Query hitting empty tables taking 48 minutes - Mailing list pgsql-general
| From | Robert Creager |
|---|---|
| Subject | Query hitting empty tables taking 48 minutes |
| Date | |
| Msg-id | 186A2F70-5953-4FE4-9586-BF3F114AF1CC@logicalchaos.org Whole thread Raw |
| Responses |
Re: Query hitting empty tables taking 48 minutes
(Adrian Klaver <adrian.klaver@aklaver.com>)
Re: Query hitting empty tables taking 48 minutes (Laurenz Albe <laurenz.albe@cybertec.at>) Re: Query hitting empty tables taking 48 minutes (Tom Lane <tgl@sss.pgh.pa.us>) |
| List | pgsql-general |
I have a system running FreeBSD 11.1-STABLE, PostgreSQL 9.6.8,Java OpenJDK 1.8.0_131, jdbc 9.3-1104-jdbc41 which is exhibiting very bizarre behavior. A query is executing against a couple of tables that have 1 and 0 records in them. ds3.job_entry has 0 rows, ds3.blob has 1 row. If I execute the query manually via command line, it executes fine. There are no other active queries, no locks. The system is idle, in our Dev Test group, so I can leave it this way for a bit of time. The general software setup is in production and I’ve seen nothing like this before. Even a system with 300M ds3.blob entries executes this query fine.
Jun 7 17:24:21 blackpearl postgres[10670]: [7737-1] db=tapesystem,user=Administrator,app=[unknown],client=127.0.0.1 LOG: duration: 2903612.206 ms execute fetch from S_2037436/C_2037437: SELECT * FROM ds3.blob WHERE EXISTS (SELECT * FROM ds3.job_entry WHERE blob_id = ds3.blob.id AND (job_id = $1))
tapesystem=# explain analyze SELECT * FROM ds3.blob WHERE EXISTS (SELECT * FROM ds3.job_entry WHERE blob_id = ds3.blob.id AND (job_id = 'b51357cd-e07a-4c87-a50b-999c347a5c71'));
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------
Nested Loop (cost=0.84..6.89 rows=1 width=77) (actual time=0.044..0.044 rows=0 loops=1)
-> Index Scan using job_entry_job_id_idx on job_entry (cost=0.42..2.44 rows=1 width=16) (actual time=0.042..0.042 rows=0 loops=1)
Index Cond: (job_id = 'b51357cd-e07a-4c87-a50b-999c347a5c71'::uuid)
-> Index Scan using blob_pkey on blob (cost=0.42..4.44 rows=1 width=77) (never executed)
Index Cond: (id = job_entry.blob_id)
Planning time: 0.388 ms
Execution time: 0.118 ms
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------
Nested Loop (cost=0.84..6.89 rows=1 width=77) (actual time=0.044..0.044 rows=0 loops=1)
-> Index Scan using job_entry_job_id_idx on job_entry (cost=0.42..2.44 rows=1 width=16) (actual time=0.042..0.042 rows=0 loops=1)
Index Cond: (job_id = 'b51357cd-e07a-4c87-a50b-999c347a5c71'::uuid)
-> Index Scan using blob_pkey on blob (cost=0.42..4.44 rows=1 width=77) (never executed)
Index Cond: (id = job_entry.blob_id)
Planning time: 0.388 ms
Execution time: 0.118 ms
| pid | client_port | runtime | query_start | datname | state | query | usename |
|---|---|---|---|---|---|---|---|
| 10670 | 11211 | 0 years 0 mons 0 days 0 hours 43 mins 28.852273 secs | 2018-06-07 17:24:22.026384 | tapesystem | active | SELECT * FROM ds3.blob WHERE EXISTS (SELECT * FROM ds3.job_entry WHERE blob_id = ds3.blob.id AND (job_id = $1)) | Administrator |
From the system with 300M ds3.blob entries, which works fine (along with every other system in house):
QUERY PLAN
Nested Loop (cost=0.57..738052.90 rows=164379 width=75) (actual time=1.001..1947.029 rows=50000 loops=1)
-> Seq Scan on job_entry (cost=0.00..10039.50 rows=164379 width=16) (actual time=0.871..56.442 rows=50000 loops=1)
Filter: (job_id = 'ef27d2fa-2727-424e-8f44-da9e33a5ca05'::uuid)
Rows Removed by Filter: 60001
-> Index Scan using blob_pkey on blob (cost=0.57..4.42 rows=1 width=75) (actual time=0.037..0.037 rows=1 loops=50000)
Index Cond: (id = job_entry.blob_id)
Planning time: 6.330 ms
Execution time: 1951.564 ms
Please keep my CC of my work e-mail present.
Best,
Robert
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