PERF: Optimize multiple use param in prepared postgres sql (#46)

lib/mini_sql/postgres/prepared_binds.rb

@@ -6,6 +6,33 @@ module MiniSql
   module Postgres
     class PreparedBinds < ::MiniSql::Abstract::PreparedBinds
 
+      def bind_hash(sql, hash)
+        sql = sql.dup
+        binds = []
+        bind_names = []
+        i = 0
+
+        hash.each do |k, v|
+          bind_outputs =
+            array_wrap(v).map { |vv|
+              binds << vv
+              bind_names << [BindName.new(k)]
+              bind_output(i += 1)
+            }.join(', ')
+
+          sql.gsub!(":#{k}") do
+            # ignore ::int and stuff like that
+            # $` is previous to match
+            if $` && $`[-1] != ":"
+              bind_outputs
+            else
+              ":#{k}"
+            end
+          end
+        end
+        [sql, binds, bind_names]
+      end
+
       def bind_output(i)
         "$#{i}"
       end

test/mini_sql/postgres/prepared_connection_test.rb

@@ -61,4 +61,11 @@ def test_limit_prepared_cache
     assert_equal ps[0].statement, 'SELECT $1, $2, $3'
   end
 
+  def test_single_named_param
+    r = @prepared_connection.query_single("select :n, :n, :n", n: 'test')
+
+    assert_last_stmt "select $1, $1, $1"
+    assert_equal %w[test test test], r
+  end
+
 end