Message-ID: <640942d7-c996-0562-62c9-d69a4c1f9b1e@xs4all.nl>
Date: Wed, 13 Sep 2023 07:11:52 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.11.0
Subject: Re: JSON Path and GIN Questions
Content-Language: en-US
To: Erik Wienhold <ewie@ewie.name>, "David E. Wheeler"
 <david@justatheory.com>, pgsql-hackers@lists.postgresql.org
References: <15DD78A5-B5C4-4332-ACFE-55723259C07F@justatheory.com>
 <133696180.303713.1694566807910@office.mailbox.org>
From: Erik Rijkers <er@xs4all.nl>
In-Reply-To: <133696180.303713.1694566807910@office.mailbox.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Archived-At: <https://www.postgresql.org/message-id/640942d7-c996-0562-62c9-d69a4c1f9b1e%40xs4all.nl>
Precedence: bulk

Op 9/13/23 om 03:00 schreef Erik Wienhold:
> Hi David,
> 
> On 13/09/2023 02:16 CEST David E. Wheeler <david@justatheory.com> 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.gmail.com
> 
> --
> Erik


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

That sentence is missing from the documentation.


Erik Rijkers