Re: POC: Lock updated tuples in tuple_update() and tuple_delete()

Hi Alexander,

> I'm going to push this if no objections.

I took a fresh look at the patch and it LGTM. I only did a few
cosmetic changes, PFA v7.

Changes since v6 are:

```
@@ -318,12 +318,12 @@ heapam_tuple_delete(Relation relation,
ItemPointer tid, CommandId cid,
result = heap_delete(relation, tid, cid, crosscheck, wait, tmfd,
changingPart);

/*
- * If the tuple has been concurrently updated, get lock already so that on
- * retry it will succeed, provided that the caller asked to do this by
- * providing a lockedSlot.
+ * If lockUpdated is true and the tuple has been concurrently updated, get
+ * the lock immediately so that on retry we will succeed.
*/
if (result == TM_Updated && lockUpdated)
{
+ Assert(lockedSlot != NULL);
```

... and the same for heapam_tuple_update().

--
Best regards,
Aleksander Alekseev