Hi,
Is there a way to visualize RLS policy check(s) in the query plan?
Regards,
Akash Anand
On Mon, Jul 10, 2023 at 11:33 AM Akash Anand <akash@xxxxxxxxx> wrote:
Hi,------Postgres version------postgres=# SELECT version();
version
-----------------------------------------------------------------------------------------------------------------------------------
PostgreSQL 15.3 (Debian 15.3-1.pgdg110+1) on aarch64-unknown-linux-gnu, compiled by gcc (Debian 10.2.1-6) 10.2.1 20210110, 64-bit
(1 row)------------Load data------Chinook database------------Insert dummy data into Track to bring rows count to 10 million------INSERT INTO "Track"("TrackId", "Name", "AlbumId", "MediaTypeId", "GenreId", "Milliseconds", "Bytes", "UnitPrice")
SELECT i::int, i::text, 1, 1, 1, 276349, 9056902, 0.99
FROM generate_series(3504, 10000000) AS t(i);------------Setup role and policies------create role "User";
grant select on "Album" to "User";
CREATE POLICY artist_rls_policy ON "Album" FOR SELECT TO public USING ("ArtistId"=((current_setting('rls.artistID'))::integer));
ALTER TABLE "Album" ENABLE ROW LEVEL SECURITY;
grant select on "Track" to "User";
CREATE POLICY album_rls_policy ON "Track" FOR SELECT to public
USING (
EXISTS (
select 1 from "Album" where "Track"."AlbumId" = "Album"."AlbumId"
)
);
ALTER TABLE "Track" ENABLE ROW LEVEL SECURITY;------------Query and verify the policies through psql------set role "User";
set rls.artistID = '116';
select * from "Track";------------Query plan for postgres------postgres=> explain analyze select * from "Track";
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on "Track" (cost=0.00..34589179.11 rows=2110303 width=58) (actual time=68.097..350.074 rows=14 loops=1)
Filter: (hashed SubPlan 2)
Rows Removed by Filter: 4220538
SubPlan 2
-> Index Scan using "IFK_AlbumArtistId" on "Album" (cost=0.15..8.17 rows=1 width=4) (actual time=0.017..0.018 rows=1 loops=1)
Index Cond: ("ArtistId" = (current_setting('rls.artistID'::text))::integer)
Planning Time: 0.091 ms
JIT:
Functions: 17
Options: Inlining true, Optimization true, Expressions true, Deforming true
Timing: Generation 1.008 ms, Inlining 11.450 ms, Optimization 33.233 ms, Emission 22.443 ms, Total 68.135 ms
Execution Time: 350.922 ms
(12 rows)------
------Disabled ROW LEVEL SECURITY and get appropriate tracks------QUERY PLAN
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Aggregate (cost=7657.40..7657.41 rows=1 width=32) (actual time=0.070..0.071 rows=1 loops=1)
-> Nested Loop Left Join (cost=7650.01..7657.38 rows=1 width=55) (actual time=0.061..0.068 rows=1 loops=1)
-> Seq Scan on "Album" (cost=0.00..7.34 rows=1 width=27) (actual time=0.020..0.026 rows=1 loops=1)
Filter: ("ArtistId" = 116)
Rows Removed by Filter: 346
-> Aggregate (cost=7650.01..7650.02 rows=1 width=32) (actual time=0.040..0.040 rows=1 loops=1)
-> Nested Loop (cost=0.43..6107.07 rows=102863 width=11) (actual time=0.016..0.026 rows=14 loops=1)
-> Seq Scan on "Album" "__be_0_Album" (cost=0.00..8.21 rows=1 width=4) (actual time=0.008..0.015 rows=1 loops=1)
Filter: (("AlbumId" = "Album"."AlbumId") AND ("ArtistId" = 116))
Rows Removed by Filter: 346
-> Index Scan using "IFK_TrackAlbumId" on "Track" (cost=0.43..5070.23 rows=102863 width=15) (actual time=0.008..0.009 rows=14 loops=1)
Index Cond: ("AlbumId" = "Album"."AlbumId")
SubPlan 2
-> Result (cost=0.00..0.01 rows=1 width=32) (actual time=0.000..0.000 rows=1 loops=14)
SubPlan 1
-> Result (cost=0.00..0.01 rows=1 width=32) (actual time=0.000..0.000 rows=1 loops=1)
Planning Time: 0.182 ms
Execution Time: 0.094 ms
(18 rows)------Why did Postgres choose to do a sequential scan on Track when RLS is enabled?
Regards,Akash Anand
