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Part 1: implement type narrowing and broadening.

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This commit is contained in:
Richard Newman 2017-04-03 15:02:05 -07:00
parent b117e2c463
commit 9df18e4286
1 changed files with 68 additions and 22 deletions
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90
query-algebrizer/src/clauses/mod.rs
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@ -304,28 +304,7 @@ impl ConjoiningClauses {
numeric_types.insert(ValueType::Double);
numeric_types.insert(ValueType::Long);
let entry = self.known_types.entry(variable);
match entry {
Entry::Vacant(vacant) => {
vacant.insert(numeric_types);
},
Entry::Occupied(mut occupied) => {
let narrowed: HashSet<ValueType> = numeric_types.intersection(occupied.get()).cloned().collect();
match narrowed.len() {
0 => {
// TODO: can't borrow as mutable more than once!
//self.mark_known_empty(EmptyBecause::TypeMismatch(occupied.key().clone(), occupied.get().clone(), ValueType::Double)); // I know…
},
1 => {
// Hooray!
self.extracted_types.remove(occupied.key());
},
_ => {
},
};
occupied.insert(narrowed);
},
}
self.narrow_types_for_var(variable, numeric_types);
}
/// Constrains the var if there's no existing type.
@ -355,6 +334,73 @@ impl ConjoiningClauses {
}
}
/// Like `constrain_var_to_type` but in reverse: this expands the set of types
/// with which a variable is associated.
fn broaden_types(&mut self, additional_types: BTreeMap<Variable, HashSet<ValueType>>) {
for (var, new_types) in additional_types {
match self.known_types.entry(var) {
Entry::Vacant(e) => {
if new_types.len() == 1 {
self.extracted_types.remove(e.key());
}
e.insert(new_types);
},
Entry::Occupied(mut e) => {
e.get_mut().extend(new_types.into_iter());
},
}
}
}
fn narrow_types_for_var(&mut self, var: Variable, types: HashSet<ValueType>) {
if types.is_empty() {
// We hope this never occurs; we should catch this case earlier.
self.mark_known_empty(EmptyBecause::NoValidTypes(var));
return;
}
if types.len() == 1 {
self.extracted_types.remove(&var);
}
let mut empty_because: Option<EmptyBecause> = None;
match self.known_types.entry(var) {
Entry::Vacant(e) => {
e.insert(types);
},
Entry::Occupied(mut e) => {
// TODO: we shouldn't need to clone here.
let intersected: HashSet<_> = types.intersection(e.get()).cloned().collect();
if intersected.is_empty() {
empty_because = Some(EmptyBecause::TypeMismatch(e.key().clone(),
e.get().clone(),
types.iter()
.next()
.cloned()
.unwrap()));
} else {
e.insert(intersected);
}
},
}
if let Some(e) = empty_because {
self.mark_known_empty(e);
}
}
fn narrow_types(&mut self, additional_types: BTreeMap<Variable, HashSet<ValueType>>) {
if additional_types.is_empty() {
return;
}
for (var, new_types) in additional_types {
self.narrow_types_for_var(var, new_types);
if self.is_known_empty {
return;
}
}
}
/// Ensure that the given place has the correct types to be a tx-id.
/// Right now this is mostly unimplemented: we fail hard if anything but a placeholder is
/// present.