On 4/3/23 09:21, Erik Wienhold wrote:
On 03/04/2023 17:36 CEST Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote:
On 4/3/23 08:11, Erik Wienhold wrote:
On 02/04/2023 17:40 CEST Adrian Klaver <adrian.klaver@xxxxxxxxxxx> 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."
So basically a variation of jsonb @? jsonpath that returns NULL instead
of false when confused:
select '{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ == "test")' ;
?column?
----------
f
select '{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] == "test"' ;
?column?
----------
NULL
Otherwise it does the same thing:
select '{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ > 2)' ;
?column?
----------
t
select '{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] > 2' ;
?column?
----------
t
--
Erik
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
