Horton

Re: new heapcheck contrib module

Tom Lane <tgl@sss.pgh.pa.us>

View thread View on postgr.es
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Peter Geoghegan <pg@bowt.ie>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>, Stephen Frost <sfrost@snowman.net>, Michael Paquier <michael@paquier.xyz>, Amul Sul <sulamul@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Andres Freund <andres@anarazel.de>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2020-10-22T20:23:36Z
Lists: pgsql-hackers 
... btw, having now looked more closely at get_xid_status(), I wonder
how come there aren't more compilers bitching about it, because it
is very very obviously broken.  In particular, the case of
requesting status for an xid that is BootstrapTransactionId or
FrozenTransactionId *will* fall through to perform
FullTransactionIdPrecedesOrEquals with an uninitialized fxid.

The fact that most compilers seem to fail to notice that is quite scary.
I suppose it has something to do with FullTransactionId being a struct,
which makes me wonder if that choice was quite as wise as we thought.

Meanwhile, so far as this code goes, I wonder why you don't just change it
to always set that value, ie

	XidBoundsViolation result;
	FullTransactionId fxid;
	FullTransactionId clog_horizon;

+	fxid = FullTransactionIdFromXidAndCtx(xid, ctx);
+
	/* Quick check for special xids */
	if (!TransactionIdIsValid(xid))
		result = XID_INVALID;
	else if (xid == BootstrapTransactionId || xid == FrozenTransactionId)
		result = XID_BOUNDS_OK;
	else
	{
		/* Check if the xid is within bounds */
-		fxid = FullTransactionIdFromXidAndCtx(xid, ctx);
		if (!fxid_in_cached_range(fxid, ctx))
		{


			regards, tom lane

Commits

  1. Add pg_amcheck, a CLI for contrib/amcheck.

  2. Refactor and generalize the ParallelSlot machinery.

  3. Generalize parallel slot result handling.

  4. Move some code from src/bin/scripts to src/fe_utils to permit reuse.

  5. Factor pattern-construction logic out of processSQLNamePattern.

  6. Doc: clean up verify_heapam() documentation.

  7. Fix more portability issues in new amcheck code.

  8. Fix portability issues in new amcheck test.

  9. Try to avoid a compiler warning about using fxid uninitialized.

  10. Extend amcheck to check heap pages.

  11. Adjust walsender usage of xlogreader, simplify APIs

  12. Improve checking of child pages in contrib/amcheck.

  13. Sanitize line pointers within contrib/amcheck.

  14. Fix possible sorting error when aborting use of abbreviated keys.