Re: POC, WIP: OR-clause support for indexes - Mailing list pgsql-hackers

On Wed, Jan 31, 2024 at 10:55 AM jian he <jian.universality@gmail.com> wrote:

based on my understanding of
https://www.postgresql.org/docs/current/xoper-optimization.html#XOPER-COMMUTATOR
I think you need move commutator check right after the `if
(get_op_rettype(opno) != BOOLOID)` branch

I was wrong about this part. sorry for the noise.


I have made some changes (attachment).
* if the operator expression left or right side type category is
{array | domain | composite}, then don't do the transformation.
(i am not 10% sure with composite)

To be honest, I'm not sure about this check, because we check the type of variable there:if (!IsA(orqual, OpExpr))
        {
            or_list = lappend(or_list, orqual);
            continue;
        }
And below:
if (IsA(leftop, Const))
        {
            opno = get_commutator(opno);

            if (!OidIsValid(opno))
            {
                /* Commuter doesn't exist, we can't reverse the order */
                or_list = lappend(or_list, orqual);
                continue;
            }

            nconst_expr = get_rightop(orqual);
            const_expr = get_leftop(orqual);
        }
        else if (IsA(rightop, Const))
        {
            const_expr = get_rightop(orqual);
            nconst_expr = get_leftop(orqual);
        }
        else
        {
            or_list = lappend(or_list, orqual);
            continue;
        }

Isn't that enough?

Besides, some of examples (with ARRAY) works fine:

postgres=# CREATE TABLE sal_emp (
    pay_by_quarter  integer[],
    pay_by_quater1 integer[]
);
CREATE TABLE
postgres=# INSERT INTO sal_emp
    VALUES (       
    '{10000, 10000, 10000, 10000}',
    '{1,2,3,4}');
INSERT 0 1
postgres=# select * from sal_emp where pay_by_quarter[1] = 10000 or pay_by_quarter[1]=2;
      pay_by_quarter       | pay_by_quater1
---------------------------+----------------
 {10000,10000,10000,10000} | {1,2,3,4}
(1 row)

postgres=# explain select * from sal_emp where pay_by_quarter[1] = 10000 or pay_by_quarter[1]=2;
                          QUERY PLAN                          
--------------------------------------------------------------
 Seq Scan on sal_emp  (cost=0.00..21.00 rows=9 width=64)
   Filter: (pay_by_quarter[1] = ANY ('{10000,2}'::integer[]))
(2 rows)

* if the left side of the operator expression node contains volatile
functions, then don't do the transformation.

I'm also not sure about the volatility check function, because we perform such a conversion at the parsing stage, and at this stage we don't have a RelOptInfo variable and especially a RestictInfo such as PathTarget.

Speaking of NextValueExpr, I couldn't find any examples where the current patch wouldn't work. I wrote one of them below:

postgres=# create table foo (f1 int, f2 int generated always as identity);
CREATE TABLE
postgres=# insert into foo values(1);
INSERT 0 1

postgres=# explain verbose update foo set f1 = 2 where f1=1 or f1=2 ;
                            QUERY PLAN                             
-------------------------------------------------------------------
 Update on public.foo  (cost=0.00..38.25 rows=0 width=0)
   ->  Seq Scan on public.foo  (cost=0.00..38.25 rows=23 width=10)
         Output: 2, ctid
         Filter: (foo.f1 = ANY ('{1,2}'::integer[]))
(4 rows)

Maybe I missed something. Do you have any examples?

* some other minor  cosmetic changes.

-- 
Regards,
Alena Rybakina
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company