Remove simple protocol and one round trip query options

It is impossible to guarantee that the a query executed with the simple
protocol will behave the same as with the extended protocol. This is
because the normal pgx path relies on knowing the OID of query
parameters. Without this encoding a value can only be determined by the
value instead of the combination of value and PostgreSQL type. For
example, how should a []int32 be encoded? It might be encoded into a
PostgreSQL int4[] or json.

Removal also simplifies the core query path.

The primary reason for the simple protocol is for servers like PgBouncer
that may not be able to support normal prepared statements. After
further research it appears that issuing a "flush" instead "sync" after
preparing the unnamed statement would allow PgBouncer to work.

The one round trip mode can be better handled with prepared statements.

As a last resort, all original server functionality can still be accessed by
dropping down to PgConn.

cid_test.go

@@ -20,9 +20,6 @@ func TestCIDTranscode(t *testing.T) {
 
 	testutil.TestPgxSuccessfulTranscodeEqFunc(t, pgTypeName, values, eqFunc)
 
-	// No direct conversion from int to cid, convert through text
-	testutil.TestPgxSimpleProtocolSuccessfulTranscodeEqFunc(t, "text::"+pgTypeName, values, eqFunc)
-
 	for _, driverName := range []string{"github.com/lib/pq", "github.com/jackc/pgx/stdlib"} {
 		testutil.TestDatabaseSQLSuccessfulTranscodeEqFunc(t, driverName, pgTypeName, values, eqFunc)
 	}

testutil/testutil.go

@@ -98,7 +98,6 @@ func TestSuccessfulTranscode(t testing.TB, pgTypeName string, values []interface
 
 func TestSuccessfulTranscodeEqFunc(t testing.TB, pgTypeName string, values []interface{}, eqFunc func(a, b interface{}) bool) {
 	TestPgxSuccessfulTranscodeEqFunc(t, pgTypeName, values, eqFunc)
-	TestPgxSimpleProtocolSuccessfulTranscodeEqFunc(t, pgTypeName, values, eqFunc)
 	for _, driverName := range []string{"github.com/lib/pq", "github.com/jackc/pgx/stdlib"} {
 		TestDatabaseSQLSuccessfulTranscodeEqFunc(t, driverName, pgTypeName, values, eqFunc)
 	}
@@ -150,35 +149,6 @@ func TestPgxSuccessfulTranscodeEqFunc(t testing.TB, pgTypeName string, values []
 	}
 }
 
-func TestPgxSimpleProtocolSuccessfulTranscodeEqFunc(t testing.TB, pgTypeName string, values []interface{}, eqFunc func(a, b interface{}) bool) {
-	conn := MustConnectPgx(t)
-	defer MustCloseContext(t, conn)
-
-	for i, v := range values {
-		// Derefence value if it is a pointer
-		derefV := v
-		refVal := reflect.ValueOf(v)
-		if refVal.Kind() == reflect.Ptr {
-			derefV = refVal.Elem().Interface()
-		}
-
-		result := reflect.New(reflect.TypeOf(derefV))
-		err := conn.QueryRow(
-			context.Background(),
-			fmt.Sprintf("select ($1)::%s", pgTypeName),
-			&pgx.QueryExOptions{SimpleProtocol: true},
-			v,
-		).Scan(result.Interface())
-		if err != nil {
-			t.Errorf("Simple protocol %d: %v", i, err)
-		}
-
-		if !eqFunc(result.Elem().Interface(), derefV) {
-			t.Errorf("Simple protocol %d: expected %v, got %v", i, derefV, result.Elem().Interface())
-		}
-	}
-}
-
 func TestDatabaseSQLSuccessfulTranscodeEqFunc(t testing.TB, driverName, pgTypeName string, values []interface{}, eqFunc func(a, b interface{}) bool) {
 	conn := MustConnectDatabaseSQL(t, driverName)
 	defer MustClose(t, conn)

xid_test.go

@@ -20,9 +20,6 @@ func TestXIDTranscode(t *testing.T) {
 
 	testutil.TestPgxSuccessfulTranscodeEqFunc(t, pgTypeName, values, eqFunc)
 
-	// No direct conversion from int to xid, convert through text
-	testutil.TestPgxSimpleProtocolSuccessfulTranscodeEqFunc(t, "text::"+pgTypeName, values, eqFunc)
-
 	for _, driverName := range []string{"github.com/lib/pq", "github.com/jackc/pgx/stdlib"} {
 		testutil.TestDatabaseSQLSuccessfulTranscodeEqFunc(t, driverName, pgTypeName, values, eqFunc)
 	}