Implement basic fulltext binding.

src/datomish/query/clauses.cljc

@@ -5,6 +5,7 @@
 (ns datomish.query.clauses
   (:require
      [datomish.query.cc :as cc]
+     [datomish.query.functions :as functions]
      [datomish.query.source
       :refer [attribute-in-source
               constant-in-source
@@ -170,8 +171,9 @@
     ;; TODO: handle And within the Or patterns.
     (raise "Non-simple `or` clauses not yet supported." {:clause orc})))
 
-(apply-function-clause [cc function]
-  cc)
+(defn apply-function-clause [cc function]
+  (or (functions/apply-sql-function cc function)
+      (raise "Unknown function expression." {:clause function})))
 
 ;; We're keeping this simple for now: a straightforward type switch.
 (defn apply-clause [cc it]

src/datomish/query/functions.cljc

@@ -0,0 +1,164 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+(ns datomish.query.functions
+  (:require
+     [honeysql.format :as fmt]
+     [datomish.query.cc :as cc]
+     [datomish.query.source :as source]
+     [datomish.util :as util #?(:cljs :refer-macros :clj :refer) [raise raise-str cond-let]]
+     [datascript.parser :as dp
+      #?@(:cljs
+            [:refer
+             [
+              BindColl
+              BindScalar
+              BindTuple
+              BindIgnore
+              Constant
+              Function
+              PlainSymbol
+              SrcVar
+              Variable
+              ]])]
+     [honeysql.core :as sql]
+     [clojure.string :as str]
+     )
+  #?(:clj
+       (:import
+          [datascript.parser
+           BindColl
+           BindScalar
+           BindTuple
+           BindIgnore
+           Constant
+           Function
+           PlainSymbol
+           SrcVar
+           Variable
+           ])))
+
+;; honeysql's MATCH handler doesn't work for sqlite. This does.
+(defmethod fmt/fn-handler "match" [_ col val]
+  (str (fmt/to-sql col) " MATCH " (fmt/to-sql val)))
+
+(defn fulltext-attribute? [source attribute]
+  ;; TODO: schema lookup.
+  true)
+
+(defn- validate-fulltext-clause [cc function]
+  (let [[src attr search] (:args function)]
+    (when-not (and (instance? SrcVar src)
+                   (= "$" (name (:symbol src))))
+      (raise "Non-default sources not supported." {:arg src}))
+    (when-not (instance? Constant attr)
+      (raise "Non-constant fulltext attributes not supported." {:arg attr}))
+
+    (when-not (fulltext-attribute? (:source cc) (:value attr))
+      (raise-str "Attribute " (:value attr) " is not a fulltext-indexed attribute."))
+
+    (when-not (and (instance? BindColl (:binding function))
+                   (instance? BindTuple (:binding (:binding function)))
+                   (every? (fn [s]
+                             (or (instance? BindIgnore s)
+                                 (and (instance? BindScalar s)
+                                      (instance? Variable (:variable s)))))
+                           (:bindings (:binding (:binding function)))))
+      (raise "Unexpected binding value." {:binding (:binding function)}))))
+
+(defn apply-fulltext-clause [cc function]
+  (validate-fulltext-clause cc function)
+
+  ;; A fulltext search string is either a constant string or a variable binding.
+  ;; The search string and the attribute are used to generate a SQL MATCH expression:
+  ;; table MATCH 'search string'
+  ;; This is then joined against an ordinary pattern to yield entity, value, and tx.
+  ;; We do not currently support scoring; the score value will always be 0.
+  (let [[src attr search] (:args function)
+
+        ;; Pull out the symbols for the binding array.
+        [entity value tx score]
+        (map (comp :symbol :variable)     ; This will nil-out placeholders.
+             (get-in function [:binding :binding :bindings]))
+
+        ;; Find the FTS table name and alias. We might have multiple fulltext
+        ;; expressions so we will generate a query like
+        ;;   SELECT ttt.a FROM t1 AS ttt WHERE ttt.t1 MATCH 'string'
+        [fts-table fts-alias] (source/source->fts-from (:source cc))   ; [:t1 :ttt]
+        match-column (sql/qualify fts-alias fts-table)          ; :ttt.t1
+        match-value (cc/argument->value cc search)
+
+        [datom-table datom-alias] (source/source->non-fts-from (:source cc))
+
+        ;; The following will end up being added to the CC.
+        from [[fts-table fts-alias]
+              [datom-table datom-alias]]
+
+        wheres [[:match match-column match-value]      ; The FTS match.
+
+                ;; The FTS rowid to datom correspondence.
+                [:=
+                 (sql/qualify datom-alias :v)
+                 (sql/qualify fts-alias :rowid)]
+
+                ;; The attribute itself must match.
+                [:=
+                 (sql/qualify datom-alias :a)
+                 (source/attribute-in-source (:source cc) (:value attr))]]
+
+        ;; Now compose any bindings for entity, value, tx, and score.
+        ;; TODO: do we need to examine existing bindings to capture
+        ;; wheres for any of these? We shouldn't, because the CC will
+        ;; be internally cross-where'd when everything is done...
+        bindings (into {}
+                       (filter
+                         (comp not nil? first)
+                         [[entity [(sql/qualify datom-alias :e)]]
+                          [value [match-column]]
+                          [tx [(sql/qualify datom-alias :tx)]]
+
+                          ;; Future: use matchinfo to compute a score
+                          ;; if this is a variable rather than a placeholder.
+                          [score [0]]]))]
+
+    (cc/augment-cc cc from bindings wheres)))
+
+(def sql-functions
+  ;; Future: versions of this that uses snippet() or matchinfo().
+  {"fulltext" apply-fulltext-clause})
+
+(defn apply-sql-function
+  "Either returns an application of `function` to `cc`, or nil to
+   encourage you to try a different application."
+  [cc function]
+  (when (and (instance? Function function)
+             (instance? PlainSymbol (:fn function)))
+    (when-let [apply-f (get sql-functions (name (:symbol (:fn function))))]
+      (apply-f cc function))))
+
+;; A fulltext expression parses to:
+;;
+;; Function ( :fn, :args )
+;;
+;; The args begin with a SrcVar, and then are attr and search.
+;;
+;; This binds a relation of [?entity ?value ?tx ?score]:
+;;
+;;   BindColl
+;;     :binding BindTuple
+;;       :bindings [BindScalar...]
+;;
+;; #datascript.parser.Function
+;; {:fn #datascript.parser.PlainSymbol{:symbol fulltext},
+;;  :args [#datascript.parser.SrcVar{:symbol $}
+;;         #datascript.parser.Constant{:value :artist/name}
+;;         #datascript.parser.Variable{:symbol ?search}],
+;;  :binding #datascript.parser.BindColl
+;;           {:binding #datascript.parser.BindTuple
+;;                     {:bindings [
+;;                       #datascript.parser.BindScalar{:variable #datascript.parser.Variable{:symbol ?entity}}
+;;                       #datascript.parser.BindScalar{:variable #datascript.parser.Variable{:symbol ?name}}
+;;                       #datascript.parser.BindScalar{:variable #datascript.parser.Variable{:symbol ?tx}}
+;;                       #datascript.parser.BindScalar{:variable #datascript.parser.Variable{:symbol ?score}}]}}}
+