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help / color / mirror / Atom feedFrom: Bo Guo <[email protected]>
To: [email protected]
Subject: Small table selection extremely slow!
Date: Tue, 14 May 2024 04:11:56 -0700
Message-ID: <CADHFRcjzJoRiPoJ_5Rf9ynetBPt0R5c4L_N_k-uja=W1+izvVg@mail.gmail.com> (raw)
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
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