Ubuntu - `row_number() over ()` causes drastically slow query only in Production and sort of fixes itself by upgrading from version 14.8 to 15

sudoExclaimationExclaimation
August 11, 2023
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2 Answers

I have a new database with only about 225 rows.

I was facing a slow query issue only on the postgres running in production on my Ubuntu server. It was reporting 423.460 ms for the execution time. The postgres on my development Mac wasn’t having the same issue despite similar data and executed in about 1.5ms. So, I took the following steps to try to narrow down the issue.

First I checked the version of Postgres. My Mac was running Postgres 15.3 whereas my server wa running 14.8.
I also ran EXPLAIN ANALYZE on both of them and I found the slow server had a humongous cost and number of rows on the outer most Sort with sort key: Sort Key: (row_number() OVER (?)). The same query on my Mac doesn’t have this. The EXPLAIN ANALYZE of the Mac instead shows the outer most sort key as: Sort Key: o.row_number.
Also, even though my query uses things like o.kind = 'community', on the server, the EXPLAIN ANALYZE says p.kind = 'community' instead. Not sure why it’s using p instead of o and also not sure if this makes difference? My Mac on the other hand correctly references o.kind = 'community'.

Then, I upgraded my server Postgres to version 15.4 and that magically mostly fixed the issue without me making any changes to the query. The cost and number of rows for the outer most sort is still higher than my Mac. But it’s not as horrible as before. Also note that it’s still reporting the Sort Key: (row_number() OVER (?)) on the outer most sort.

My questions:

Why is the Sort Key: (row_number() OVER (?)) on the outer most sort when my query only uses row_number() over () in the second part of my WITH CTE?
Why the difference in the query between my mac and server even after upgrade?
Why would a single version upgrade fix this? A sort by row_number() OVER (?) seems fairly trivial and I feel like I haven’t yet fixed the root cause of the problem.
How can I reduce the cost and rows to get it similar to my Mac?

I would like to get to the root cause of this problem so it doesn’t come and bite me in the back in future.

EXPLAIN ANALYZE:

explain analyze with 
    u as (select r.*, case when r.kind = 'user' then 1 else 0 end as extra_sort  from records_view r  where r.kind != 'action' AND ((r.kind = 'user' AND r.author = ANY('{AUTHOR_NAME}')) OR r.original_signature = ANY('{SOME_SIGNATURE}'))),
    o as (select row_number() over (), p.* from (select * from u order by extra_sort DESC ) p),
    h as (select o.*, jsonb_strip_nulls(jsonb_build_object('author_handle',ul.handle,'community_handle',cl.handle)) as handles from o left join lookup ul on ul.sig_or_author = o.author left join lookup cl on case when o.kind = 'community' then cl.sig_or_author = o.original_signature else cl.sig_or_author = o.references_original_signature end)
    , actioned as (select h.*, case when a.record is not null then jsonb_build_object('signature',a.signature,'record',a.record) else null end as action from h left join records_view a on h.original_signature = a.references_original_signature AND a.author = 'AUTHOR_NAME' AND a.kind = 'action' AND h.kind = ANY('{community,text,user}'))
    select record, signature, author, tallies,  action, null as original_record, case when handles = '{}'::jsonb then null else handles end as handles from actioned order by row_number;

UBUNTU SERVER BEFORE UPGRADE:

SELECT VERSION();
                                                                version                                                                 
----------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 14.8 (Ubuntu 14.8-0ubuntu0.22.04.1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 11.3.0-1ubuntu1~22.04.1) 11.3.0, 64-bit
(1 row)

EXPLAIN ANALYZE OUTPUT:

Sort  (cost=1380266.29..1382702.79 rows=974600 width=959) (actual time=420.311..420.313 rows=2 loops=1)
Sort Key: (row_number() OVER (?))
Sort Method: quicksort  Memory: 29kB
->  Nested Loop Left Join  (cost=428.20..54117.14 rows=974600 width=959) (actual time=420.299..420.308 rows=2 loops=1)
      Join Filter: CASE WHEN (p.kind = 'community'::text) THEN ((cl.sig_or_author)::text = p.original_signature) ELSE ((cl.sig_or_author)::text = p.references_original_signature) END
      Rows Removed by Join Filter: 29
      ->  Merge Left Join  (cost=428.20..493.14 rows=2215 width=1976) (actual time=420.284..420.287 rows=2 loops=1)
            Merge Cond: (p.original_signature = r.references_original_signature)
            Join Filter: (p.kind = ANY ('{community,text,user}'::text[]))
            ->  Sort  (cost=203.23..204.78 rows=621 width=1293) (actual time=419.832..419.833 rows=2 loops=1)
                  Sort Key: p.original_signature
                  Sort Method: quicksort  Memory: 28kB
                  ->  Hash Left Join  (cost=144.15..174.42 rows=621 width=1293) (actual time=419.826..419.829 rows=2 loops=1)
                        Hash Cond: (p.author = (ul.sig_or_author)::text)
                        ->  WindowAgg  (cost=114.35..129.87 rows=621 width=1428) (actual time=419.812..419.815 rows=2 loops=1)
                              ->  Subquery Scan on p  (cost=114.35..122.11 rows=621 width=1253) (actual time=419.809..419.810 rows=2 loops=1)
                                    ->  Sort  (cost=114.35..115.90 rows=621 width=1420) (actual time=419.807..419.808 rows=2 loops=1)
                                          Sort Key: (CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END) DESC
                                          Sort Method: quicksort  Memory: 28kB
                                          ->  Nested Loop Left Join  (cost=0.00..85.54 rows=621 width=1420) (actual time=419.716..419.803 rows=2 loops=1)
                                                Join Filter: CASE WHEN (r_1.kind = 'user'::text) THEN (r_1.author = t_1.sig_or_author) ELSE (r_1.original_signature = t_1.sig_or_author) END
                                                Rows Removed by Join Filter: 157
                                                ->  Seq Scan on records r_1  (cost=0.00..50.95 rows=18 width=1221) (actual time=419.690..419.754 rows=2 loops=1)
                                                      Filter: (is_latest AND (kind <> 'action'::text) AND (((kind = 'user'::text) AND (author = ANY ('{AUTHOR_NAME}'::text[]))) OR (original_signature = ANY ('{SOME_SIGNATURE}'::text[]))))
                                                      Rows Removed by Filter: 221
                                                ->  Materialize  (cost=0.00..6.04 rows=69 width=411) (actual time=0.005..0.019 rows=79 loops=2)
                                                      ->  Seq Scan on tally t_1  (cost=0.00..5.69 rows=69 width=411) (actual time=0.005..0.015 rows=79 loops=1)
                        ->  Hash  (cost=18.80..18.80 rows=880 width=64) (actual time=0.008..0.008 rows=15 loops=1)
                              Buckets: 1024  Batches: 1  Memory Usage: 12kB
                              ->  Seq Scan on lookup ul  (cost=0.00..18.80 rows=880 width=64) (actual time=0.002..0.003 rows=15 loops=1)
            ->  Sort  (cost=224.97..229.45 rows=1794 width=879) (actual time=0.443..0.444 rows=51 loops=1)
                  Sort Key: r.references_original_signature
                  Sort Method: quicksort  Memory: 96kB
                  ->  Nested Loop Left Join  (cost=0.00..128.01 rows=1794 width=879) (actual time=0.022..0.409 rows=70 loops=1)
                        Join Filter: CASE WHEN (r.kind = 'user'::text) THEN (r.author = t.sig_or_author) ELSE (r.original_signature = t.sig_or_author) END
                        Rows Removed by Join Filter: 5530
                        ->  Seq Scan on records r  (cost=0.00..50.39 rows=52 width=1221) (actual time=0.002..0.036 rows=70 loops=1)
                              Filter: (is_latest AND (author = 'AUTHOR_NAME'::text) AND (kind = 'action'::text))
                              Rows Removed by Filter: 153
                        ->  Materialize  (cost=0.00..6.04 rows=69 width=196) (actual time=0.000..0.002 rows=79 loops=70)
                              ->  Seq Scan on tally t  (cost=0.00..5.69 rows=69 width=196) (actual time=0.001..0.006 rows=79 loops=1)
      ->  Materialize  (cost=0.00..23.20 rows=880 width=64) (actual time=0.000..0.002 rows=15 loops=2)
            ->  Seq Scan on lookup cl  (cost=0.00..18.80 rows=880 width=64) (actual time=0.001..0.001 rows=15 loops=1)
Planning Time: 1.177 ms
JIT:
Functions: 43
Options: Inlining true, Optimization true, Expressions true, Deforming true
Timing: Generation 3.042 ms, Inlining 9.559 ms, Optimization 266.372 ms, Emission 143.716 ms, Total 422.689 ms
Execution Time: 423.460 ms
(49 rows)

UBUNTU SERVER AFTER UPGRADE:

SELECT VERSION();
                                                              version                                                              
-----------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 15.4 (Ubuntu 15.4-1.pgdg22.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0, 64-bit
(1 row)

EXPLAIN ANALYZE OUTPUT:

Sort  (cost=11886.89..11938.75 rows=20745 width=957) (actual time=1.432..1.436 rows=2 loops=1)
Sort Key: (row_number() OVER (?))
Sort Method: quicksort  Memory: 27kB
->  Nested Loop Left Join  (cost=452.87..1677.43 rows=20745 width=957) (actual time=1.410..1.430 rows=2 loops=1)
      Join Filter: CASE WHEN (p.kind = 'community'::text) THEN ((cl.sig_or_author)::text = p.original_signature) ELSE ((cl.sig_or_author)::text = p.references_original_signature) END
      Rows Removed by Join Filter: 29
      ->  Merge Left Join  (cost=452.87..535.26 rows=2766 width=1949) (actual time=1.385..1.392 rows=2 loops=1)
            Merge Cond: (p.original_signature = r.references_original_signature)
            Join Filter: (p.kind = ANY ('{community,text,user}'::text[]))
            ->  Sort  (cost=185.16..186.84 rows=672 width=1268) (actual time=0.279..0.281 rows=2 loops=1)
                  Sort Key: p.original_signature
                  Sort Method: quicksort  Memory: 27kB
                  ->  Hash Left Join  (cost=120.85..153.61 rows=672 width=1268) (actual time=0.270..0.276 rows=2 loops=1)
                        Hash Cond: (p.author = (ul.sig_or_author)::text)
                        ->  WindowAgg  (cost=119.51..136.31 rows=672 width=1426) (actual time=0.246..0.250 rows=2 loops=1)
                              ->  Subquery Scan on p  (cost=119.51..127.91 rows=672 width=1251) (actual time=0.241..0.243 rows=2 loops=1)
                                    ->  Sort  (cost=119.51..121.19 rows=672 width=1418) (actual time=0.240..0.241 rows=2 loops=1)
                                          Sort Key: (CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END) DESC
                                          Sort Method: quicksort  Memory: 27kB
                                          ->  Nested Loop Left Join  (cost=0.00..87.95 rows=672 width=1418) (actual time=0.111..0.234 rows=2 loops=1)
                                                Join Filter: CASE WHEN (r_1.kind = 'user'::text) THEN (r_1.author = t_1.sig_or_author) ELSE (r_1.original_signature = t_1.sig_or_author) END
                                                Rows Removed by Join Filter: 157
                                                ->  Seq Scan on records r_1  (cost=0.00..50.90 rows=17 width=1219) (actual time=0.070..0.147 rows=2 loops=1)
                                                      Filter: (is_latest AND (kind <> 'action'::text) AND (((kind = 'user'::text) AND (author = ANY ('{AUTHOR_NAME}'::text[]))) OR (original_signature = ANY ('{SOME_SIGNATURE}'::text[]))))
                                                      Rows Removed by Filter: 221
                                                ->  Materialize  (cost=0.00..6.19 rows=79 width=411) (actual time=0.003..0.030 rows=79 loops=2)
                                                      ->  Seq Scan on tally t_1  (cost=0.00..5.79 rows=79 width=411) (actual time=0.003..0.018 rows=79 loops=1)
                        ->  Hash  (cost=1.15..1.15 rows=15 width=190) (actual time=0.012..0.013 rows=15 loops=1)
                              Buckets: 1024  Batches: 1  Memory Usage: 12kB
                              ->  Seq Scan on lookup ul  (cost=0.00..1.15 rows=15 width=190) (actual time=0.002..0.003 rows=15 loops=1)
            ->  Sort  (cost=267.70..273.23 rows=2212 width=877) (actual time=1.094..1.097 rows=51 loops=1)
                  Sort Key: r.references_original_signature
                  Sort Method: quicksort  Memory: 77kB
                  ->  Nested Loop Left Join  (cost=0.00..144.81 rows=2212 width=877) (actual time=0.042..1.019 rows=70 loops=1)
                        Join Filter: CASE WHEN (r.kind = 'user'::text) THEN (r.author = t.sig_or_author) ELSE (r.original_signature = t.sig_or_author) END
                        Rows Removed by Join Filter: 5530
                        ->  Seq Scan on records r  (cost=0.00..50.34 rows=56 width=1219) (actual time=0.003..0.079 rows=70 loops=1)
                              Filter: (is_latest AND (author = 'AUTHOR_NAME'::text) AND (kind = 'action'::text))
                              Rows Removed by Filter: 153
                        ->  Materialize  (cost=0.00..6.19 rows=79 width=196) (actual time=0.000..0.005 rows=79 loops=70)
                              ->  Seq Scan on tally t  (cost=0.00..5.79 rows=79 width=196) (actual time=0.001..0.011 rows=79 loops=1)
      ->  Materialize  (cost=0.00..1.22 rows=15 width=190) (actual time=0.002..0.004 rows=15 loops=2)
            ->  Seq Scan on lookup cl  (cost=0.00..1.15 rows=15 width=190) (actual time=0.001..0.003 rows=15 loops=1)
Planning Time: 1.164 ms
Execution Time: 1.508 ms
(45 rows)

HOME Mac:

SELECT VERSION();
                                                            version                                                             
--------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 15.3 (Homebrew) on x86_64-apple-darwin22.4.0, compiled by Apple clang version 14.0.3 (clang-1403.0.22.14.1), 64-bit
(1 row)

EXPLAIN ANALYZE OUTPUT:

Sort  (cost=25.08..25.10 rows=10 width=1089) (actual time=0.028..0.030 rows=0 loops=1)
   Sort Key: o.row_number
   Sort Method: quicksort  Memory: 25kB
   ->  Nested Loop Left Join  (cost=14.06..24.91 rows=10 width=1089) (actual time=0.023..0.026 rows=0 loops=1)
         Join Filter: CASE WHEN (o.kind = 'community'::text) THEN ((cl.sig_or_author)::text = o.original_signature) ELSE ((cl.sig_or_author)::text = o.references_original_signature) END
         ->  Nested Loop Left Join  (cost=14.06..23.30 rows=4 width=2216) (actual time=0.023..0.025 rows=0 loops=1)
               Join Filter: ((ul.sig_or_author)::text = o.author)
               ->  Hash Right Join  (cost=14.06..21.93 rows=4 width=2203) (actual time=0.023..0.025 rows=0 loops=1)
                     Hash Cond: (r.references_original_signature = o.original_signature)
                     Join Filter: (o.kind = ANY ('{community,text,user}'::text[]))
                     ->  Nested Loop Left Join  (cost=0.14..7.99 rows=4 width=1009) (never executed)
                           Join Filter: CASE WHEN (r.kind = 'user'::text) THEN (r.author = t.sig_or_author) ELSE (r.original_signature = t.sig_or_author) END
                           ->  Index Scan using records_author_idx on records r  (cost=0.14..6.77 rows=1 width=1350) (never executed)
                                 Index Cond: (author = 'AUTHOR_NAME'::text)
                                 Filter: (is_latest AND (kind = 'action'::text))
                           ->  Seq Scan on tally t  (cost=0.00..1.08 rows=8 width=196) (never executed)
                     ->  Hash  (cost=13.87..13.87 rows=4 width=1390) (actual time=0.016..0.017 rows=0 loops=1)
                           Buckets: 1024  Batches: 1  Memory Usage: 8kB
                           ->  Subquery Scan on o  (cost=13.73..13.87 rows=4 width=1390) (actual time=0.015..0.016 rows=0 loops=1)
                                 ->  WindowAgg  (cost=13.73..13.83 rows=4 width=1557) (actual time=0.015..0.016 rows=0 loops=1)
                                       ->  Subquery Scan on p  (cost=13.73..13.78 rows=4 width=1382) (actual time=0.014..0.015 rows=0 loops=1)
                                             ->  Sort  (cost=13.73..13.74 rows=4 width=1549) (actual time=0.014..0.015 rows=0 loops=1)
                                                   Sort Key: (CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END) DESC
                                                   Sort Method: quicksort  Memory: 25kB
                                                   ->  Nested Loop Left Join  (cost=8.42..13.69 rows=4 width=1549) (actual time=0.009..0.009 rows=0 loops=1)
                                                         Join Filter: CASE WHEN (r_1.kind = 'user'::text) THEN (r_1.author = t_1.sig_or_author) ELSE (r_1.original_signature = t_1.sig_or_author) END
                                                         ->  Bitmap Heap Scan on records r_1  (cost=8.42..12.44 rows=1 width=1350) (actual time=0.008..0.009 rows=0 loops=1)
                                                               Recheck Cond: ((author = ANY ('{AUTHOR_NAME}'::text[])) OR ((original_signature = ANY ('{SOME_SIGNATURE}'::text[])) AND is_latest))
                                                               Filter: (is_latest AND (kind <> 'action'::text) AND (((kind = 'user'::text) AND (author = ANY ('{AUTHOR_NAME}'::text[]))) OR (original_signature = ANY ('{SOME_SIGNATURE}'::text[]))))
                                                               ->  BitmapOr  (cost=8.42..8.42 rows=1 width=0) (actual time=0.008..0.008 rows=0 loops=1)
                                                                     ->  Bitmap Index Scan on records_author_idx  (cost=0.00..4.15 rows=1 width=0) (actual time=0.004..0.004 rows=0 loops=1)
                                                                           Index Cond: (author = ANY ('{AUTHOR_NAME}'::text[]))
                                                                     ->  Bitmap Index Scan on records_original_signature_idx  (cost=0.00..4.27 rows=1 width=0) (actual time=0.003..0.003 rows=0 loops=1)
                                                                           Index Cond: (original_signature = ANY ('{SOME_SIGNATURE}'::text[]))
                                                         ->  Seq Scan on tally t_1  (cost=0.00..1.08 rows=8 width=411) (never executed)
               ->  Materialize  (cost=0.00..1.07 rows=5 width=186) (never executed)
                     ->  Seq Scan on lookup ul  (cost=0.00..1.05 rows=5 width=186) (never executed)
         ->  Materialize  (cost=0.00..1.07 rows=5 width=186) (never executed)
               ->  Seq Scan on lookup cl  (cost=0.00..1.05 rows=5 width=186) (never executed)
 Planning Time: 1.578 ms
 Execution Time: 0.149 ms
(41 rows)

Answers

Chosen as BEST ANSWER

StackOverflow limits my question to 30,000 characters. So, I am adding this detail as asked by @FrankHeikens. Note that this is not the answer, it's an edit to my question:

EDIT: I no longer have access to the old version of postgres on the server. Here's the verbose output of the explain (analyze, verbose, buffers, settings) on server:

Sort Method: quicksort  Memory: 27kB
   Buffers: shared hit=113
   ->  Nested Loop Left Join  (cost=452.87..1677.43 rows=20745 width=957) (actual time=1.297..1.314 rows=2 loops=1)
         Output: p.record, p.signature, p.author, p.tallies, CASE WHEN (r.record IS NOT NULL) THEN jsonb_build_object('signature', r.signature, 'record', r.record) ELSE NULL::jsonb END, NULL::text, CASE WHEN (jsonb_strip_nulls(jsonb_build_object('author_handle', ul.handle, 'community_handle', cl.handle)) = '{}'::jsonb) THEN NULL::jsonb ELSE jsonb_strip_nulls(jsonb_build_object('author_handle', ul.handle, 'community_handle', cl.handle)) END, (row_number() OVER (?))
         Join Filter: CASE WHEN (p.kind = 'community'::text) THEN ((cl.sig_or_author)::text = p.original_signature) ELSE ((cl.sig_or_author)::text = p.references_original_signature) END
         Rows Removed by Join Filter: 29
         Buffers: shared hit=113
         ->  Merge Left Join  (cost=452.87..535.26 rows=2766 width=1949) (actual time=1.242..1.248 rows=2 loops=1)
               Output: p.record, p.signature, p.author, p.tallies, (row_number() OVER (?)), p.kind, p.original_signature, p.references_original_signature, r.record, r.signature, ul.handle
               Merge Cond: (p.original_signature = r.references_original_signature)
               Join Filter: (p.kind = ANY ('{community,text,user}'::text[]))
               Buffers: shared hit=105
               ->  Sort  (cost=185.16..186.84 rows=672 width=1268) (actual time=0.287..0.289 rows=2 loops=1)
                     Output: p.record, p.signature, p.author, p.tallies, (row_number() OVER (?)), p.kind, p.original_signature, p.references_original_signature, ul.handle
                     Sort Key: p.original_signature
                     Sort Method: quicksort  Memory: 27kB
                     Buffers: shared hit=53
                     ->  Hash Left Join  (cost=120.85..153.61 rows=672 width=1268) (actual time=0.277..0.284 rows=2 loops=1)
                           Output: p.record, p.signature, p.author, p.tallies, (row_number() OVER (?)), p.kind, p.original_signature, p.references_original_signature, ul.handle
                           Hash Cond: (p.author = (ul.sig_or_author)::text)
                           Buffers: shared hit=53
                           ->  WindowAgg  (cost=119.51..136.31 rows=672 width=1426) (actual time=0.257..0.262 rows=2 loops=1)
                                 Output: row_number() OVER (?), p.signature, p.record, p.author, NULL::timestamp with time zone, NULL::timestamp with time zone, p.original_signature, p.kind, NULL::text, NULL::text, p.references_original_signature, NULL::text, NULL::ltree, NULL::boolean, NULL::timestamp with time zone, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, p.tallies, NULL::integer
                                 Buffers: shared hit=52
                                 ->  Subquery Scan on p  (cost=119.51..127.91 rows=672 width=1251) (actual time=0.249..0.251 rows=2 loops=1)
                                       Output: p.signature, p.record, p.author, p.original_signature, p.kind, p.references_original_signature, p.tallies
                                       Buffers: shared hit=52
                                       ->  Sort  (cost=119.51..121.19 rows=672 width=1418) (actual time=0.248..0.249 rows=2 loops=1)
                                             Output: r_1.signature, r_1.record, r_1.author, NULL::timestamp with time zone, NULL::timestamp with time zone, r_1.original_signature, r_1.kind, NULL::text, NULL::text, r_1.references_original_signature, NULL::text, NULL::ltree, NULL::boolean, NULL::timestamp with time zone, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, (CASE WHEN (r_1.kind = ANY ('{community,text,user}'::text[])) THEN t_1.tallies ELSE NULL::jsonb END), (CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END)
                                             Sort Key: (CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END) DESC
                                             Sort Method: quicksort  Memory: 27kB
                                             Buffers: shared hit=52
                                             ->  Nested Loop Left Join  (cost=0.00..87.95 rows=672 width=1418) (actual time=0.111..0.244 rows=2 loops=1)
                                                   Output: r_1.signature, r_1.record, r_1.author, NULL::timestamp with time zone, NULL::timestamp with time zone, r_1.original_signature, r_1.kind, NULL::text, NULL::text, r_1.references_original_signature, NULL::text, NULL::ltree, NULL::boolean, NULL::timestamp with time zone, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, CASE WHEN (r_1.kind = ANY ('{community,text,user}'::text[])) THEN t_1.tallies ELSE NULL::jsonb END, CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END
                                                   Join Filter: CASE WHEN (r_1.kind = 'user'::text) THEN (r_1.author = t_1.sig_or_author) ELSE (r_1.original_signature = t_1.sig_or_author) END
                                                   Rows Removed by Join Filter: 157
                                                   Buffers: shared hit=52
                                                   ->  Seq Scan on public.records r_1  (cost=0.00..50.90 rows=17 width=1219) (actual time=0.073..0.156 rows=2 loops=1)
                                                         Output: r_1.signature, r_1.record, r_1.author, r_1.discovered_at, r_1.original_discovered_at, r_1.original_signature, r_1.kind, r_1.subkind, r_1.slug, r_1.references_original_signature, r_1.in_post, r_1.path, r_1.is_latest, r_1.server_discovered_at, r_1.nsfw, r_1.nsfl, r_1.regulated, r_1.political, r_1.bot, r_1.mod_nsfw, r_1.mod_nsfl, r_1.mod_regulated, r_1.mod_political, r_1.mod_bot
                                                         Filter: (r_1.is_latest AND (r_1.kind <> 'action'::text) AND (((r_1.kind = 'user'::text) AND (r_1.author = ANY ('{AUTHOR_NAME}'::text[]))) OR (r_1.original_signature = ANY ('{SOME_SIGNATURE}'::text[]))))
                                                         Rows Removed by Filter: 221
                                                         Buffers: shared hit=47
                                                   ->  Materialize  (cost=0.00..6.19 rows=79 width=411) (actual time=0.007..0.033 rows=79 loops=2)
                                                         Output: t_1.tallies, t_1.sig_or_author
                                                         Buffers: shared hit=5
                                                         ->  Seq Scan on public.tally t_1  (cost=0.00..5.79 rows=79 width=411) (actual time=0.004..0.021 rows=79 loops=1)
                                                               Output: t_1.tallies, t_1.sig_or_author
                                                               Buffers: shared hit=5
                           ->  Hash  (cost=1.15..1.15 rows=15 width=190) (actual time=0.011..0.012 rows=15 loops=1)
                                 Output: ul.handle, ul.sig_or_author
                                 Buckets: 1024  Batches: 1  Memory Usage: 12kB
                                 Buffers: shared hit=1
                                 ->  Seq Scan on public.lookup ul  (cost=0.00..1.15 rows=15 width=190) (actual time=0.002..0.003 rows=15 loops=1)
                                       Output: ul.handle, ul.sig_or_author
                                       Buffers: shared hit=1
               ->  Sort  (cost=267.70..273.23 rows=2212 width=877) (actual time=0.944..0.947 rows=51 loops=1)
                     Output: r.record, r.signature, r.references_original_signature
                     Sort Key: r.references_original_signature
                     Sort Method: quicksort  Memory: 77kB
                     Buffers: shared hit=52
                     ->  Nested Loop Left Join  (cost=0.00..144.81 rows=2212 width=877) (actual time=0.041..0.876 rows=70 loops=1)
                           Output: r.record, r.signature, r.references_original_signature
                           Join Filter: CASE WHEN (r.kind = 'user'::text) THEN (r.author = t.sig_or_author) ELSE (r.original_signature = t.sig_or_author) END
                           Rows Removed by Join Filter: 5530
                           Buffers: shared hit=52
                           ->  Seq Scan on public.records r  (cost=0.00..50.34 rows=56 width=1219) (actual time=0.002..0.064 rows=70 loops=1)
                                 Output: r.signature, r.record, r.author, r.discovered_at, r.original_discovered_at, r.original_signature, r.kind, r.subkind, r.slug, r.references_original_signature, r.in_post, r.path, r.is_latest, r.server_discovered_at, r.nsfw, r.nsfl, r.regulated, r.political, r.bot, r.mod_nsfw, r.mod_nsfl, r.mod_regulated, r.mod_political, r.mod_bot
                                 Filter: (r.is_latest AND (r.author = 'AUTHOR_NAME'::text) AND (r.kind = 'action'::text))
                                 Rows Removed by Filter: 153
                                 Buffers: shared hit=47
                           ->  Materialize  (cost=0.00..6.19 rows=79 width=196) (actual time=0.000..0.004 rows=79 loops=70)
                                 Output: t.sig_or_author
                                 Buffers: shared hit=5
                                 ->  Seq Scan on public.tally t  (cost=0.00..5.79 rows=79 width=196) (actual time=0.001..0.009 rows=79 loops=1)
                                       Output: t.sig_or_author
                                       Buffers: shared hit=5
         ->  Materialize  (cost=0.00..1.22 rows=15 width=190) (actual time=0.002..0.004 rows=15 loops=2)
               Output: cl.handle, cl.sig_or_author
               Buffers: shared hit=1
               ->  Seq Scan on public.lookup cl  (cost=0.00..1.15 rows=15 width=190) (actual time=0.002..0.003 rows=15 loops=1)
                     Output: cl.handle, cl.sig_or_author
                     Buffers: shared hit=1
 Planning:
   Buffers: shared hit=8
 Planning Time: 0.793 ms
 Execution Time: 1.395 ms
(89 rows)

On Home Mac:

Sort  (cost=25.08..25.10 rows=10 width=1089) (actual time=0.028..0.031 rows=0 loops=1)
   Output: o.record, o.signature, o.author, o.tallies, (CASE WHEN (r.record IS NOT NULL) THEN jsonb_build_object('signature', r.signature, 'record', r.record) ELSE NULL::jsonb END), NULL::text, (CASE WHEN (jsonb_strip_nulls(jsonb_build_object('author_handle', ul.handle, 'community_handle', cl.handle)) = '{}'::jsonb) THEN NULL::jsonb ELSE jsonb_strip_nulls(jsonb_build_object('author_handle', ul.handle, 'community_handle', cl.handle)) END), o.row_number
   Sort Key: o.row_number
   Sort Method: quicksort  Memory: 25kB
   Buffers: shared hit=3
   ->  Nested Loop Left Join  (cost=14.06..24.91 rows=10 width=1089) (actual time=0.024..0.027 rows=0 loops=1)
         Output: o.record, o.signature, o.author, o.tallies, CASE WHEN (r.record IS NOT NULL) THEN jsonb_build_object('signature', r.signature, 'record', r.record) ELSE NULL::jsonb END, NULL::text, CASE WHEN (jsonb_strip_nulls(jsonb_build_object('author_handle', ul.handle, 'community_handle', cl.handle)) = '{}'::jsonb) THEN NULL::jsonb ELSE jsonb_strip_nulls(jsonb_build_object('author_handle', ul.handle, 'community_handle', cl.handle)) END, o.row_number
         Join Filter: CASE WHEN (o.kind = 'community'::text) THEN ((cl.sig_or_author)::text = o.original_signature) ELSE ((cl.sig_or_author)::text = o.references_original_signature) END
         Buffers: shared hit=3
         ->  Nested Loop Left Join  (cost=14.06..23.30 rows=4 width=2216) (actual time=0.024..0.027 rows=0 loops=1)
               Output: o.record, o.signature, o.author, o.tallies, o.row_number, o.kind, o.original_signature, o.references_original_signature, r.record, r.signature, ul.handle
               Join Filter: ((ul.sig_or_author)::text = o.author)
               Buffers: shared hit=3
               ->  Hash Right Join  (cost=14.06..21.93 rows=4 width=2203) (actual time=0.024..0.026 rows=0 loops=1)
                     Output: o.record, o.signature, o.author, o.tallies, o.row_number, o.kind, o.original_signature, o.references_original_signature, r.record, r.signature
                     Hash Cond: (r.references_original_signature = o.original_signature)
                     Join Filter: (o.kind = ANY ('{community,text,user}'::text[]))
                     Buffers: shared hit=3
                     ->  Nested Loop Left Join  (cost=0.14..7.99 rows=4 width=1009) (never executed)
                           Output: r.record, r.signature, r.references_original_signature
                           Join Filter: CASE WHEN (r.kind = 'user'::text) THEN (r.author = t.sig_or_author) ELSE (r.original_signature = t.sig_or_author) END
                           ->  Index Scan using records_author_idx on public.records r  (cost=0.14..6.77 rows=1 width=1350) (never executed)
                                 Output: r.record, r.signature, r.kind, r.author, r.original_signature, r.references_original_signature
                                 Index Cond: (r.author = 'AUTHOR_NAME'::text)
                                 Filter: (r.is_latest AND (r.kind = 'action'::text))
                           ->  Seq Scan on public.tally t  (cost=0.00..1.08 rows=8 width=196) (never executed)
                                 Output: t.sig_or_author, t.tallies
                     ->  Hash  (cost=13.87..13.87 rows=4 width=1390) (actual time=0.016..0.018 rows=0 loops=1)
                           Output: o.record, o.signature, o.author, o.tallies, o.row_number, o.kind, o.original_signature, o.references_original_signature
                           Buckets: 1024  Batches: 1  Memory Usage: 8kB
                           Buffers: shared hit=3
                           ->  Subquery Scan on o  (cost=13.73..13.87 rows=4 width=1390) (actual time=0.015..0.017 rows=0 loops=1)
                                 Output: o.record, o.signature, o.author, o.tallies, o.row_number, o.kind, o.original_signature, o.references_original_signature
                                 Buffers: shared hit=3
                                 ->  WindowAgg  (cost=13.73..13.83 rows=4 width=1557) (actual time=0.015..0.016 rows=0 loops=1)
                                       Output: row_number() OVER (?), p.signature, p.record, p.author, NULL::timestamp with time zone, NULL::timestamp with time zone, p.original_signature, p.kind, NULL::text, NULL::text, p.references_original_signature, NULL::text, NULL::ltree, NULL::boolean, NULL::timestamp with time zone, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, p.tallies, NULL::integer
                                       Buffers: shared hit=3
                                       ->  Subquery Scan on p  (cost=13.73..13.78 rows=4 width=1382) (actual time=0.014..0.015 rows=0 loops=1)
                                             Output: p.signature, p.record, p.author, p.original_signature, p.kind, p.references_original_signature, p.tallies
                                             Buffers: shared hit=3
                                             ->  Sort  (cost=13.73..13.74 rows=4 width=1549) (actual time=0.014..0.015 rows=0 loops=1)
                                                   Output: r_1.signature, r_1.record, r_1.author, NULL::timestamp with time zone, NULL::timestamp with time zone, r_1.original_signature, r_1.kind, NULL::text, NULL::text, r_1.references_original_signature, NULL::text, NULL::ltree, NULL::boolean, NULL::timestamp with time zone, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, (CASE WHEN (r_1.kind = ANY ('{community,text,user}'::text[])) THEN t_1.tallies ELSE NULL::jsonb END), (CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END)
                                                   Sort Key: (CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END) DESC
                                                   Sort Method: quicksort  Memory: 25kB
                                                   Buffers: shared hit=3
                                                   ->  Nested Loop Left Join  (cost=8.42..13.69 rows=4 width=1549) (actual time=0.010..0.011 rows=0 loops=1)
                                                         Output: r_1.signature, r_1.record, r_1.author, NULL::timestamp with time zone, NULL::timestamp with time zone, r_1.original_signature, r_1.kind, NULL::text, NULL::text, r_1.references_original_signature, NULL::text, NULL::ltree, NULL::boolean, NULL::timestamp with time zone, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, NULL::boolean, CASE WHEN (r_1.kind = ANY ('{community,text,user}'::text[])) THEN t_1.tallies ELSE NULL::jsonb END, CASE WHEN (r_1.kind = 'user'::text) THEN 1 ELSE 0 END
                                                         Join Filter: CASE WHEN (r_1.kind = 'user'::text) THEN (r_1.author = t_1.sig_or_author) ELSE (r_1.original_signature = t_1.sig_or_author) END
                                                         Buffers: shared hit=3
                                                         ->  Bitmap Heap Scan on public.records r_1  (cost=8.42..12.44 rows=1 width=1350) (actual time=0.009..0.010 rows=0 loops=1)
                                                               Output: r_1.signature, r_1.record, r_1.author, r_1.original_signature, r_1.kind, r_1.references_original_signature
                                                               Recheck Cond: ((r_1.author = ANY ('{AUTHOR_NAME}'::text[])) OR ((r_1.original_signature = ANY ('{SOME_SIGNATURE}'::text[])) AND r_1.is_latest))
                                                               Filter: (r_1.is_latest AND (r_1.kind <> 'action'::text) AND (((r_1.kind = 'user'::text) AND (r_1.author = ANY ('{AUTHOR_NAME}'::text[]))) OR (r_1.original_signature = ANY ('{SOME_SIGNATURE}'::text[]))))
                                                               Buffers: shared hit=3
                                                               ->  BitmapOr  (cost=8.42..8.42 rows=1 width=0) (actual time=0.009..0.009 rows=0 loops=1)
                                                                     Buffers: shared hit=3
                                                                     ->  Bitmap Index Scan on records_author_idx  (cost=0.00..4.15 rows=1 width=0) (actual time=0.004..0.004 rows=0 loops=1)
                                                                           Index Cond: (r_1.author = ANY ('{AUTHOR_NAME}'::text[]))
                                                                           Buffers: shared hit=1
                                                                     ->  Bitmap Index Scan on records_original_signature_idx  (cost=0.00..4.27 rows=1 width=0) (actual time=0.004..0.004 rows=0 loops=1)
                                                                           Index Cond: (r_1.original_signature = ANY ('{SOME_SIGNATURE}'::text[]))
                                                                           Buffers: shared hit=2
                                                         ->  Seq Scan on public.tally t_1  (cost=0.00..1.08 rows=8 width=411) (never executed)
                                                               Output: t_1.sig_or_author, t_1.tallies
               ->  Materialize  (cost=0.00..1.07 rows=5 width=186) (never executed)
                     Output: ul.handle, ul.sig_or_author
                     ->  Seq Scan on public.lookup ul  (cost=0.00..1.05 rows=5 width=186) (never executed)
                           Output: ul.handle, ul.sig_or_author
         ->  Materialize  (cost=0.00..1.07 rows=5 width=186) (never executed)
               Output: cl.handle, cl.sig_or_author
               ->  Seq Scan on public.lookup cl  (cost=0.00..1.05 rows=5 width=186) (never executed)
                     Output: cl.handle, cl.sig_or_author
 Planning:
   Buffers: shared hit=6
 Planning Time: 1.192 ms
 Execution Time: 0.162 ms
(76 rows)

(Edit)

- ErwinBrandstetter
- August 11, 2023 at 8:26 am
- 0 votes
0
Picking one question to answer:

"3. Why would a single version upgrade fix this? A sort by row_number() OVER (?) seems fairly trivial … "

Because Postgres 15 added a performance optimization for this case exactly. The release notes:

Improve the performance of window functions that use row_number(), rank(), dense_rank() and count() (David Rowley)

Postgres 16 has another major improvement for row_number(). The release notes:

Allow window functions to use ROWS mode internally when RANGE mode is specified but unnecessary (David Rowley)

Most prominently, this speeds up row_number(). It started all here:
- Find first 3 orders for each customer
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Ubuntu – `row_number() over ()` causes drastically slow query only in Production and sort of fixes itself by upgrading from version 14.8 to 15

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