Horton

Re: [HACKERS] [PATCH] Generic type subscripting

David Fetter <david@fetter.org>

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From: David Fetter <david@fetter.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>, Andres Freund <andres@anarazel.de>, Pavel Stehule <pavel.stehule@gmail.com>, 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>, 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: 2020-12-10T16:15:12Z
Lists: pgsql-hackers 
On Wed, Dec 09, 2020 at 12:49:48PM -0500, Tom Lane wrote:
> I've pushed the core patch now.  The jsonb parts now have to be
> rebased onto this design, which I'm assuming Dmitry will tackle
> (I do not intend to).  It's not quite clear to me whether we have
> a meeting of the minds on what the jsonb functionality should be,
> anyway.  Alexander seemed to be thinking about offering an option
> to let the subscript be a jsonpath, but how would we distinguish
> that from a plain-text field name?
> 
> BTW, while reviewing the thread to write the commit message,
> I was reminded of my concerns around the "is it a container"
> business.  As things stand, if type A has a typelem link to
> type B, then the system supposes that A contains B physically;
> this has implications for what's allowed in DDL, for example
> (cf find_composite_type_dependencies() and other places).
> We now have a feature whereby subscripting can yield a type
> that is not contained in the source type in that sense.
> I'd be happier if the "container" terminology were reserved for
> that sort of physical containment, which means that I think a lot
> of the commentary around SubscriptingRef is misleading.  But I do
> not have a better word to suggest offhand.  Thoughts?

Would this be something more along the lines of a "dependent type," or
is that adding too much baggage?

Best,
David.
-- 
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778

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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.