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A comment on Is 20M of rows still a valid soft limit of MySQL table in 2023?. Parent comment

Re:Is 20M of rows still a valid soft limit of MySQL table in... by jl6 on Tuesday May 23, 2023 @03:12AM (#36040946)
Makes me wonder if anybody would find a SELECT APPROXIMATELY COUNT(*) useful, which would ignore the impact of current transactions.
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Re:Is 20M of rows still a valid soft limit of MySQL table in... by qeternity on Tuesday May 23, 2023 @03:18AM (#36041003)
Many DB systems have some sort of HLL function to provide a similar approximation (although I think you’re overestimating the costs that MVCC impose on large datasets).
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Re:Is 20M of rows still a valid soft limit of MySQL table in... by ddorian43 on Tuesday May 23, 2023 @07:48AM (#36042972)
Note that HLL is used for counting `unique` things. You don't need HLL for counting the rows of the table.
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Re:Is 20M of rows still a valid soft limit of MySQL table in... by 15155 on Tuesday May 23, 2023 @07:45AM (#36042948)
While not "SELECT APPROXIMATELY COUNT (*)," both MySQL and PostgreSQL both offer various metadata tables with approximate (albeit completely unfiltered) total row counts.
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Re:Is 20M of rows still a valid soft limit of MySQL table in... by newphonnewaccnt on Tuesday May 23, 2023 @09:18AM (#36043836)
I think you can use

Explain select count(*)

If you're only after a (update: really rough) rough value

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Re:Is 20M of rows still a valid soft limit of MySQL table in... by kgwxd on Tuesday May 23, 2023 @09:38AM (#36044079)
Doesn't SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED do that? Or maybe a NOLOCK hint equivalent in MySQL?
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