| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Oleksandr Shulgin <oleksandr(dot)shulgin(at)zalando(dot)de>, Artur Zakirov <a(dot)zakirov(at)postgrespro(dot)ru>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Oleg Bartunov <obartunov(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] [PATCH] Generic type subscripting |
| Date: | 2019-05-29 16:17:09 |
| Message-ID: | CAFj8pRBhHabV06m_-n6qjmR-BQC=+t740EJs4Gu5Ck0jzNQMhQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
st 29. 5. 2019 v 17:49 odesílatel Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
napsal:
> Rebase after pg_indent. Besides, off the list there was a suggestion that
> this
> could be useful to accept more than one data type as a key for
> subscripting.
> E.g. for jsonb it probably makes sense to understand both a simple key
> name and
> jsonpath:
>
> jsonb['a'] and jsonb['$.a']
>
> While to implement it can be technically relatively straightforward I
> guess, I
> wonder if there is any opinion about how valuable it could be and what it
> should looks like from the syntax point of view (since I believe a user
> needs
> to specify which type needs to be used).
>
It is difficult decision - possibility to use jsonpath looks great, but
necessity to cast every time is not friendly.
Probably there can be preferred type if subscripting is of unknown type.
There can be similar rules to function's parameters.
so jsonb['a'] -- key
jsonb['$.a'] -- key
jsonb['$.a'::jsonpath'] -- json path
but it can be source of bad issues - so I think we don't need this feature
in this moment. This feature can be implemented later, I think.
Regards
Pavel
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