next-jdbc/src/next/jdbc.clj

;; copyright (c) 2018-2019 Sean Corfield, all rights reserved

(ns next.jdbc
  ""
  (:require [clojure.set :as set])
  (:import (java.lang AutoCloseable)
           (java.sql Connection DriverManager
                     PreparedStatement
                     ResultSet ResultSetMetaData
                     SQLException Statement)
           (javax.sql DataSource)
           (java.util Properties)))

(comment
  "Key areas of interaction:
  1a. Making a DataSource -- turn everything connectable into a DataSource
  1b. Given a DataSource, we can getConnection()
  2. Preparing a Statement -- connection + SQL + params (+ options)
      (multiple param groups means addBatch() calls)
  3. Execute a (Prepared) Statement to produce a ResultSet (or update count)
      (can execute batch of prepared statements and get multiple results)"

  "Additional areas:
  1. with-db-connection -- given 'something', get a connection, execute the
      body, and close the connection (if we opened it).
  2. with-db-transaction -- given 'something', get a connection, start a
      transaction, execute the body, commit/rollback, and close the connection
      (if we opened it else restore connection state)."
  "Database metadata can tell us:
  0. If get generated keys is supported!
  1. If batch updates are supported
  2. If save points are supported
  3. If various concurrency/holdability/etc options are supported")

(set! *warn-on-reflection* true)

(defprotocol Sourceable
  (get-datasource ^DataSource [this]))
(defprotocol Connectable
  (get-connection ^AutoCloseable [this opts]))
(defprotocol Executable
  (-execute ^clojure.lang.IReduceInit [this sql-params opts]))
(defprotocol Preparable
  (prepare ^PreparedStatement [this sql-params opts])
  (prepare-fn ^PreparedStatement [this sql-params factory]))

(defn execute!
  "General SQL execution function.

  Returns a reducible that, when reduced, runs the SQL and yields the result."
  ([stmt] (-execute stmt [] {}))
  ([connectable sql-params & [opts]]
   (-execute connectable sql-params opts)))

(defn set-parameters
  ""
  ^PreparedStatement
  [^PreparedStatement ps params]
  (when (seq params)
    (loop [[p & more] params i 1]
      (.setObject ps i p)
      (when more
        (recur more (inc i)))))
  ps)

(def ^{:private true
       :doc "Map friendly :concurrency values to ResultSet constants."}
  result-set-concurrency
  {:read-only ResultSet/CONCUR_READ_ONLY
   :updatable ResultSet/CONCUR_UPDATABLE})

(def ^{:private true
       :doc "Map friendly :cursors values to ResultSet constants."}
  result-set-holdability
  {:hold ResultSet/HOLD_CURSORS_OVER_COMMIT
   :close ResultSet/CLOSE_CURSORS_AT_COMMIT})

(def ^{:private true
       :doc "Map friendly :type values to ResultSet constants."}
  result-set-type
  {:forward-only ResultSet/TYPE_FORWARD_ONLY
   :scroll-insensitive ResultSet/TYPE_SCROLL_INSENSITIVE
   :scroll-sensitive ResultSet/TYPE_SCROLL_SENSITIVE})

(defn- ^{:tag (class (into-array String []))} string-array
  [return-keys]
  (into-array String return-keys))

(defn- pre-prepare*
  "Given a some options, return a function that will accept a connection and a
  SQL string and parameters, and return a PreparedStatement representing that."
  [{:keys [return-keys result-type concurrency cursors
           fetch-size max-rows timeout]}]
  (cond->
    (cond
     return-keys
     (do
       (when (or result-type concurrency cursors)
         (throw (IllegalArgumentException.
                 (str ":concurrency, :cursors, and :result-type "
                      "may not be specified with :return-keys."))))
       (if (vector? return-keys)
         (let [key-names (string-array return-keys)]
           (fn [^Connection con ^String sql]
             (try
               (try
                 (.prepareStatement con sql key-names)
                 (catch Exception _
                   ;; assume it is unsupported and try regular generated keys:
                   (.prepareStatement con sql java.sql.Statement/RETURN_GENERATED_KEYS)))
               (catch Exception _
                 ;; assume it is unsupported and try basic PreparedStatement:
                 (.prepareStatement con sql)))))
         (fn [^Connection con ^String sql]
           (try
             (.prepareStatement con sql java.sql.Statement/RETURN_GENERATED_KEYS)
             (catch Exception _
               ;; assume it is unsupported and try basic PreparedStatement:
               (.prepareStatement con sql))))))

     (and result-type concurrency)
     (if cursors
       (fn [^Connection con ^String sql]
         (.prepareStatement con sql
                            (get result-set-type result-type result-type)
                            (get result-set-concurrency concurrency concurrency)
                            (get result-set-holdability cursors cursors)))
       (fn [^Connection con ^String sql]
         (.prepareStatement con sql
                            (get result-set-type result-type result-type)
                            (get result-set-concurrency concurrency concurrency))))

     (or result-type concurrency cursors)
     (throw (IllegalArgumentException.
             (str ":concurrency, :cursors, and :result-type "
                  "may not be specified independently.")))
     :else
     (fn [^Connection con ^String sql]
       (.prepareStatement con sql)))
    fetch-size (as-> f
                     (fn [^Connection con ^String sql]
                       (.setFetchSize ^PreparedStatement (f con sql) fetch-size)))
    max-rows (as-> f
                   (fn [^Connection con ^String sql]
                     (.setMaxRows ^PreparedStatement (f con sql) max-rows)))
    timeout (as-> f
                  (fn [^Connection con ^String sql]
                    (.setQueryTimeout ^PreparedStatement (f con sql) timeout)))))

(defn- prepare*
  "Given a connection, a SQL statement, its parameters, and some options,
  return a PreparedStatement representing that."
  [con [sql & params] opts]
  (set-parameters ((pre-prepare* opts) con sql) params))

(defn- prepare-fn*
  "Given a connection, a SQL statement, its parameters, and some options,
  return a PreparedStatement representing that."
  [con [sql & params] factory]
  (set-parameters (factory con sql) params))

(def ^:private isolation-levels
  "Transaction isolation levels."
  {:none             Connection/TRANSACTION_NONE
   :read-committed   Connection/TRANSACTION_READ_COMMITTED
   :read-uncommitted Connection/TRANSACTION_READ_UNCOMMITTED
   :repeatable-read  Connection/TRANSACTION_REPEATABLE_READ
   :serializable     Connection/TRANSACTION_SERIALIZABLE})

(def ^:private isolation-kws
  "Map transaction isolation constants to our keywords."
  (set/map-invert isolation-levels))

(defn get-isolation-level
  "Given an actual JDBC connection, return the current transaction
  isolation level, if known. Return :unknown if we do not recognize
  the isolation level."
  [^Connection jdbc]
  (isolation-kws (.getTransactionIsolation jdbc) :unknown))

(defn committable! [con commit?]
  (when-let [state (:transacted con)]
    (reset! state commit?))
  con)

(defn transact*
  ""
  [con transacted f opts]
  (let [{:keys [isolation read-only? rollback-only?]} opts
        committable? (not rollback-only?)]
    (if transacted
      ;; should check isolation level; maybe implement save points?
      (f con)
      (with-open [^AutoCloseable t-con (assoc (get-connection con opts)
                                              ;; FIXME: not a record/map!
                                              :transacted (atom committable?))]
        (let [^Connection jdbc t-con
              old-autocommit   (.getAutoCommit jdbc)
              old-isolation    (.getTransactionIsolation jdbc)
              old-readonly     (.isReadOnly jdbc)]
          (io!
           (when isolation
             (.setTransactionIsolation jdbc (isolation isolation-levels)))
           (when read-only?
             (.setReadOnly jdbc true))
           (.setAutoCommit jdbc false)
           (try
             (let [result (f t-con)]
               (if @(:transacted t-con)
                 (.commit jdbc)
                 (.rollback jdbc))
               result)
             (catch Throwable t
               (try
                 (.rollback jdbc)
                 (catch Throwable rb
                   ;; combine both exceptions
                   (throw (ex-info (str "Rollback failed handling \""
                                        (.getMessage t)
                                        "\"")
                                   {:rollback rb
                                    :handling t}))))
               (throw t))
             (finally ; tear down
               (committable! t-con committable?)
               ;; the following can throw SQLExceptions but we do not
               ;; want those to replace any exception currently being
               ;; handled -- and if the connection got closed, we just
               ;; want to ignore exceptions here anyway
               (try
                 (.setAutoCommit jdbc old-autocommit)
                 (catch Exception _))
               (when isolation
                 (try
                   (.setTransactionIsolation jdbc old-isolation)
                   (catch Exception _)))
               (when read-only?
                 (try
                   (.setReadOnly jdbc old-readonly)
                   (catch Exception _)))))))))))

(defmacro in-transaction
  [[sym con opts] & body]
  `(transact* ~con (fn [~sym] ~@body) ~opts))

(def ^:private classnames
  "Map of subprotocols to classnames. dbtype specifies one of these keys.

  The subprotocols map below provides aliases for dbtype.

  Most databases have just a single class name for their driver but we
  support a sequence of class names to try in order to allow for drivers
  that change their names over time (e.g., MySQL)."
  {"derby"          "org.apache.derby.jdbc.EmbeddedDriver"
   "h2"             "org.h2.Driver"
   "h2:mem"         "org.h2.Driver"
   "hsqldb"         "org.hsqldb.jdbcDriver"
   "jtds:sqlserver" "net.sourceforge.jtds.jdbc.Driver"
   "mysql"          ["com.mysql.cj.jdbc.Driver"
                     "com.mysql.jdbc.Driver"]
   "oracle:oci"     "oracle.jdbc.OracleDriver"
   "oracle:thin"    "oracle.jdbc.OracleDriver"
   "postgresql"     "org.postgresql.Driver"
   "pgsql"          "com.impossibl.postgres.jdbc.PGDriver"
   "redshift"       "com.amazon.redshift.jdbc.Driver"
   "sqlite"         "org.sqlite.JDBC"
   "sqlserver"      "com.microsoft.sqlserver.jdbc.SQLServerDriver"})

(def ^:private aliases
  "Map of schemes to subprotocols. Used to provide aliases for dbtype."
  {"hsql"       "hsqldb"
   "jtds"       "jtds:sqlserver"
   "mssql"      "sqlserver"
   "oracle"     "oracle:thin"
   "oracle:sid" "oracle:thin"
   "postgres"   "postgresql"})

(def ^:private host-prefixes
  "Map of subprotocols to non-standard host-prefixes.
  Anything not listed is assumed to use //."
  {"oracle:oci"  "@"
   "oracle:thin" "@"})

(def ^:private ports
  "Map of subprotocols to ports."
  {"jtds:sqlserver" 1433
   "mysql"          3306
   "oracle:oci"     1521
   "oracle:sid"     1521
   "oracle:thin"    1521
   "postgresql"     5432
   "sqlserver"      1433})

(def ^:private dbname-separators
  "Map of schemes to separators. The default is / but a couple are different."
  {"mssql"      ";DATABASENAME="
   "sqlserver"  ";DATABASENAME="
   "oracle:sid" ":"})

(defn- modify-connection
  "Given a database connection and a map of options, update the connection
  as specified by the options."
  ^Connection
  [^Connection connection opts]
  (when (and connection (contains? opts :auto-commit?))
    (.setAutoCommit connection (boolean (:auto-commit? opts))))
  (when (and connection (contains? opts :read-only?))
    (.setReadOnly connection (boolean (:read-only? opts))))
  connection)

(defn- ^Properties as-properties
  "Convert any seq of pairs to a java.utils.Properties instance.
   Uses as-sql-name to convert both keys and values into strings."
  [m]
  (let [p (Properties.)]
    (doseq [[k v] m]
      (.setProperty p (name k) (str v)))
    p))

(defn- get-driver-connection
  "Common logic for loading the DriverManager and the designed JDBC driver
  class and obtaining the appropriate Connection object."
  [url etc]
  ;; force DriverManager to be loaded
  (DriverManager/getLoginTimeout)
  (DriverManager/getConnection url (as-properties etc)))

(defn- spec->url+etc
  ""
  [{:keys [dbtype dbname host port classname] :as db-spec}]
  (let [;; allow aliases for dbtype
        subprotocol (aliases dbtype dbtype)
        host (or host "127.0.0.1")
        port (or port (ports subprotocol))
        db-sep (dbname-separators dbtype "/")
        url (cond (= "h2:mem" dbtype)
                  (str "jdbc:" subprotocol ":" dbname ";DB_CLOSE_DELAY=-1")
                  (#{"derby" "h2" "hsqldb" "sqlite"} subprotocol)
                  (str "jdbc:" subprotocol ":" dbname)
                  :else
                  (str "jdbc:" subprotocol ":"
                       (host-prefixes subprotocol "//")
                       host
                       (when port (str ":" port))
                       db-sep dbname))
        etc (dissoc db-spec :dbtype :dbname)]
    ;; verify the datasource is loadable
    (if-let [class-name (or classname (classnames subprotocol))]
      (do
        (if (string? class-name)
          (clojure.lang.RT/loadClassForName class-name)
          (loop [[clazz & more] class-name]
            (when-let [load-failure
                       (try
                         (clojure.lang.RT/loadClassForName clazz)
                         nil
                         (catch Exception e
                           e))]
              (if (seq more)
                (recur more)
                (throw load-failure))))))
      (throw (ex-info (str "Unknown dbtype: " dbtype) db-spec)))
    [url etc]))

(defn- string->url+etc
  ""
  [s]
  [s {}])

(defn- url+etc->datasource
  ""
  [[url etc]]
  (reify DataSource
    (getConnection [_]
                   (get-driver-connection url etc))
    (getConnection [_ username password]
                   (get-driver-connection url
                                          (assoc etc
                                                 :username username
                                                 :password password)))))

(extend-protocol Sourceable
  clojure.lang.Associative
  (get-datasource [this]
                  (url+etc->datasource (spec->url+etc this)))
  DataSource
  (get-datasource [this] this)
  String
  (get-datasource [this]
                  (url+etc->datasource (string->url+etc this))))

(extend-protocol Connectable
  DataSource
  (get-connection [this opts] (-> (.getConnection this)
                                  (modify-connection opts)))
  Object
  (get-connection [this opts] (get-connection (get-datasource this) opts)))

(extend-protocol Preparable
  Connection
  (prepare [this sql-params opts]
           (prepare* this sql-params opts))
  (prepare-fn [this sql-params factory]
              (prepare-fn* this sql-params factory))
  DataSource
  (prepare [this sql-params opts]
           (prepare (.getConnection this) sql-params opts))
  (prepare-fn [this sql-params factory]
              (prepare-fn (.getConnection this) sql-params factory))
  Object
  (prepare [this sql-params opts]
           (prepare (get-datasource this) sql-params opts))
  (prepare-fn [this sql-params factory]
              (prepare-fn (get-datasource this) sql-params factory)))

(defn- get-column-names
  ""
  [^ResultSet rs]
  (let [^ResultSetMetaData rsmeta (.getMetaData rs)
        idxs (range 1 (inc (.getColumnCount rsmeta)))]
    (mapv (fn [^Integer i]
            (keyword (.getTableName rsmeta i)
                     (.getColumnLabel rsmeta i)))
          idxs)))

(defn- mapify-result-set
  "Given a result set, return an object that wraps the current row as a hash
  map. Note that a result set is mutable and the current row will change behind
  this wrapper so operations need to be eager (and fairly limited).

  Supports ILookup (keywords are treated as strings).

  Supports Associative (again, keywords are treated as strings).

  Supports Seqable which realizes a full row of the data.

  Later we may realize a new hash map when assoc (and other, future, operations
  are performed on the result set row)."
  [^ResultSet rs]
  (let [cols (delay (get-column-names rs))]
    (reify

      clojure.lang.ILookup
      (valAt [this k]
             (try
               (.getObject rs (name k))
               (catch SQLException _)))
      (valAt [this k not-found]
             (try
               (.getObject rs (name k))
               (catch SQLException _
                 not-found)))

      clojure.lang.Associative
      (containsKey [this k]
                   (try
                     (.getObject rs (name k))
                     true
                     (catch SQLException _
                       false)))
      (entryAt [this k]
               (try
                 (clojure.lang.MapEntry. k (.getObject rs (name k)))
                 (catch SQLException _)))
      (assoc [this k v]
             (assoc (into {} (seq this)) k v))

      clojure.lang.Seqable
      (seq [this]
           (seq (mapv (fn [^Integer i]
                        (clojure.lang.MapEntry. (nth @cols (dec i))
                                                (.getObject rs i)))
                      (range 1 (inc (count @cols)))))))))

(defn- reduce-stmt
  ""
  [^PreparedStatement stmt f init]
  (if (.execute stmt)
    (let [rs     (.getResultSet stmt)
          rs-map (mapify-result-set rs)]
      (loop [init' init]
        (if (.next rs)
          (let [result (f init' rs-map)]
            (if (reduced? result)
              @result
              (recur result)))
          init')))
    (f init (.getUpdateCount stmt))))

(extend-protocol Executable
  Connection
  (-execute [this sql-params opts]
            (let [factory (pre-prepare* opts)]
              (reify clojure.lang.IReduceInit
                (reduce [_ f init]
                        (with-open [stmt (prepare-fn this sql-params factory)]
                          (reduce-stmt stmt f init))))))
  DataSource
  (-execute [this sql-params opts]
            (let [factory (pre-prepare* opts)]
              (reify clojure.lang.IReduceInit
                (reduce [_ f init]
                        (with-open [con (get-connection this opts)]
                          (with-open [stmt (prepare-fn con sql-params factory)]
                            (reduce-stmt stmt f init)))))))
  PreparedStatement
  (-execute [this _ _]
            (reify clojure.lang.IReduceInit
              (reduce [_ f init] (reduce-stmt this f init))))
  Object
  (-execute [this sql-params opts]
            (-execute (get-datasource this) sql-params opts)))

(defn query
  ""
  [connectable sql-params & [opts]]
  (into []
        (map (or (:row-fn opts) (partial into {})))
        (execute! connectable sql-params opts)))

(defn query-one
  ""
  [connectable sql-params & [opts]]
  (reduce (fn [_ row] (reduced ((or (:row-fn opts) (partial into {})) row)))
          nil
          (execute! connectable sql-params opts)))

(defn command!
  ""
  [connectable sql-params & [opts]]
  (reduce + 0 (execute! connectable sql-params opts)))

(comment
  (def db-spec {:dbtype "h2:mem" :dbname "perf"})
  (def con db-spec)
  (def con (get-datasource db-spec))
  (get-connection con {})
  (def con (get-connection (get-datasource db-spec) {}))
  (def con (get-connection db-spec {}))
  (command! con ["DROP TABLE fruit"])
  (command! con ["CREATE TABLE fruit (id int default 0, name varchar(32) primary key, appearance varchar(32), cost int, grade real)"])
  (command! con ["INSERT INTO fruit (id,name,appearance,cost,grade) VALUES (1,'Apple','red',59,87), (2,'Banana','yellow',29,92.2), (3,'Peach','fuzzy',139,90.0), (4,'Orange','juicy',89,88.6)"])

  (println con)
  (.close con)

  (require '[criterium.core :refer [bench quick-bench]])

  ;; calibrate
  (quick-bench (reduce + (take 10e6 (range))))

  ;; raw java
  (defn select* [^Connection con]
    (let [ps (doto (.prepareStatement con "SELECT * FROM fruit WHERE appearance = ?")
               (.setObject 1 "red"))
          rs (.executeQuery ps)
          _ (.next rs)
          value (.getObject rs "name")]
      (.close ps)
      value))
  (quick-bench (select* con))

  ;; same as the Java example in java.jdbc perf test
  (quick-bench
   (reduce (fn [rs m] (reduced (:name m)))
           nil
           (execute! con ["select * from fruit where appearance = ?" "red"])))
  (quick-bench
   (query-one con
              ["select * from fruit where appearance = ?" "red"]
              {:row-fn :name}))

  ;; simple query
  (quick-bench
   (query con ["select * from fruit where appearance = ?" "red"]))

  ;; with a prepopulated prepared statement
  (with-open [ps (prepare con ["select * from fruit where appearance = ?" "red"] {})]
    (quick-bench
     [(reduce (fn [_ row] (reduced (:name row)))
              nil
              (execute! ps))]))

  ;; same as above but setting parameters inside the benchmark
  (with-open [ps (prepare con ["select * from fruit where appearance = ?"] {})]
    (quick-bench
     [(reduce (fn [_ row] (reduced (:name row)))
              nil
              (execute! (set-parameters ps ["red"])))]))

  ;; this takes more than twice the time of the one above which seems strange
  (with-open [ps (prepare con ["select * from fruit where appearance = ?"] {})]
    (quick-bench
     [(reduce (fn [_ row] (reduced (:name row)))
              nil
              (execute! (set-parameters ps ["red"])))
      (reduce (fn [_ row] (reduced (:name row)))
              nil
              (execute! (set-parameters ps ["fuzzy"])))]))

  ;; full first row
  (quick-bench
   (query-one con ["select * from fruit where appearance = ?" "red"]))

  ;; test assoc works
  (query-one con
             ["select * from fruit where appearance = ?" "red"]
             {:row-fn #(assoc % :test :value)})
  ;; test assoc works
  (query con
         ["select * from fruit where appearance = ?" "red"]
         {:row-fn #(assoc % :test :value)}))