Re: BUG #16139: Assertion fails on INSERT into a postgres_fdw' tablewith two AFTER INSERT triggers

On Wed, Nov 27, 2019 at 8:35 PM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
> A bit of investigation showed that this is caused by commit
> ff11e7f4b9ae017585c3ba146db7ba39c31f209a.  I haven't yet looked at the
> commit in any detail, though.

I spent some time studying the commit.  I think AfterTriggerExecute()
should make sure that:

 * foreign tables always use zero and save the tuple(s) to a
 * tuplestore.  AFTER_TRIGGER_FDW_FETCH directs AfterTriggerExecute() to
 * retrieve a fresh tuple or pair of tuples from that tuplestore, while
 * AFTER_TRIGGER_FDW_REUSE directs it to use the most-recently-retrieved
 * tuple(s).  This permits storing tuples once regardless of the number of
 * row-level triggers on a foreign table.

But the commit modified that function to clear the tg_trigslot and
tg_newslot slots' contents, which are reused when
AFTER_TRIGGER_FDW_REUSE, as shown below:

@@ -4374,12 +4373,17 @@ AfterTriggerExecute(AfterTriggerEvent event,
        heap_freetuple(rettuple);

    /*
-    * Release buffers
+    * Release resources
     */
-   if (buffer1 != InvalidBuffer)
-       ReleaseBuffer(buffer1);
-   if (buffer2 != InvalidBuffer)
-       ReleaseBuffer(buffer2);
+   if (should_free_trig)
+       heap_freetuple(LocTriggerData.tg_trigtuple);
+   if (should_free_new)
+       heap_freetuple(LocTriggerData.tg_newtuple);
+
+   if (LocTriggerData.tg_trigslot)
+       ExecClearTuple(LocTriggerData.tg_trigslot);
+   if (LocTriggerData.tg_newslot)
+       ExecClearTuple(LocTriggerData.tg_newslot);

Attached is a patch for fixing that.  Maybe I'm missing something, though.

Best regards,
Etsuro Fujita