ensure exec and scalar release connection

ensure exec, query can be executed with Enumerable(Any)
update db doc sample

spec/std/db/db_spec.cr

@@ -69,4 +69,18 @@ describe DB do
       end
     end
   end
+
+  it "exec should return to pool" do
+    with_dummy do |db|
+      db.exec "foo"
+      db.exec "bar"
+    end
+  end
+
+  it "scalar should return to pool" do
+    with_dummy do |db|
+      db.scalar "foo"
+      db.scalar "bar"
+    end
+  end
 end

spec/std/db/statement_spec.cr

@@ -19,6 +19,16 @@ describe DB::Statement do
     end
   end
 
+  it "should initialize positional params in query with array" do
+    with_dummy do |db|
+      stmt = db.prepare("the query")
+      stmt.query ["a", 1, nil]
+      stmt.params[0].should eq("a")
+      stmt.params[1].should eq(1)
+      stmt.params[2].should eq(nil)
+    end
+  end
+
   it "should initialize positional params in exec" do
     with_dummy do |db|
       stmt = db.prepare("the query")
@@ -29,6 +39,16 @@ describe DB::Statement do
     end
   end
 
+  it "should initialize positional params in exec with array" do
+    with_dummy do |db|
+      stmt = db.prepare("the query")
+      stmt.exec ["a", 1, nil]
+      stmt.params[0].should eq("a")
+      stmt.params[1].should eq(1)
+      stmt.params[2].should eq(nil)
+    end
+  end
+
   it "should initialize positional params in scalar" do
     with_dummy do |db|
       stmt = db.prepare("the query")

src/db/db.cr

@@ -14,14 +14,14 @@ require "uri"
 # Assuming `crystal-sqlite3` is included a sqlite3 database can be opened with `#open`.
 #
 # ```
-# db = DB.open "sqlite3://%3Amemory%3A" # or sqlite3:///path/to/db/file.db
+# db = DB.open "sqlite3:%3Amemory%3A" # or sqlite3:./path/to/db/file.db
 # db.close
 # ```
 #
 # If a block is given to `#open` the database is closed automatically
 #
 # ```
-# DB.open "sqlite3://%3Amemory%3A" do |db|
+# DB.open "sqlite3:%3Amemory%3A" do |db|
 #   # work with db
 # end # db is closed
 # ```
@@ -42,7 +42,11 @@ require "uri"
 # DB.open "sqlite3://%3Amemory%3A" do |db|
 #   db.exec "create table contacts (name string, age integer)"
 #   db.exec "insert into contacts values (?, ?)", "John Doe", 30
-#   db.exec "insert into contacts values (:name, :age)", {name: "Sarah", age: 33}
+#
+#   args = [] of DB::Any
+#   args << "Sarah"
+#   args << 33
+#   db.exec "insert into contacts values (?, ?)", args
 #
 #   puts "max age:"
 #   puts db.scalar "select max(age) from contacts" # => 33

src/db/result_set.cr

@@ -22,8 +22,7 @@ module DB
     end
 
     protected def do_close
-      cnn = statement.connection
+      statement.release_connection
-      cnn.database.return_to_pool(cnn)
     end
 
     # TODO add_next_result_set : Bool

src/db/statement.cr

@@ -21,15 +21,24 @@ module DB
     protected def do_close
     end
 
+    def release_connection
+      @connection.database.return_to_pool(@connection)
+    end
+
     # See `QueryMethods#exec`
     def exec
-      perform_exec(Slice(Any).new(0)) # no overload matches ... with types Slice(NoReturn)
+      perform_exec_and_release(Slice(Any).new(0)) # no overload matches ... with types Slice(NoReturn)
+    end
+
+    # See `QueryMethods#exec`
+    def exec(args : Enumerable(Any))
+      perform_exec_and_release(args.to_a.to_unsafe.to_slice(args.size))
     end
 
     # See `QueryMethods#exec`
     def exec(*args)
       # TODO better way to do it
-      perform_exec(args.to_a.to_unsafe.to_slice(args.size))
+      perform_exec_and_release(args.to_a.to_unsafe.to_slice(args.size))
     end
 
     # See `QueryMethods#scalar`
@@ -81,11 +90,22 @@ module DB
       perform_query(Slice(Any).new(0)) # no overload matches ... with types Slice(NoReturn)
     end
 
+    private def perform_query(args : Enumerable(Any)) : ResultSet
+      # TODO better way to do it
+      perform_query(args.to_a.to_unsafe.to_slice(args.size))
+    end
+
     private def perform_query(*args) : ResultSet
       # TODO better way to do it
       perform_query(args.to_a.to_unsafe.to_slice(args.size))
     end
 
+    private def perform_exec_and_release(args : Slice(Any)) : ExecResult
+      perform_exec(args).tap do
+        release_connection
+      end
+    end
+
     protected abstract def perform_query(args : Slice(Any)) : ResultSet
     protected abstract def perform_exec(args : Slice(Any)) : ExecResult
   end