Add a function for SQL EXISTS expressions.
#534
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killercup
approved these changes
Dec 8, 2016
| use result::QueryResult; | ||
| use types::Bool; | ||
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| /// Creates a SQL `EXISTS` expression. The argument must be a complete SQL |
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Start new paragraph after first sentence for nice looking docs :)
| /// usefulness. | ||
| /// | ||
| /// # Example | ||
| /// ```rust |
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| fn collect_binds(&self, out: &mut DB::BindCollector) -> QueryResult<()> { | ||
| try!(self.0.collect_binds(out)); | ||
| Ok(()) |
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Doesn't the inner self.0.collect_binds(out) suffice here without the try and Ok unit stuff?
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Yes, but I quite frequently end up adding fields to these things, so I've been consistently writing it like this (and never relying on the return value of the last delegating line) to make it easier to add more fields in the future with less diff noise
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Good point. I appreciate les diff noise :)
While this is useful for some cases where you don't want to load the rows, this won't fill every use case for the expression, as right now you wouldn't be able to build a query that references the outer table. For us to do that and have it be type safe we'd need overlapping impls for `SelectableExpression` (story of my life), which requires rust-lang/rust#29864 being implemented. Fixes #414.
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While this is useful for some cases where you don't want to load the
rows, this won't fill every use case for the expression, as right now
you wouldn't be able to build a query that references the outer table.
For us to do that and have it be type safe we'd need overlapping impls
for
SelectableExpression(story of my life), which requiresrust-lang/rust#29864 being implemented.
Fixes #414.