Date: Tue, 12 May 2026 19:30:11 +0900
From: Yugo Nagata <nagata@sraoss.co.jp>
To: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>, PostgreSQL Hackers
 <pgsql-hackers@lists.postgresql.org>
Subject: Re: Infinite Autovacuum loop caused by failing virtual generated
 column expression
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On Sun, 3 May 2026 11:04:59 -0700
SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com> wrote:

Thank you for updating the patch!

There are a few comments on v2 patch.

In compute_expr_stats(),

+		PG_CATCH();
+		{
+			ExecDropSingleTupleTableSlot(slot);
+			FreeExecutorState(estate);
+			PG_RE_THROW();
 		}

Should we switch the context to expr_context before releasing
slot and estate? Also, should we call MemoryContextDelete(expr_context)
to release palloc'ed memory in the loop?
(In fact, the error would not be cached in compute_expr_stats(), though,
 since it would be cached in make_build_data() if any.)

Should we switch to expr_context before releasing slot and estate? 
Also, should we call MemoryContextDelete(expr_context) to release
memory allocated by palloc() in the loop?

(In practice, errors would not catched in compute_expr_stats() itself,
 since they would already be caught in make_build_data() if any.)

+       /*
+        * Wrap expression evaluation and stats computation in PG_TRY so
+        * that errors from evaluating expressions (e.g. division by zero
+        * in virtual generated columns) don't cause ANALYZE to fail
+        * entirely.  Skip the statistics object and issue a WARNING
+        * instead.

How about rewriting the comments to reflect the more general case?

Extended statistics involving virtual generated columns are a somewhat
special case, while errors in expression statistics seem more common
in practice. The same applies to the commit message as well.


Regards,
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>