Re: [HACKERS] path toward faster partition pruning

On 29 March 2018 at 21:35, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote:
> Beside fixing that, I have decided to get rid of the
> PartititionPruneStepOpNe (a special kind of base pruning step that was
> being used to prune list partitions using a set of <> operator clauses)
> and related functions.  Instead pruning for <> operator clauses is now
> implemented by using a combination of PartitionPruneStepOp and
> PartitionPruneStepCombine after adding a new combine op COMBINE_INVERT (I
> also renamed COMBINE_OR and COMBINE_AND to COMBINE_UNION and
> COMBINE_INTERSECT, respectively).  I decided to do so because the previous
> arrangement looked like a "hack" to support a special case that touched no
> less than quite a few places.

Hi Amit,

I've looked at the v44 patch. Thanks for making those changes.

The new not-equal handling code is not quite right.

DROP TABLE listp;
CREATE TABLE listp (a INT) PARTITION BY LIST(a);
CREATE TABLE listp1_3 PARTITION OF listp FOR VALUES IN(1,3);
CREATE TABLE listp_default PARTITION OF listp DEFAULT;

EXPLAIN SELECT * FROM listp WHERE a <> 1;
                            QUERY PLAN
------------------------------------------------------------------
 Append  (cost=0.00..54.56 rows=2537 width=4)
   ->  Seq Scan on listp1_3  (cost=0.00..41.88 rows=2537 width=4)
         Filter: (a <> 1)
(3 rows)

The default should be included here.

INSERT INTO listp VALUES(1),(2),(3);
SELECT * FROM listp WHERE a <> 1;
 a
---
 3
(1 row)

This code assumes its fine to just reverse the setting for default:

result->scan_default = !source->scan_default;

More complex handling is needed here.

I've attached a diff for a small set of other things I noticed while reviewing.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
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