Re: jsonb contains behaviour weirdness

On Fri, Sep 12, 2014 at 6:40 AM, Alexander Korotkov
<aekorotkov@gmail.com> wrote:
> Even more weird :)

Agreed.

> The reason why jsonb contains behaves so is check in the beginning of
> jsonb_contains. It makes fast check of jsonb type and elements count before
> calling JsonbDeepContains.
>
> if (JB_ROOT_COUNT(val) < JB_ROOT_COUNT(tmpl) ||
> JB_ROOT_IS_OBJECT(val) != JB_ROOT_IS_OBJECT(tmpl))
> PG_RETURN_BOOL(false);
>
> It's likely that "JB_ROOT_COUNT(val) < JB_ROOT_COUNT(tmpl)" should be
> checked only for objects, not arrays. Also, should JsonbDeepContains does
> same fast check when it deals with nested objects?

I think this is due to commit 364ddc. That removed the extra step that
had arrays sorted (and then de-duped) ahead of time, which made arrays
behave like objects at the top level. I think that this sort + de-dup
step was mischaracterized as purely a performance thing (possibly by
me). Basically, JsonbDeepContains() is consistent with the previous
behavior at the top level, but not the current (inadvertently altered)
behavior. I think the fix is probably a return to the previous
behavior. I'll take a closer look.


-- 
Peter Geoghegan