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From: Erik Rijkers <[email protected]>
To: Erik Wienhold <[email protected]>
To: David E. Wheeler <[email protected]>
To: [email protected]
Subject: Re: JSON Path and GIN Questions
Date: Wed, 13 Sep 2023 07:11:52 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

Op 9/13/23 om 03:00 schreef Erik Wienhold:
> Hi David,
> 
> On 13/09/2023 02:16 CEST David E. Wheeler <[email protected]> wrote:
> 
>> CREATE TABLE MOVIES (id SERIAL PRIMARY KEY, movie JSONB NOT NULL);
>> \copy movies(movie) from PROGRAM 'curl -s https://raw.githubusercontent.com/prust/wikipedia-movie-data/master/movies.json | jq -c ".[]" | sed "s|\\\\|\\\\\\\\|g"';
>> create index on movies using gin (movie);
>> analyze movies;
>>
>> I have been confused as to the difference between @@ vs @?: Why do these
>> return different results?
>>
>> david=# select id from movies where movie @@ '$ ?(@.title == "New Life Rescue")';
>>   id
>> ----
>> (0 rows)
>>
>> david=# select id from movies where movie @? '$ ?(@.title == "New Life Rescue")';
>>   id
>> ----
>>   10
>> (1 row)
>>
>> I posted this question on Stack Overflow (https://stackoverflow.com/q/77046554/79202),
>> and from the suggestion I got there, it seems that @@ expects a boolean to be
>> returned by the path query, while @? wraps it in an implicit exists(). Is that
>> right?
> 
> That's also my understanding.  We had a discussion about the docs on @@, @?, and
> jsonb_path_query on -general a while back [1].  Maybe it's useful also.
> 
>> If so, I’d like to submit a patch to the docs talking about this, and
>> suggesting the use of jsonb_path_query() to test paths to see if they return
>> a boolean or not.
> 
> +1
> 
> [1] https://www.postgresql.org/message-id/CACJufxE01sxgvtG4QEvRZPzs_roggsZeVvBSGpjM5tzE5hMCLA%40mail.gma...
> 
> --
> Erik


"All use of json*() functions preclude index usage."

That sentence is missing from the documentation.


Erik Rijkers

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