| From: | Les <nagylzs(at)gmail(dot)com> |
|---|---|
| To: | Nick Cleaton <nick(at)cleaton(dot)net> |
| Cc: | pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Terribly slow query with very good plan? |
| Date: | 2022-02-04 10:09:52 |
| Message-ID: | CAKXe9UA_E99+E3rL45PtXR5fCkZA+ttj8o5oKAQMqmrn5c4=PA@mail.gmail.com |
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| Lists: | pgsql-performance |
> In the fast case the 'Felhasználók%' part is known at query planning
>> time, so it can be a prefix search.
>>
>> In the slow case, the planner doesn't know what that value will be, it
>> could be something that starts with '%' for example.
>>
>>
> First of all, it CANNOT start with '%'. This is a fact and this fact can
> be determined by analyzing the query. Something that the query planner
> should do, right?
>
> Second argument: the same query is also slow with the ^@ operator...
>
Oh I see, the query planner does not know that there will be no %
characters in file and folder names.
But what is the solution then? It just seems wrong that I can speed up a
query 1000 times by replacing it with a nested loop in a pl/sql function :(
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