Re: Small table selection extremely slow! - Mailing list pgsql-sql

You don't elaborate on where you are seeing this "20 seconds".  Than means network, client application stuff, locking/waiting, or other things may come into play here... Please provide more info.


Bo Guo wrote on 5/14/2024 7:11 AM:

Hi,  

The following query took 20 seconds on a small table of 108 rows with a dozen columns:

SELECT * FROM azgiv.layers;

Here is the vacuum analyze result:

VACUUM (VERBOSE, ANALYZE) azgiv.layers

INFO:  vacuuming "azgiv.layers"

INFO:  table "layers": found 0 removable, 200 nonremovable row versions in 12 out of 12 pages

INFO:  vacuuming "pg_toast.pg_toast_52182"

INFO:  table "pg_toast_52182": index scan bypassed: 35 pages from table (0.69% of total) have 140 dead item identifiers

INFO:  table "pg_toast_52182": found 136 removable, 6 nonremovable row versions in 36 out of 5070 pages

INFO:  analyzing "azgiv.layers"

INFO:  "layers": scanned 12 of 12 pages, containing 200 live rows and 0 dead rows; 200 rows in sample, 200 estimated total rows

VACUUM

Here is what the explan shows:

EXPLAIN (ANALYZE, BUFFERS) SELECT * FROM azgiv.layers;

Seq Scan on layers  (cost=0.00..14.00 rows=200 width=233) (actual time=0.010..0.087 rows=200 loops=1)

  Buffers: shared hit=12

Planning:

  Buffers: shared hit=51

 Planning Time: 0.233 ms

 Execution Time: 0.121 ms

I am afraid that I have missed something obvious.  Please kindly point it out.  Many thanks!

Bo

Regards,

Michael Vitale

Michaeldba@sqlexec.com

703-600-9343