Horton

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

Aleksander Alekseev <aleksander@timescale.com>

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From: Aleksander Alekseev <aleksander@timescale.com>
To: pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: Alexander Korotkov <aekorotkov@gmail.com>
Date: 2022-07-05T13:38:28Z
Lists: pgsql-hackers 
Hi Alexander,

> Thoughts and feedback are welcome.

I took some preliminary look at the patch. I'm going to need more time
to meditate on the proposed changes and to figure out the performance
impact.

So far I just wanted to let you know that the patch applied OK for me
and passed all the tests. The `else` branch here seems to be redundant
here:

+        if (!updated)
+        {
+            /* Should not encounter speculative tuple on recheck */
+            Assert(!HeapTupleHeaderIsSpeculative(tuple->t_data));
-             ReleaseBuffer(buffer);
+            ReleaseBuffer(buffer);
+        }
+        else
+        {
+            updated = false;
+        }

Also I wish there were a little bit more comments since some of the
proposed changes are not that straightforward.

-- 
Best regards,
Aleksander Alekseev

Commits

  1. Add EvalPlanQual delete returning isolation test

  2. Allow locking updated tuples in tuple_update() and tuple_delete()

  3. Revert 764da7710b

  4. Revert 11470f544e

  5. Evade extra table_tuple_fetch_row_version() in ExecUpdate()/ExecDelete()

  6. Check that xmax didn't commit in freeze check.