Horton

Re: [HACKERS] [PATCH] Generic type subscripting

Chapman Flack <chap@anastigmatix.net>

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From: Chapman Flack <chap@anastigmatix.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2020-12-17T22:03:03Z
Lists: pgsql-hackers 
On 12/17/20 16:56, Chapman Flack wrote:
>> that, it's called a cast.
> 
> I find them different; XQuery was the first language I had encountered
> that provides both (a cast in XQuery is spelled 'cast as', just as you'd
> expect), and the idea of an explicit operation that means "I am only
> asserting statically what type this will have at run time; do not ever
> perform any conversion or coercion, just give me an error if I'm wrong"
> seems to be a distinct and useful one.

I should have added: it may be an idea that never seemed important in
languages that mean to statically type everything, but it seems to arise
quite naturally for a language like XQuery (and arguably jsonpath) that
tries to do a useful amount of static typing while applied to data
structures like XML or JSON that don't come with ironclad guarantees.

Regards,
-Chap

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.