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Translate Guid.NewGuid()

See original GitHub issue

Hi. Today tried to apply .OrderBy(item => Guid.NewGuid()) to get items in random order but as I see Npgsql unable to translate it to Postgres query. In case of MsSQL it works and translates to order by newid() query. I think it will be good to have the same kind feature in Npgsql. Maybe it could be in EF.Functions, I’m not sure…

Issue Analytics

State:
Created 5 years ago
Reactions:1
Comments:11 (9 by maintainers)

Top GitHub Comments

1reaction

austindrenskicommented, Nov 13, 2018

the fact that Math.Random() is excluded by the filter means that it’s always server-evaluated, so we can translate it, can’t we?

Ope, you’re right. I had that backwards (again). We should be good to translate it.

0reactions

rojicommented, Nov 13, 2018

@austindrenski great, will look forward to your PR.

Of course you’re right - I meant System.Random(), and you’re right that it’s excluded in the filter. The explanation for that is given in https://github.com/aspnet/EntityFrameworkCore/issues/12672: if it weren’t in the filter, EF Core would evaluate it exactly once and use the same value across all rows. This is because at the moment the concept of “evaluatable” is very coarse, and more nuances are needed (evaluate on server but cache across rows, evaluate on server but don’t cache across rows…).

But to go back to the original question: the fact that Math.Random() is excluded by the filter means that it’s always server-evaluated, so we can translate it, can’t we? After all it’s logically identical to generating a random new UUID…

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