Fix transaction() not actually using a transaction

.gitignore

@@ -40,3 +40,5 @@ deps/build.log
 
 # Manifest file
 Manifest.toml
+
+.vscode/

src/load.jl

@@ -105,14 +105,12 @@ function load(itr, conn::Connection, name::AbstractString="mysql_"*Random.randst
 end
 
 function transaction(f::Function, conn)
-    API.autocommit(conn.mysql, false)
+    execute(conn, "START TRANSACTION")
     try
         f()
         API.commit(conn.mysql)
     catch
         API.rollback(conn.mysql)
         rethrow()
-    finally
-        API.autocommit(conn.mysql, true)
     end
 end

test/runtests.jl

@@ -350,3 +350,39 @@ ret = columntable(res)
 
 # load on closed connection should throw
 @test_throws ArgumentError MySQL.load(ct, conn, "test194")
+
+@testset "transactions" begin
+    DBInterface.execute(conn, "DROP TABLE IF EXISTS TransactionTest")
+    DBInterface.execute(conn, "CREATE TABLE TransactionTest (a int)")
+
+    conn2 = DBInterface.connect(MySQL.Connection, "", ""; option_file=joinpath(dirname(pathof(MySQL)), "../test/", "my.ini"))
+
+    try
+        # happy path
+        DBInterface.transaction(conn) do
+            DBInterface.execute(conn, "INSERT INTO TransactionTest (a) VALUES (1)")
+
+            # we can see the result inside our transaction
+            result = DBInterface.execute(conn, "SELECT * FROM TransactionTest") |> Tables.columntable
+            @test result.a == [1]
+
+            # and can't see it outside our transaction
+            result = DBInterface.execute(conn2, "SELECT * FROM TransactionTest") |> Tables.columntable
+            @test isempty(result.a)
+        end
+        result = DBInterface.execute(conn, "SELECT * FROM TransactionTest") |> Tables.columntable
+        @test result.a == [1]
+        result = DBInterface.execute(conn2, "SELECT * FROM TransactionTest") |> Tables.columntable
+        @test result.a == [1]
+
+        # roll back due to exception
+        @test_throws ErrorException DBInterface.transaction(conn) do
+            DBInterface.execute(conn, "INSERT INTO TransactionTest (a) VALUES (2)")
+            error("force rollback")
+        end
+        result = DBInterface.execute(conn, "SELECT * FROM TransactionTest") |> Tables.columntable
+        @test result.a == [1] # the table did not change
+    finally
+        close(conn2)
+    end
+end