Horton

Re: [HACKERS] [PATCH] Generic type subscripting

Dmitry Dolgov <9erthalion6@gmail.com>

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From: Dmitry Dolgov <9erthalion6@gmail.com>
To: Arthur Zakirov <a.zakirov@postgrespro.ru>
Cc: Oleg Bartunov <obartunov@gmail.com>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, David Steele <david@pgmasters.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-11-15T22:02:59Z
Lists: pgsql-hackers 
> On 14 November 2017 at 22:25, Dmitry Dolgov <9erthalion6@gmail.com> wrote:
> But now I wonder if `resnull` is really needed in `jsonb_get_element`,
> `array_get_element` and it seems to me that I can even get rid of it so

On the second thought, no, looks like I'm wrong and it should be like this.
The
reason is that any `fetch` function should be in form

    (container, internal) -> extracted value

which means that we need to return an extracted value (for jsonb it's a
`jsonb`,
for array it's an `anyelement`). But at the same time in general case we can
figure out if the result is null only inside a `fetch` function,
(`jsonb_get_element` for jsonb or whatever it may be for a custom data type)
because it returns Datum. So the only way to return this information is by
reference through the `internal` argument. To summarize, If as you said it's
not that critical, I would suggest to leave it as it is.

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.