Re: A possible TODO item

On 12/31/06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> "Gurjeet Singh" <singh(dot)gurjeet(at)gmail(dot)com> writes:
> > The comment above TOAST_INDEX_HACK in tuptoaster.h is:
>
> > /*
> > * This enables de-toasting of index entries. Needed until VACUUM is
> > * smart enough to rebuild indexes from scratch.
> > */
> > #define TOAST_INDEX_HACK
>
> > Do we already have a TODO item to remove this hack? If not, I think
> there
> > should be, because it is waiting for some other progress to happen.
>
> Like what? If you want to argue that it's important to work on, you'd
> better make the case for that.

I haven't spent enough days in PGSQL-land that I can build a propaganda to
support my viewpoint.It was just an impulse I got after reading the
comments.

I thought that if the author of the code (which, now I see, is you) wanted
this hack to be removed at some point later, then it better be
documented/mentioned in TODO list, albeit at low priority, so that we don't
lose sight of it.

At first glance you might think that turning it off would Just Work,

That never crossed my mind. I haven't been able to dirty my hands enough
with backend code that I can think along those lines yet; someday I'd like
to be able to.

When searching our archives, I saw a post (
http://archives.postgresql.org/pgsql-patches/2006-07/msg00101.php)
mentioning this macro in include-files related problem, and that that
eliminating it makes btree_gist to fail.

because VACUUM should always remove index entries before removing
> heap rows, but unfortunately an index might have more copies of a key
> than just the one in the directly associated index entry. (btree,
> for example, might have copied the key into a page "high key" and/or
> boundary keys in upper tree levels. Those copies will persist long
> after the underlying row is gone.) And surely we are never going
> to make VACUUM force a complete REINDEX as the comment suggests.

In that case, can the comment be changed!

So any change in the situation is going to require considerable work
> as well as some good ideas we haven't thought of yet. Plus, it's
> unclear that values large enough to require out-of-line storage are
> reasonable candidates for indexing in the first place. So: what's
> the argument that is going to persuade everyone that this is really
> important?
>

As I said, none; just that, if it is a pending work, it should be in the
TODO list (low priority!!?), or have the comment changed, and... if this
macro is indispensable it should be removed and the the code that it
surrounds should be merged.

Best regards,

--
gurjeet[(dot)singh](at)EnterpriseDB(dot)com
singh(dot)gurjeet(at){ gmail | hotmail | yahoo }.com