Re: Small table selection extremely slow!

What is the table definition?

/d+

Shane Borden

sborden76(at)gmail(dot)com

Sent from my iPhone

On May 14, 2024, at 7:50 AM, Bo Guo <bo(dot)guo(at)gisticinc(dot)com> wrote:



I am using pgAdmin 4





Version


8.5




Application Mode


Server




Current User


pgadmin(at)linearbench(dot)com




Browser


Firefox 125.0




Operating System


Linux-5.15.143-1-pve-x86_64-with-glibc2.35





The performance is 0.16 ms when 

SELECT gly_id, gly_name FROM azgiv.layers;

We do not experience any slowness on other much larger tables with SELECT * FROM OtherTable;

Bo

On Tue, May 14, 2024 at 4:26 AM MichaelDBA <MichaelDBA(at)sqlexec(dot)com> wrote:

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(at)sqlexec(dot)com

703-600-9343
 

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