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Implement all four find specs. Fixes #38. r=nalexander

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This commit is contained in:
Richard Newman 2016-10-06 18:26:40 -07:00
parent e7add97a67
commit e89544beba
6 changed files with 304 additions and 64 deletions
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64
src/common/datomish/db.cljc
View file

@ -800,29 +800,6 @@
:schema entid-schema
})))
;; TODO: factor this into the overall design.
(defn <?run
"Execute the provided query on the provided DB.
Returns a transduced channel of [result err] pairs.
Closes the channel when fully consumed."
[db find options]
(let [unexpected (seq (clojure.set/difference (set (keys options)) #{:limit :order-by :inputs}))]
(when unexpected
(raise "Unexpected options: " unexpected {:bad-options unexpected})))
(let [{:keys [limit order-by inputs]} options
parsed (query/parse find)
context (-> db
query-context
(query/options-into-context limit order-by)
(query/find-into-context parsed))
row-pair-transducer (projection/row-pair-transducer context)
sql (query/context->sql-string context inputs)
chan (chan 50 row-pair-transducer)]
(s/<?all-rows (.-sqlite-connection db) sql chan)
chan))
(defn reduce-error-pair [f [rv re] [v e]]
(if re
[nil re]
@ -830,11 +807,46 @@
[nil e]
[(f rv v) nil])))
(def default-result-buffer-size 50)
(defn <?q
"Execute the provided query on the provided DB.
Returns a transduced pair-chan with one [[results] err] item."
Returns a transduced pair-chan with either:
* One [[results] err] item (for relation and collection find specs), or
* One [value err] item (for tuple and scalar find specs)."
([db find]
(<?q db find {}))
([db find options]
(a/reduce (partial reduce-error-pair conj) [[] nil]
(<?run db find options))))
(let [unexpected (seq (clojure.set/difference (set (keys options)) #{:limit :order-by :inputs}))]
(when unexpected
(raise "Unexpected options: " unexpected {:bad-options unexpected})))
(let [{:keys [limit order-by inputs]} options
parsed (query/parse find)
context (-> db
query-context
(query/options-into-context limit order-by)
(query/find-into-context parsed))
;; We turn each row into either an array of values or an unadorned
;; value. The row-pair-transducer does this work.
;; The only thing to do to handle the full suite of find specs
;; is to decide if we're then returning an array of transduced rows
;; or just the first result.
row-pair-transducer (projection/row-pair-transducer context)
sql (query/context->sql-string context inputs)
first-only (context/scalar-or-tuple-query? context)
buffer-size (if first-only
1
default-result-buffer-size)
chan (chan buffer-size row-pair-transducer)]
;; Fill the channel.
(s/<?all-rows (.-sqlite-connection db) sql chan)
;; If we only want the first result, great!
;; Otherwise, reduce it down.
(if first-only
chan
(a/reduce (partial reduce-error-pair conj) [[] nil]
chan)))))

62
src/common/datomish/query.cljc
View file

@ -15,6 +15,7 @@
BindScalar
Constant
DefaultSrc
FindRel FindColl FindTuple FindScalar
Pattern
Placeholder
SrcVar
@ -29,6 +30,7 @@
BindScalar
Constant
DefaultSrc
FindRel FindColl FindTuple FindScalar
Pattern
Placeholder
SrcVar
@ -63,10 +65,17 @@
(let [inner-projection (projection/sql-projection-for-relation context)
inner
(merge
;; Always SELECT DISTINCT, because Datalog is set-based.
;; If we're finding a collection or relations, we specify
;; SELECT DISTINCT, because Datalog is set-based.
;; If we're only selecting one result — a scalar or a tuple —
;; then we don't bother.
;;
;; TODO: determine from schema analysis whether we can avoid
;; the need to do this.
{:modifiers [:distinct]}
;; the need to do this even in the collection/relation case.
{:modifiers
(if (= 1 (:limit context))
[]
[:distinct])}
(clauses/cc->partial-subquery inner-projection (:cc context)))
limit (:limit context)
@ -134,6 +143,19 @@
(raise "Invalid limit " limit {:limit limit}))
(assoc context :limit limit :order-by-vars order-by))
(defn find-spec->elements [find-spec]
(condp instance? find-spec
FindRel (:elements find-spec)
FindTuple (:elements find-spec)
FindScalar [(:element find-spec)]
FindColl [(:element find-spec)]
(raise "Unable to handle find spec." {:find-spec find-spec})))
(defn find-spec->limit [find-spec]
(when (or (instance? FindScalar find-spec)
(instance? FindTuple find-spec))
1))
(defn find-into-context
"Take a parsed `find` expression and return a fully populated
Context. You'll want this so you can get access to the
@ -142,15 +164,37 @@
(let [{:keys [find in with where]} find] ; Destructure the Datalog query.
(validate-with with)
(validate-in in)
;; A find spec can be:
;;
;; * FindRel containing :elements. Returns an array of arrays.
;; * FindColl containing :element. This is like mapping (fn [row] (aget row 0))
;; over the result set. Returns an array of homogeneous values.
;; * FindScalar containing :element. Returns a single value.
;; * FindTuple containing :elements. This is just like :limit 1
;; on FindColl, returning the first item of the result array. Returns an
;; array of heterogeneous values.
;;
;; The code to handle these is:
;; - Just above, unifying a variable list in find-spec->elements.
;; - In context.cljc, checking whether a single value or collection is returned.
;; - In projection.cljc, transducing according to whether a single column or
;; multiple columns are assembled into the output.
;; - In db.cljc, where we finally take rows and decide what to push into an
;; output channel.
(let [external-bindings (in->bindings in)
elements (:elements find)
elements (find-spec->elements find)
known-types {}
group-by-vars (projection/extract-group-by-vars elements with)]
(assoc context
:elements elements
:group-by-vars group-by-vars
:has-aggregates? (not (nil? group-by-vars))
:cc (clauses/patterns->cc (:default-source context) where known-types external-bindings)))))
(util/assoc-if
(assoc context
:find-spec find
:elements elements
:group-by-vars group-by-vars
:has-aggregates? (not (nil? group-by-vars))
:cc (clauses/patterns->cc (:default-source context) where known-types external-bindings))
:limit (find-spec->limit find)))))
(defn find->sql-clause
"Take a parsed `find` expression and turn it into a structured SQL

18
src/common/datomish/query/context.cljc
View file

@ -4,12 +4,19 @@
;; A context, very simply, holds on to a default source and some knowledge
;; needed for aggregation.
(ns datomish.query.context)
(ns datomish.query.context
(:require
[datascript.parser :as dp
#?@(:cljs [:refer [FindRel FindColl FindTuple FindScalar]])])
#?(:clj
(:import
[datascript.parser FindRel FindColl FindTuple FindScalar])))
(defrecord Context
[
default-source
elements ; The :find list itself.
find-spec ; The parsed find spec. Used to decide how to process rows.
elements ; A list of Element instances, drawn from the :find-spec itself.
has-aggregates?
group-by-vars ; A list of variables from :find and :with, used to generate GROUP BY.
order-by-vars ; A list of projected variables and directions, e.g., [:date :asc], [:_max_timestamp :desc].
@ -17,5 +24,10 @@
cc ; The main conjoining clause.
])
(defn scalar-or-tuple-query? [context]
(when-let [find-spec (:find-spec context)]
(or (instance? FindScalar find-spec)
(instance? FindTuple find-spec))))
(defn make-context [source]
(->Context source nil false nil nil nil nil))
(->Context source nil nil false nil nil nil nil))

55
src/common/datomish/query/projection.cljc
View file

@ -9,10 +9,28 @@
[datomish.sqlite-schema :as ss]
[datomish.util :as util #?(:cljs :refer-macros :clj :refer) [raise raise-str cond-let]]
[datascript.parser :as dp
#?@(:cljs [:refer [Aggregate Pattern DefaultSrc Variable Constant Placeholder PlainSymbol]])]
#?@(:cljs [:refer
[Aggregate
Constant
DefaultSrc
FindRel FindColl FindTuple FindScalar
Pattern
Placeholder
PlainSymbol
Variable
]])]
)
#?(:clj (:import [datascript.parser Aggregate Pattern DefaultSrc Variable Constant Placeholder PlainSymbol]))
)
#?(:clj (:import
[datascript.parser
Aggregate
Constant
DefaultSrc
FindRel FindColl FindTuple FindScalar
Pattern
Placeholder
PlainSymbol
Variable
])))
(defn lookup-variable [cc variable]
(or (-> cc :bindings variable first)
@ -251,18 +269,37 @@
elements))))
(defn row-pair-transducer [context]
(let [{:keys [elements cc]} context
(let [{:keys [find-spec elements cc]} context
{:keys [source known-types extracted-types]} cc
;; We know the projection will fail above if these aren't simple variables or aggregates.
projectors
(make-projectors-for-columns elements known-types extracted-types)]
(make-projectors-for-columns elements known-types extracted-types)
single-column-find-spec?
(or (instance? FindScalar find-spec)
(instance? FindColl find-spec))]
(map
(fn [[row err]]
(if err
[row err]
[(map (fn [projector] (projector row)) projectors) nil])))))
(if single-column-find-spec?
;; We're only grabbing one result from each row.
(let [projector (first projectors)]
(when (second projectors)
(raise "Single-column find spec used, but multiple projectors present."
{:elements elements
:projectors projectors
:find-spec find-spec}))
(fn [[row err]]
(if err
[nil err]
[(projector row) nil])))
;; Otherwise, collect each column into a sequence.
(fn [[row err]]
(if err
[nil err]
[(map (fn [projector] (projector row)) projectors) nil]))))))
(defn extract-group-by-vars
"Take inputs to :find and, if any aggregates exist in `elements`,

140
test/datomish/test/query.cljc
View file

@ -684,3 +684,143 @@
"something")
'[[?save]]]]}
conn)))))
(deftest-db test-find-specs-expansion conn
(let [attrs (<? (<initialize-with-schema conn save-schema))]
;; Relation.
(is (= {:select (list [:fulltext_datoms0.v :title])
:modifiers [:distinct]
:from (list [:fulltext_datoms 'fulltext_datoms0])
:where (list :and [:= :fulltext_datoms0.a (:save/title attrs)])}
(expand [:find '?title
:in '$
:where '[?save :save/title ?title]]
conn)))
;; Tuple. We expect only one result, and indeed we only take one.
;; No need for :distinct in this case!
(is (= {:select (list [:fulltext_datoms0.v :title])
:modifiers []
:limit 1
:from (list [:fulltext_datoms 'fulltext_datoms0])
:where (list :and [:= :fulltext_datoms0.a (:save/title attrs)])}
(expand [:find '[?title]
:in '$
:where '[?save :save/title ?title]]
conn)))
;; Scalar. As with the tuple form, we expect only one result.
(is (= {:select (list [:fulltext_datoms0.v :title])
:modifiers []
:limit 1
:from (list [:fulltext_datoms 'fulltext_datoms0])
:where (list :and [:= :fulltext_datoms0.a (:save/title attrs)])}
(expand [:find '?title '.
:in '$
:where '[?save :save/title ?title]]
conn)))
;; Collection.
(is (= {:select (list [:fulltext_datoms0.v :title])
:modifiers [:distinct]
:from (list [:fulltext_datoms 'fulltext_datoms0])
:where (list :and [:= :fulltext_datoms0.a (:save/title attrs)])}
(expand [:find '[?title ...]
:in '$
:where '[?save :save/title ?title]]
conn)))))
(defn orderless=
"Compare two arrays regardless of order."
[a b]
(= (set a) (set b)))
(deftest-db test-find-specs-empty-results conn
(let [attrs (<? (<initialize-with-schema conn save-schema))]
;; Relation.
(is (= []
(<? (d/<q (d/db conn)
[:find '?title
:in '$
:where '[?save :save/title ?title]]))))
;; Tuple.
(is (nil? (<? (d/<q (d/db conn)
[:find '[?title]
:in '$
:where '[?save :save/title ?title]]))))
;; Scalar.
(is (nil? (<? (d/<q (d/db conn)
[:find '?title '.
:in '$
:where '[?save :save/title ?title]]))))
;; Collection.
(is (= []
(<? (d/<q (d/db conn)
[:find '[?title ...]
:in '$
:where '[?save :save/title ?title]]))))))
(deftest-db test-find-specs-result-shape conn
(let [attrs (<? (<initialize-with-schema conn save-schema))]
;; Add some data.
(<? (d/<transact! conn
[{:db/id (d/id-literal :db.part/user -1)
:save/title "Some page title"}
{:db/id (d/id-literal :db.part/user -2)
:save/title "A different page"}]))
;; Relation.
(is (orderless=
[["A different page"]["Some page title"]]
(<? (d/<q (d/db conn)
[:find '?title
:in '$
:where '[?save :save/title ?title]]
{:order-by [[:title :asc]]}))))
;; Tuple. We expect only one result, and indeed we only take one.
;; No need for :distinct in this case!
(let [result (<? (d/<q (d/db conn)
[:find '[?title]
:in '$
:where '[?save :save/title ?title]]
{:order-by [[:title :asc]]}))]
(is (= ["A different page"] result)))
;; Scalar. As with the tuple form, we expect only one result.
(let [result (<? (d/<q (d/db conn)
[:find '?title '.
:in '$
:where '[?save :save/title ?title]]
{:order-by [[:title :asc]]}))]
(is (= "A different page" result)))
;; Collection.
(is (orderless=
["Some page title" "A different page"]
(<? (d/<q (d/db conn)
[:find '[?title ...]
:in '$
:where '[?save :save/title ?title]]
{:order-by [[:title :desc]]}))))))
(deftest-db test-tuple conn
(let [attrs (<? (<initialize-with-schema conn save-schema))]
(<? (d/<transact! conn
[{:db/id (d/id-literal :db.part/user -1)
:save/title "Some page title"
:save/excerpt "Some page excerpt"}
{:db/id (d/id-literal :db.part/user -2)
:save/title "A different page"
:save/excerpt "A different excerpt"}]))
(let [result (<? (d/<q (d/db conn)
[:find '[?title ?excerpt]
:in '$
:where
'[?save :save/title ?title]
'[?save :save/excerpt ?excerpt]]))]
(is (or (= ["Some page title" "Some page excerpt"] result)
(= ["A different page" "A different excerpt"] result))))))

29
test/datomish/tofinoish_test.cljc
View file

@ -314,17 +314,12 @@
rows)))))
(defn <find-title [db url]
;; Until we support [:find ?title . :in…] we crunch this by hand.
(go-pair
(first
(first
(<?
(d/<q db
'[:find ?title :in $ ?url
:where
[?page :page/url ?url]
[(get-else $ ?page :page/title "") ?title]]
{:inputs {:url url}}))))))
(d/<q db
'[:find ?title . :in $ ?url
:where
[?page :page/url ?url]
[?page :page/title ?title]]
{:inputs {:url url}}))
;; Ensure that we can grow the schema over time.
(deftest-db test-schema-evolution conn
@ -384,7 +379,7 @@
;; Add a page with no title.
(<? (<add-visit conn {:uri "http://notitle.example.org/"
:session session}))
(is (= "" (<? (<find-title (d/db conn) "http://notitle.example.org/"))))
(is (nil? (<? (<find-title (d/db conn) "http://notitle.example.org/"))))
(let [only-one (<? (<visited (d/db conn) {:limit 1}))]
(is (= 1 (count only-one)))
(is (= (select-keys (first only-one)
@ -483,9 +478,9 @@
(let [results
(<?
(d/<q (d/db conn)
{:find '[?save]
:in '[$]
:where [[(list 'fulltext '$ #{:save/title :save/excerpt} "something")
'[[?save]]]]}))]
(is (= (set (map first results))
[:find '[?save ...]
:in '$
:where [(list 'fulltext '$ #{:save/title :save/excerpt} "something")
'[[?save]]]]))]
(is (= (set results)
#{999 998}))))