turn into the same, but with other functions.
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;; - `not` turns into NOT EXISTS with WHERE clauses inside the subquery to
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;; bind it to the outer variables, or adds simple WHERE clauses to the outer
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;; clause.
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;; - `not-join` is similar, but with explicit binding.
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;;
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;; Not yet done:
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;; - Function clauses with bindings turn into:
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;; * Subqueries. Perhaps less efficient? Certainly clearer.
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;; * Projection expressions, if only used for output.
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;; * Inline expressions?
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;; - `or` turns into a collection of UNIONs inside a subquery.
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;; `or`'s documentation states that all clauses must include the same vars,
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;; but that's an over-simplification: all clauses must refer to the external
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;; unification vars.
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;; The entire UNION-set is JOINed to any surrounding expressions per the `rule-vars`
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;; clause, or the intersection of the vars in the two sides of the JOIN.
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;;---------------------------------------------------------------------------------------
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;;
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;; `from` is a list of [source alias] pairs, suitable for passing to honeysql.
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;; `bindings` is a map from var to qualified columns.
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;; `wheres` is a list of fragments that can be joined by `:and`.
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(defrecord ConjoiningClauses [source from external-bindings bindings wheres])
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(defn bind-column-to-var [cc variable col]
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(let [var (:symbol variable)]
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(util/conj-in cc [:bindings var] col)))
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(defn constrain-column-to-constant [cc col position value]
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(util/conj-in cc [:wheres]
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[:= col (if (= :a position)
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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 augment-cc [cc from bindings wheres]
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(assoc cc
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:from (concat (:from cc) from)
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:bindings (merge-with concat (:bindings cc) bindings)
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:wheres (concat (:wheres cc) wheres)))
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(defn merge-ccs [left right]
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(augment-cc left (:from right) (:bindings right) (:wheres right)))
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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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;; This is so we can link clauses to the outside world.
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(defn- impose-external-bindings [cc]
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(if (empty? (:external-bindings cc))
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cc
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(let [ours (:bindings cc)
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theirs (:external-bindings cc)
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vars (clojure.set/intersection (set (keys theirs)) (set (keys ours)))]
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(util/concat-in
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cc [:wheres]
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(map
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(fn [v]
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(let [external (first (v theirs))
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internal (first (v ours))]
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(assert external)
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(assert internal)
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[:= external internal]))
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vars)))))
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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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(impose-external-bindings
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(assoc cc :wheres
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;; Note that the order of clauses here means that cross-pattern var bindings
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;; come first. That's OK: the SQL engine considers these altogether.
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(concat (bindings->where (:bindings cc))
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(:wheres cc)))))
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(defn binding-for-symbol-or-throw [cc symbol]
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(let [internal-bindings (symbol (:bindings cc))
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external-bindings (symbol (:external-bindings cc))]
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(or (first internal-bindings)
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(first external-bindings)
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(raise-str "No bindings yet for " symbol))))
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(defn argument->value
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"Take a value from an argument list and resolve it against the CC.
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Throws if the value can't be resolved (e.g., no binding is established)."
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[cc arg]
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(condp instance? arg
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Placeholder
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(raise-str "Can't use a placeholder in a predicate.")
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Variable
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(binding-for-symbol-or-throw cc (:symbol arg))
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Constant
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(constant-in-source (:source cc) (:value arg))
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(raise-str "Unknown predicate argument " arg)))
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@ -4,6 +4,7 @@
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(ns datomish.query.clauses
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(:require
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[datomish.query.cc :as cc]
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[datomish.query.source
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:refer [attribute-in-source
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constant-in-source
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@ -43,97 +44,6 @@
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Variable
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])))
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;; A ConjoiningClauses (CC) is a collection of clauses that are combined with JOIN.
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;; The topmost form in a query is a ConjoiningClauses.
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;;
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;;---------------------------------------------------------------------------------------
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;; Done:
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;; - Ordinary pattern clauses turn into FROM parts and WHERE parts using :=.
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;; - Predicate clauses turn into the same, but with other functions.
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;; - `not` turns into NOT EXISTS with WHERE clauses inside the subquery to
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;; bind it to the outer variables, or adds simple WHERE clauses to the outer
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;; clause.
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;; - `not-join` is similar, but with explicit binding.
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;;
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;; Not yet done:
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;; - Function clauses with bindings turn into:
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;; * Subqueries. Perhaps less efficient? Certainly clearer.
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;; * Projection expressions, if only used for output.
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;; * Inline expressions?
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;; - `or` turns into a collection of UNIONs inside a subquery.
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;; `or`'s documentation states that all clauses must include the same vars,
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;; but that's an over-simplification: all clauses must refer to the external
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;; unification vars.
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;; The entire UNION-set is JOINed to any surrounding expressions per the `rule-vars`
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;; clause, or the intersection of the vars in the two sides of the JOIN.
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;;---------------------------------------------------------------------------------------
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;;
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;; `from` is a list of [source alias] pairs, suitable for passing to honeysql.
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;; `bindings` is a map from var to qualified columns.
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;; `wheres` is a list of fragments that can be joined by `:and`.
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(defrecord ConjoiningClauses [source from external-bindings bindings wheres])
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(defn bind-column-to-var [cc variable col]
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(let [var (:symbol variable)]
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(util/conj-in cc [:bindings var] col)))
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(defn constrain-column-to-constant [cc col position value]
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(util/conj-in cc [:wheres]
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[:= col (if (= :a position)
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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 merge-ccs [left right]
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(assoc left
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:from (concat (:from left) (:from right))
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:bindings (merge-with concat (:bindings left) (:bindings right))
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:wheres (concat (:wheres left) (:wheres right))))
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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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;; This is so we can link clauses to the outside world.
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(defn impose-external-bindings [cc]
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(if (empty? (:external-bindings cc))
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cc
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(let [ours (:bindings cc)
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theirs (:external-bindings cc)
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vars (clojure.set/intersection (set (keys theirs)) (set (keys ours)))]
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(util/concat-in
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cc [:wheres]
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(map
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(fn [v]
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(let [external (first (v theirs))
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internal (first (v ours))]
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(assert external)
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(assert internal)
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[:= external internal]))
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vars)))))
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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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(impose-external-bindings
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(assoc cc :wheres
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;; Note that the order of clauses here means that cross-pattern var bindings
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;; come first. That's OK: the SQL engine considers these altogether.
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(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
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Not->NotJoinClause not-join->where-fragment
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@ -159,10 +69,10 @@
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cc
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Variable
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(bind-column-to-var cc pattern-part col)
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(cc/bind-column-to-var cc pattern-part col)
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Constant
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(constrain-column-to-constant cc col position (:value pattern-part))
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(cc/constrain-column-to-constant cc col position (:value pattern-part))
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(raise "Unknown pattern part." {:part pattern-part :clause pattern}))))
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@ -212,26 +122,7 @@
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(when-not f
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(raise-str "Unknown function " (:fn predicate)))
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(let [args (map
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(fn [arg]
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(condp instance? arg
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Placeholder
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(raise-str "Can't use a placeholder in a predicate.")
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Variable
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(let [v (:symbol arg)
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internal-bindings (v (:bindings cc))
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external-bindings (v (:external-bindings cc))]
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(or (first internal-bindings)
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(first external-bindings)
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(raise-str "No bindings yet for " v)))
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Constant
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(constant-in-source (:source cc) (:value arg))
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(raise-str "Unknown predicate argument " arg)))
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(:args predicate))]
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(let [args (map (partial cc/argument->value cc) (:args predicate))]
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(util/conj-in cc [:wheres] (cons f args)))))
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(defn apply-not-clause [cc not]
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@ -270,11 +161,11 @@
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;; subquery.
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(if (simple-or? orc)
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(merge-ccs cc (simple-or->cc (:source cc)
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(merge-with concat
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(:external-bindings cc)
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(:bindings cc))
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orc))
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(cc/merge-ccs cc (simple-or->cc (:source cc)
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(merge-with concat
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(:external-bindings cc)
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(:bindings cc))
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orc))
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;; TODO: handle And within the Or patterns.
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(raise "Non-simple `or` clauses not yet supported." {:clause orc})))
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@ -308,9 +199,9 @@
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(reduce apply-clause cc patterns))
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(defn patterns->cc [source patterns external-bindings]
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(expand-where-from-bindings
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(cc/expand-where-from-bindings
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(expand-pattern-clauses
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(map->ConjoiningClauses
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(cc/map->ConjoiningClauses
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{:source source
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:from []
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:external-bindings (or external-bindings {})
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@ -401,7 +292,7 @@
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;; We 'fork' a CC for each pattern, then union them together.
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;; We need to build the first in order that the others use the same
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;; column names.
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(let [cc (map->ConjoiningClauses
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(let [cc (cc/map->ConjoiningClauses
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{:source source
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:from []
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:external-bindings (or external-bindings {})
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