VTab BestIndex sets .omit when Used=true #1080
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cheezypoofs
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Aug 31, 2022
The virtual table omit flag is idenfified by sqlite as an optional hint you can give the database about whether you are processed the constraints, but the library doesn't require that you actually do the filtering. Separting the .Used flag, which tells this go wrapper to setup arguments to receive the constraints in Filter, from the Omit flag allows us to inspect and perhaps do a best-effort filtering and still allow sqlite proper to complete the evaluation by leaving .omit false.
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https://github.com/mattn/go-sqlite3/blob/master/sqlite3_opt_vtable.go#L467
I'm willing to submit a PR, but wanted to first see if this was viewed as a misinterpretation of the documentation. I got the impression that setting .omit is only for specifying that you will take care of the constraint and you're hinting to sqlite that it can skip the step if it wants.
From: sqlite
I guess I was hoping that one could set
.Used = truein order to get hints and receive the right-side values inFilter(), but implement a best-effort filter and not a definite filter.Would we be open to changing the behavior here to say that
.Used = truejust means you want to use the constraint and you can still receive it in filter, and we can add a separate.Omit = trueto be more explicit about the omit? Or maybe to preserve backward compat with existing behavior we can add something like.UsedNoOmit = true.Thoughts?
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