Horton

Re: POC: converting Lists into arrays

David Rowley <david.rowley@2ndquadrant.com>

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From: David Rowley <david.rowley@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Jesper Pedersen <jesper.pedersen@redhat.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-08-09T00:41:15Z
Lists: pgsql-hackers 
On Fri, 9 Aug 2019 at 04:24, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I wrote:
> > Perhaps there's an argument for doing something to change the behavior
> > of list_union and list_difference and friends.  Not sure --- it could
> > be a foot-gun for back-patching.  I'm already worried about the risk
> > of back-patching code that assumes the new semantics of list_concat.
> > (Which might be a good argument for renaming it to something else?
> > Just not list_union, please.)
>
> Has anyone got further thoughts about naming around list_concat
> and friends?
>
> If not, I'm inclined to go ahead with the concat-improvement patch as
> proposed in [1], modulo the one improvement David spotted.
>
>                         regards, tom lane
>
> [1] https://www.postgresql.org/message-id/6704.1563739305@sss.pgh.pa.us

I'm okay with the patch once that one improvement is done.

I think if we want to think about freeing the 2nd input List then we
can do that in another commit. Removing the redundant list_copy()
calls seems quite separate from that.

--
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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.