Re: remaining sql/json patches

On Thu, Sep 21, 2023 at 9:41 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> On Thu, Sep 21, 2023 at 5:58 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> > I keep looking at 0001, and in the struct definition I think putting the
> > escontext at the bottom is not great, because there's a comment a few
> > lines above that says "XXX: following fields only needed during
> > "compilation"), could be thrown away afterwards". This comment is not
> > strictly true, because innermost_caseval is actually used by
> > array_map(); yet it seems that ->escontext should appear before that
> > comment.
>
> Hmm. Actually, we can make it so that *escontext* is only needed
> during ExecInitExprRec() and never after that. I've done that in the
> attached updated patch, where you can see that ExprState.escontext is
> only ever touched in execExpr.c. Also, I noticed that I had
> forgotten to extract one more expression node type's conversion to use
> soft errors from the main patch (0003). That is CoerceToDomain, which
> I've now moved into 0001.
>
> > Also, ->escontext's own comment in ExprState seems to be saying too much
> > and not saying enough. I would reword it as "For expression nodes that
> > support soft errors. NULL if caller wants them thrown instead". The
> > shortest I could make so that it fits in a single is "For nodes that can
> > error softly. NULL if caller wants them thrown", or "For
> > soft-error-enabled nodes. NULL if caller wants errors thrown". Not
> > sure if those are good enough, or just make the comment the whole four
> > lines ...
>
> How about:
>
> + /*
> + * For expression nodes that support soft errors. Set to NULL before
> + * calling ExecInitExprRec() if the caller wants errors thrown.
> + */

Maybe the following is better:

+ /*
+ * For expression nodes that support soft errors. Should be set to NULL
+ * before calling ExecInitExprRec() if the caller wants errors thrown.
+ */

...as in the attached.

Alvaro, do you think your concern regarding escontext not being in the
right spot in the ExprState struct is addressed? It doesn't seem very
critical to me to place it in the struct's 1st cacheline, because
escontext is not accessed in performance critical paths such as during
expression evaluation, especially with the latest version. (It would
get accessed during evaluation with previous versions.)

If so, I'd like to move ahead with committing it. 0002 seems almost there too.

--
Thanks, Amit Langote
EDB: http://www.enterprisedb.com