Horton

Re: [HACKERS] [PATCH] Generic type subscripting

Dmitry Dolgov <9erthalion6@gmail.com>

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From: Dmitry Dolgov <9erthalion6@gmail.com>
To: Dian M Fay <dian.m.fay@gmail.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, Alexander Korotkov <aekorotkov@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, David Steele <david@pgmasters.net>, Nikita Glukhov <n.gluhov@postgrespro.ru>, Alvaro Herrera <alvherre@2ndquadrant.com>, David Fetter <david@fetter.org>, Thomas Munro <thomas.munro@gmail.com>, Oleksandr Shulgin <oleksandr.shulgin@zalando.de>, Robert Haas <robertmhaas@gmail.com>, Michael Paquier <michael.paquier@gmail.com>, Oleg Bartunov <obartunov@gmail.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2021-01-19T14:25:14Z
Lists: pgsql-hackers

Attachments

> On Thu, Jan 14, 2021 at 12:02:42PM -0500, Dian M Fay wrote:
> > Other than that, since I've already posted the patch for returning an
> > error option, it seems that the only thing left is to decide with which
> > version to go.
>
> The trigger issue (which I did verify) makes the "no update" option
> unworkable imo, JavaScript's behavior notwithstanding. But it should be
> called out very clearly in the documentation, since it does depart from
> what people more familiar with that behavior may expect. Here's a quick
> draft, based on your v44 patch:
>
> <para>
>  <type>jsonb</type> data type supports array-style subscripting expressions
>  to extract or update particular elements. It's possible to use multiple
>  subscripting expressions to extract nested values. In this case, a chain of
>  subscripting expressions follows the same rules as the
>  <literal>path</literal> argument in <literal>jsonb_set</literal> function,
>  e.g. in case of arrays it is a 0-based operation or that negative integers
>  that appear in <literal>path</literal> count from the end of JSON arrays.
>  The result of subscripting expressions is always of the jsonb data type.
> </para>
> <para>
>  <command>UPDATE</command> statements may use subscripting in the
>  <literal>SET</literal> clause to modify <type>jsonb</type> values. Every
>  affected value must conform to the path defined by the subscript(s). If the
>  path cannot be followed to its end for any individual value (e.g.
>  <literal>val['a']['b']['c']</literal> where <literal>val['a']</literal> or
>  <literal>val['b']</literal> is null, a string, or a number), an error is
>  raised even if other values do conform.
> </para>
> <para>
>  An example of subscripting syntax:

Yes, makes sense. I've incorporated your suggestion into the last patch,
thanks.

Commits

  1. Throw error when assigning jsonb scalar instead of a composite object

  2. Filling array gaps during jsonb subscripting

  3. Implementation of subscripting for jsonb

  4. Allow ALTER TYPE to update an existing type's typsubscript value.

  5. Allow subscripting of hstore values.

  6. Support subscripting of arbitrary types, not only arrays.

  7. jit: Reference function pointer types via llvmjit_types.c.

  8. Teach contain_leaked_vars that assignment SubscriptingRefs are leaky.

  9. jit: Correct parameter type for generated expression evaluation functions.

  10. Renaming for new subscripting mechanism

  11. Fix assertion failure for SSL connections.

  12. Teach eval_const_expressions() to handle some more cases.