What do the statistics look like for an example table that the index I used
vs not? Is ((instance_id)::text = 'test01'::text) rare for the tables where
an index scan is happening and common for the tables where a sequential
scan is chosen? How many rows in these tables generally?
Am 23.04.20 um 12:30 schrieb Stefan Knecht:
There's no question that this is more expensive than just reading the
95 rows from the index directly and returning them
not sure, you can play with
enable_seqscan = off
and compare the costs. What is the setting for random_page_cost ?
Regards,
Thanks Andreas,
But I don't think that that's what's happening.
Take this example line:
-> Seq Scan on snap_20200328 s_23 (cost=0.00..51.73
rows=95 width=12) (actual time=0.007..0.225 rows=95 loops=1)
Filter: ((instance_id)::text = 'test01'::text)
Am 23.04.20 um 10:13 schrieb Stefan Knecht:
Seq Scan on snap_20200225 s (cost=0.00..1.19 rows=1 width=12)
the partition is very small, so it's cheaper to scan only the table (one
block) than index + table (1 + 1 block).
Regards, Andreas
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