Re: [HACKERS] pgbench - allow to store select results into variables

I revised this patch a bit. Here's v25, where some finishing touches
are needed -- see below. I think with these changes the patch would
become committable, at least for me.

I didn't like that you were adding an #include of psqlscan_int.h into
pgbench.c, when there's a specific comment in the header saying not to
do that, so I opted for adding a new accessor function on psqlscan.h.

I renamed some of your parameter additions. I think the new names are
clearer, but they meant the +1's in your code are now in illogical
places. (I moved some; probably not enough). Please review/fix that.

I think "gset" is not a great name for the new struct member; please
find a better name. I suggest "targetvar" but feel free to choose a
name that suits your taste.

There are two XXX comments. One is about a function needing a comment
atop it. The other is about realloc behavior. To fix this one I would
add a new struct member indicating the allocated size of the array, then
growing exponentially instead of one at a time. For most cases you can
probably get away with never reallocating beyond an initial allocation
of, say, 8 members.

In the docs, the [prefix] part needs to be explained in the \cset entry;
right now it's in \gset, which comes afterwards. Let's move the
explanation up, and then in \gset say "prefix behaves as in \cset".

Thanks

--
Álvaro Herrera https://www.2ndQuadrant.com/
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