Re: [pgsql-patches] Phantom Command IDs, updated patch

Bruce Momjian wrote:
> Heikki Linnakangas wrote:
> > Here's an updated version of the phantom command ids patch.
> >
> > I found one more subtle safety issue. The array and hash table for
> > phantom command ids is dynamically grown when HeapTupleHeaderSetCmax is
> > called. Unfortunately, since HeapTupleHeaderSetCmax is used inside a
> > critical sections, running out of memory while trying to grow them would
> > cause a PANIC. That's why I moved the SetXmax/SetCmax calls outside
> > critical sections in heapam.c. I believe that's safe; if a backend
> > aborts after setting the xmax/cmax, no-one is going to care about the
> > xid of an aborted transaction in there.
> >
> > Per Tom's suggestion, I replaced the function cache code in fmgr.c and
> > similar code in plperl.c, pltcl.c, plpgsql/pl_comp.c and plpython.c to
> > use xmin+tid instead of xmin+cmin for the up-to-dateness check. I don't
> > have any tcl, perl or python test cases handy to test them, but the
> > change is small and essentially same for all of the above. Is there any
> > regression tests for the PL languages?
> >
> > I made cmin and cmax system attributes aliases for the same physical
> > commandid field. I support the idea of a complete overhaul of those
> > system attributes, but let's do that in a separate patch.
> >
> > To measure the overhead, I ran a plpgsql test case that updates a single
> > row 10000 times in a loop, generating a new phantom command id in each
> > iteration. The test took ~5% longer with the patch, so I think that's
> > acceptable. I couldn't measure a difference with pgbench (as expected).
> >
> > I think the patch is ready. Please remove the PHANTOMCID_DEBUG define
> > and ifdef blocks before applying.
>
> Heikki, I found something odd in your patch. You had an extra
> parentheses at the end of the line in the orginal and new version of the
> patch (attached). I removed it before applying, but I just wanted to
> confirm this was OK.

Huh, you already applied it?

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Alvaro Herrera http://www.CommandPrompt.com/
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