Horton

Re: POC: converting Lists into arrays

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-02-25T21:31:31Z
Lists: pgsql-hackers 
Hi,

On 2019-02-25 13:21:30 -0800, Peter Geoghegan wrote:
> ISTM that we should separate the question of whether or not the List
> API needs to continue to work without needing to change code in third
> party extensions from the question of whether or not the List API
> needs to be replaced whole cloth. These are not exactly independent
> questions, but they don't necessarily need to be discussed all at
> once.

I'm not convinced by that - if we are happy with the list API, not
duplicating code would be a stronger argument than if we actually are
unhappy.  It makes no sense to go around and replace the same code twice
in a row if we also think other changes should be made (at the same
time, we obviously ought not to do too much at once, otherwise we'll
never get anywhere).


> Andres said that he doesn't like the pg_list.h API. It's not pretty,
> but is it really that bad?

Yes. The function names alone confound anybody new to postgres, we tend
to forget that after a few years. A lot of the function return types are
basically unpredictable without reading the code, the number of builtin
types is pretty restrictive, and there's no typesafety around the choice
of actually stored.

Greetings,

Andres Freund

Commits

  1. Remove EState.es_range_table_array.

  2. Rationalize use of list_concat + list_copy combinations.

  3. Cosmetic improvements in setup of planner's per-RTE arrays.

  4. Make better use of the new List implementation in a couple of places

  5. Fix sepgsql test results for commit d97b714a2.

  6. Avoid using lcons and list_delete_first where it's easy to do so.

  7. Remove lappend_cell...() family of List functions.

  8. Clean up some ad-hoc code for sorting and de-duplicating Lists.

  9. Redesign the API for list sorting (list_qsort becomes list_sort).

  10. Remove dead code.

  11. Represent Lists as expansible arrays, not chains of cons-cells.

  12. Standardize some more loops that chase down parallel lists.

  13. Reimplement the linked list data structure used throughout the backend.