CODEWITHSUNDEEP
pythondatabasedjangoperformance
Ryan Saxe
Ryan Saxe

Reputation: 17829

Reasons why Django was slow

This is simply a question of curiosity. I have a script that loads a specific queryset without evaluating it, and then I print the count(). I understand that count has to go through so depending on the size it could potentially take some time, but it took over a minute to return 0 as the count of an empty queryset Why is that taking so long? is it Django or my server?

notes:

the queryset was all one type.

Upvotes: 2

Views: 459

Answers (1)

asthasr
asthasr

Reputation: 9397

It all depends on the query that you're running. If you're running a SELECT COUNT(*) FROM foo on a table that has ten rows, it's going to be very fast; but if your query involves a dozen joins, sub-selects, filters on un-indexed rows--or if the target table simply has a lot of rows--the query can take an arbitrary amount of time. In all likelihood, the bottleneck is not Django (although its ORM has some quirks), but rather the database and your query. Just because no rows meet the criteria doesn't mean that the database didn't need to deal with the other rows in the table.

Upvotes: 3

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