Proposal: Database Engine for D

[Jacob Carlborg via Digitalmars-d]

On 2016-01-02 21:47, Chris Wright wrote:

> So you want to create the following query:
>
>    people.filter!(x => x.surname == "Slughorn");
>
> And you've got ten million people in the collection, and you want this
> query to finish soonish. So you need to use an index. But a full index
> scan isn't so great; you want to do an index lookup if possible.
>
> That's simple enough; we generate proxy types to record what properties
> you're using and what operations you're performing. PersonProxy records
> that you're accessing a field 'surname', gives a StringFieldProxy, and
> that records that you're checking for equality with the string "Slughorn".
> The lambda returns true when opEquals returns true.
>
> But people write queries that are more complex than that, like:
>
>    people.filter!(x => x.surname == "Slughorn" || x.age <= 17);
>
> First time you run this, x.surname.opEquals("Slughorn") returns true and
> the expression as a whole returns true. You missed the second part of the
> expression. That's bad.

If D had better operator overloading or supported AST macros, opEquals 
would not return true. It would return a new proxy that overloads the || 
operator. The rest of the post falls apart from this mistake.


-- 
/Jacob Carlborg