I need to extract a small amount of data,
but the table is very large and has many indexed columns,
which makes the response time too slow

but, i do’nt want create new index.
because, table is not mine

Env

PostgreSQL 13 AWS RDS

Question

if PostgreSQL supports Index Scan DESC operations.
can i use it?

My expectation is that this query could be faster if it used an Index Scan Desc and Index Skip Scan

Query

SELECT
billingYearMonth AS billingYearMonth
, customerId       AS customerId
, childCustomerId  AS childCustomerId
, deptCustomerId   AS deptCustomerId
, cloudSupplyCode  AS cloudSupplyCode
, sum(usage) AS USAGE
FROM
bill_big_table A
WHERE
billingYearMonth     = '202407'
AND cloudSupplyCode  = '05'
AND KEYSORTORDER     = 3
GROUP BY
billingYearMonth
, customerId
, childCustomerId
, deptCustomerId
, cloudSupplyCode
ORDER BY
  billingYearMonth
, customerId
, childCustomerId
, deptCustomerId
, cloudSupplyCode 
OFFSET   0 ROWS
FETCH NEXT 1000 ROWS ONLY

Index columns (Normal)

raw DATA

INVOICEYM = ‘202407’

Table rows 339,172,200
Disk Space 412G
Rel Size 189G

EXPLAIN PLAN

Limit  (cost=0.95..106420.59 rows=1000 width=42) (actual time=11842.405..1695652.907 rows=16 loops=1)
  Output: billingyearmonth, customerid, childcustomerid, deptcustomerid, cloudsupplycode, (sum(usage))
  Buffers: shared hit=78 read=1637059
  I/O Timings: read=3288604.358
  ->  GroupAggregate  (cost=0.95..7681370.57 rows=72180 width=42) (actual time=11842.403..1695652.889 rows=16 loops=1)
        Output: billingyearmonth, customerid, childcustomerid, deptcustomerid, cloudsupplycode, sum(usage)
        Group Key: a.billingyearmonth, a.customerid, a.childcustomerid, a.deptcustomerid, a.cloudsupplycode
        Buffers: shared hit=78 read=1637059
        I/O Timings: read=3288604.358
        ->  Index Scan using bill_big_table_pkey on public.bill_big_table a  (cost=0.95..7679565.03 rows=72249 width=42) (actual time=6203.945..1695652.135 rows=828 loops=1)
              Output: billingyearmonth, customerid, childcustomerid, deptcustomerid, cloudsupplyinvoiceid, cloudsupplyinvoiceitemid, cloudsupplyinvoicetype, keybillingitemid, keysortorder, categorycode, cloudsupplycode, categoryname, itemname, pricecurrency, originamount, exchangerate, exchangeratedate, totalkrwamount, billingtype, startdate, enddate, orderuserid, productcode, usage, usageunit, startdate_l, enddate_l, billingentity, tagresourceid, meteringtype
              Index Cond: (((a.billingyearmonth)::text = '202407'::text) AND (a.keysortorder = 3) AND (a.cloudsupplycode = '05'::bpchar))
              Buffers: shared hit=78 read=1637059
              I/O Timings: read=3288604.358
Planning:
  Buffers: shared hit=122 read=12
  I/O Timings: read=11.781
Planning Time: 13.274 ms
Execution Time: 1695653.003 ms