Allow creation of Transaction/AsyncTransaction from TxnContext

[EnricoMi]

This PR adds support for creating a new transaction from DgraphClient and DgraphAsyncClient using an existing TxnContext.

This change is 

[CLAassistant]

All committers have signed the CLA.

[EnricoMi]

@gitlw @deepakjois @mangalaman93 please let me know what you think about this, it is tested to give me what I need for the Spark Dgraph connector (see linked PR)

[abhimanyusinghgaur]

Hi @EnricoMi,

Thanks for the PR.

I have seen your post in discuss, I will take a look at it by the end of the week.

[EnricoMi]

Thanks, that's appreciated!

[abhimanyusinghgaur]

just got some minor comments, please let me know when you update the PR and I can merge it.

It is really a nice idea to expose TxnContext to users.

Thank you @EnricoMi for this nice PR.
Cheers!

Reviewed 5 of 5 files at r1.
Reviewable status: all files reviewed, 7 unresolved discussions (waiting on @EnricoMi)

---

src/main/java/io/dgraph/AsyncTransaction.java, line 61 at r1 (raw file):

Quoted 10 lines of code…

  AsyncTransaction(DgraphAsyncClient client, DgraphStub stub, TxnContext context) {
    this(client, stub);
    this.context = context;
  }
  AsyncTransaction(
      DgraphAsyncClient client, DgraphStub stub, TxnContext context, final boolean readOnly) {
    this(client, stub, context);
    this.context = context;
    this.readOnly = readOnly;
  }

Just a minor thing, but I feel like these two constructors should go after this one: AsyncTransaction(DgraphAsyncClient client, DgraphStub stub, final boolean readOnly)

---

src/test/java/io/dgraph/DgraphAsyncClientTest.java, line 112 at r1 (raw file):

).get()

nitpicking, but we prefer join over get.

---

src/test/java/io/dgraph/DgraphAsyncClientTest.java, line 112 at r1 (raw file):

uid(0x0)

Although, this works currently. But, just to clarify, 0x0 is not a uid that is ever allocated. Uids always start from 0x1. So, maybe use 0x1 in all the test queries.

---

src/test/java/io/dgraph/DgraphAsyncClientTest.java, line 121 at r1 (raw file):

).get();

join over get again.

---

src/test/java/io/dgraph/DgraphAsyncClientTest.java, line 121 at r1 (raw file):

0x0

0x1

---

src/test/java/io/dgraph/DgraphClientTest.java, line 107 at r1 (raw file):

0x0

0x1

---

src/test/java/io/dgraph/DgraphClientTest.java, line 116 at r1 (raw file):

0x0

0x1

[abhimanyusinghgaur]

Reviewable status: 2 of 5 files reviewed, 2 unresolved discussions (waiting on @abhimanyusinghgaur and @EnricoMi)

---

src/test/java/io/dgraph/DgraphAsyncClientTest.java, line 109 at r2 (raw file):

  @Test
  public void testNewTransactionFromContext() throws Exception {

I guess, you won't need throws Exception anymore as all the exceptions returned by join are runtime exceptions.

---

src/test/java/io/dgraph/DgraphAsyncClientTest.java, line 118 at r2 (raw file):

  @Test
  public void testNewReadOnlyTransactionFromContext() throws Exception {

throws Exception can be removed.

[EnricoMi]

Thanks for merging this! Any estimate on when this will be part of a release? Or can you provide me a snapshot version?

[abhimanyusinghgaur]

Umm..., we are gonna do a major release for dgraph by the end of July, and I think we will also release a new version of this client in sync with the dgraph release, as it has got some updates. But, let me confirm, and update you on this.