Re: Beta 6 Regression results on Redat 7.0. - Mailing list pgsql-hackers

The Hermit Hacker <scrappy@hub.org> writes:
> Okay, I roll'd an RC1 but haven't put it up for FTP yet ... I'll wait for
> a few hours to see if anyone can reproduce this, and, if not, put out what
> I've rolled ...

This will not be RC1 :-(

I'm been running one backend doing repeated iterations of

CREATE TABLE temptest(col int);
INSERT INTO temptest VALUES (1);

CREATE TEMP TABLE temptest(col int);
INSERT INTO temptest VALUES (2);
SELECT * FROM temptest;
DROP TABLE temptest;

SELECT * FROM temptest;
DROP TABLE temptest;

and another one doing repeated CHECKPOINTs.  I've already gotten a
couple occurrences of Lamar's failure.

I think the problem is that BufferSync unconditionally does PinBuffer
on each buffer, and holds the pin during intervals where it's released
BufMgrLock, even if there's not really anything for it to do on that
buffer.  If someone else is running FlushRelationBuffers then it's
possible for that routine to see a nonzero pin count when it looks.

Vadim, what do you think about how to change this?  I think this is
BufferSync's fault not FlushRelationBuffers's ...
        regards, tom lane