Re: Question about todo item

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > I keep bugging Jan about it, since pre-7.1 and no one has come up with
> > an idea.
>
> Well, if you want an idea:
>
> BEGIN;
>
> SELECT open_toast_object(toastable_column) FROM tab WHERE ...;
>
> -- app checks that it got exactly one result back
>
> -- app lo_reads and/or lo_writes using ID returned by SELECT
>
> END;
>
> Implementation is left as an exercise for the reader ;-).
>
> Offhand this seems like it would be doable for a column-value that
> was actually moved out-of-line by TOAST, since the open_toast_object
> function could see and return the TOAST pointer, and then the read/
> write operations just hack on rows in pg_largeobject. The hard part
> is how to provide equivalent functionality (transparent to the client
> of course) when the particular value you select has *not* been moved
> out-of-line. Ideas anyone?

TOAST values aren't stored in pg_largeobject. And how do you
seek to a position in a compressed and then sliced object? We
need a way to force the object over a streaming interface
into uncompressed toast slices first. Let me think about it
for two days, Okay?

The interface lacks imho a mode (r/w/rw/a) argument. Other
than that I'd like this part.

Jan

--

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