On Tue, Apr 4, 2023 at 12:22 AM Erik Wienhold <e...@ewie.name> wrote:
> > On 03/04/2023 17:36 CEST Adrian Klaver <adrian.kla...@aklaver.com> > wrote: > > > > On 4/3/23 08:11, Erik Wienhold wrote: > > >> On 02/04/2023 17:40 CEST Adrian Klaver <adrian.kla...@aklaver.com> > wrote: > > >> > > >> That is a long way from: > > >> > > >> jsonb @@ jsonpath → boolean > > >> > > >> Returns the result of a JSON path predicate check for the specified > JSON > > >> value. Only the first item of the result is taken into account. If the > > >> result is not Boolean, then NULL is returned. > > > > > > What do you mean? I responded to the OP's question. It's not a > suggestion > > > to update the docs. Obviously it's quite a mouthful and needs to be > boiled > > > down for the docs. Any suggestions? > > > > For me I don't see how: > > > > Predicates have existence semantics, because their operands are item > > sequences. Pairs of items from the left and right operand's sequences > > are checked. TRUE returned only if any pair satisfying the condition is > > found. In strict mode, even if the desired pair has already been found, > > all pairs still need to be examined to check the absence of errors. If > > any error occurs, UNKNOWN (analogous to SQL NULL) is returned. > > > > resolves to : > > > > Only the first item of the result is taken into account. > > > > In other words reconciling "TRUE returned only if any pair satisfying > > the condition is found." and "...first item of the result..." > > I see. > > Thinking about it now, I believe that "first item of the result" is > redundant > (and causing the OP's confusion) because the path predicate produces only a > single item: true, false, or null. That's what I wanted to show with the > first > two jsonb_path_query examples in my initial response, where the second > example > returns multiple items. > > I think the gist of @@ and json_path_match is: > > "Returns true if any JSON value at the given path matches the predicate. > Returns NULL when not a path predicate or comparing different types." > > -- > Erik > > > "Returns true if any JSON value at the given path matches the predicate. > Returns NULL when not a path predicate or comparing different types." > in first sentence, should we add something "otherwise return false." ? also, should it be "Return true"? (since only one value returned)?
