Re: Re: Problem Observed in behavior of Create Index Concurrently and Hot Update

On 2012-11-27 10:18:37 +0530, Pavan Deolasee wrote:
> On Tue, Nov 27, 2012 at 9:01 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> > I wrote:
> >
> > Either state of indcheckxmin is valid with all three of these
> > combinations, so the specific kluge I was contemplating above doesn't
> > work. But there is no valid reason for an index to be in this state:
> >
> > indisvalid = true, indisready = false
> >
> > I suggest that to fix this for 9.2, we could abuse these flags by
> > defining that combination as meaning "ignore this index completely",
> > and having DROP INDEX CONCURRENTLY set this state during its final
> > wait before removing the index.
> >
> >
> Yeah, this looks much better, given our inability to add a new catalog
> column in 9.2. Can we cheat a little though and use a value other than 0
> and 1 for indisvalid or indisready to tell the server to interpret it
> differently ? I would assume not, but can't see a reason unless these
> values are converted to other types and back to boolean.
>
> Andres complained about the fact that many callers of RelationGetIndexList
> are probably not ready to process invalid or not-yet-ready indexes and
> suggested that those changes should be backpatched to even older releases.
> But IMO we should do that with a test case that demonstrates that there is
> indeed a bug.

I haven't yet looked deeply enough to judge whether there are actually
bugs. But I can say that the e.g. the missing indisvalid checks in
transformFkeyCheckAttrs makes me pretty uneasy. Vacuum not checking
whether indexes are ready isn't nice either.

> Also, we should teach RelationGetIndexList to take a flags
> argument and filter out indexes that the caller is not interested instead
> of every caller doing the checks separately.

Given that RelationGetIndexList currently is just returning a cached
list I don't see how thats going to work without significant overhead.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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