Horton

Re: POC: converting Lists into arrays

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-02-25T21:41:48Z
Lists: pgsql-hackers 
On Mon, Feb 25, 2019 at 1:31 PM Andres Freund <andres@anarazel.de> wrote:
> > 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.

But a lot of those restrictions are a consequence of needing what
amount to support functions in places as distant from pg_list.h as
pg_stat_statements.c, or the parser, or outfuncs.c. I'm not saying
that we couldn't do better here, but the design is constrained by
this. If you add a support for a new datatype, where does that leave
stored rules? Seems ticklish to me, at the very least.

-- 
Peter Geoghegan

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.