chore: delay transaction activation until actual use (#552)

* chore: store temp TransactionOptions in connection state

Store temporary TransactionOptions in the connection state as local options. Local options
only apply to the current transaction. This simplifies the internal state handling of the
driver, as all transaction state should only be read from the connection state, and not
also from a temporary variable.

This also enables the use of a combination of temporary transaction options and using
SQL statements to set further options. The shared library always includes temporary
transaction options, as the BeginTransaction function accepts TransactionOptions as an
input argument. This meant that using SQL statements to set further transaction options
was not supported through the shared library.

* chore: delay transaction activation until actual use

Delay the actual transaction activation until the first actual usage of the transaction.
That is; the first time that a statement is being sent to Spanner. This allows the
application to amend the transaction options after calling BeginTx or executing
`BEGIN TRANSACTION`. The transaction options can be amended by executing a statement
like `SET TRANSACTION READ ONLY`.

Author: olavloite

aborted_transactions_test.go

@@ -41,6 +41,9 @@ func TestCommitAborted(t *testing.T) {
 	if err != nil {
 		t.Fatalf("begin failed: %v", err)
 	}
+	if _, err := tx.ExecContext(ctx, testutil.UpdateBarSetFoo); err != nil {
+		t.Fatal(err)
+	}
 	server.TestSpanner.PutExecutionTime(testutil.MethodCommitTransaction, testutil.SimulatedExecutionTime{
 		Errors: []error{status.Error(codes.Aborted, "Aborted")},
 	})
@@ -51,7 +54,7 @@ func TestCommitAborted(t *testing.T) {
 	reqs := server.TestSpanner.DrainRequestsFromServer()
 	commitReqs := testutil.RequestsOfType(reqs, reflect.TypeOf(&sppb.CommitRequest{}))
 	if g, w := len(commitReqs), 2; g != w {
-		t.Fatalf("commit request count mismatch\nGot: %v\nWant: %v", g, w)
+		t.Fatalf("commit request count mismatch\n Got: %v\nWant: %v", g, w)
 	}
 
 	// Verify that the db is still usable.
@@ -117,6 +120,9 @@ func TestCommitAbortedWithInternalRetriesDisabled(t *testing.T) {
 	if err != nil {
 		t.Fatalf("begin failed: %v", err)
 	}
+	if _, err := tx.ExecContext(ctx, testutil.UpdateBarSetFoo); err != nil {
+		t.Fatal(err)
+	}
 	server.TestSpanner.PutExecutionTime(testutil.MethodCommitTransaction, testutil.SimulatedExecutionTime{
 		Errors: []error{status.Error(codes.Aborted, "Aborted")},
 	})

client_side_statement_test.go

@@ -65,7 +65,7 @@ func TestStatementExecutor_StartBatchDdl(t *testing.T) {
 	}
 
 	// Starting a DDL batch while the connection is in a transaction is not allowed.
-	c.tx = &readWriteTransaction{}
+	c.tx = &delegatingTransaction{conn: c, ctx: ctx}
 	if _, err := c.ExecContext(ctx, "start batch ddl", []driver.NamedValue{}); spanner.ErrCode(err) != codes.FailedPrecondition {
 		t.Fatalf("error mismatch for starting a DDL batch while in a transaction\nGot: %v\nWant: %v", spanner.ErrCode(err), codes.FailedPrecondition)
 	}
@@ -102,13 +102,13 @@ func TestStatementExecutor_StartBatchDml(t *testing.T) {
 	}
 
 	// Starting a DML batch while the connection is in a read-only transaction is not allowed.
-	c.tx = &readOnlyTransaction{logger: noopLogger}
+	c.tx = &delegatingTransaction{conn: c, contextTransaction: &readOnlyTransaction{logger: noopLogger}}
 	if _, err := c.ExecContext(ctx, "start batch dml", []driver.NamedValue{}); spanner.ErrCode(err) != codes.FailedPrecondition {
 		t.Fatalf("error mismatch for starting a DML batch while in a read-only transaction\nGot: %v\nWant: %v", spanner.ErrCode(err), codes.FailedPrecondition)
 	}
 
 	// Starting a DML batch while the connection is in a read/write transaction is allowed.
-	c.tx = &readWriteTransaction{logger: noopLogger}
+	c.tx = &delegatingTransaction{conn: c, contextTransaction: &readWriteTransaction{logger: noopLogger}}
 	if _, err := c.ExecContext(ctx, "start batch dml", []driver.NamedValue{}); err != nil {
 		t.Fatalf("could not start a DML batch while in a read/write transaction: %v", err)
 	}