1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
#[cfg(feature = "accumulator")]
use crate::accumulator::accumulated_map::InputAccumulatedValues;
use crate::active_query::CompletedQuery;
use crate::function::memo::Memo;
use crate::function::{Configuration, IngredientImpl};
use crate::revision::AtomicRevision;
use crate::sync::atomic::AtomicBool;
use crate::tracked_struct::TrackedStructInDb;
use crate::zalsa::{Zalsa, ZalsaDatabase};
use crate::zalsa_local::{QueryOrigin, QueryOriginRef, QueryRevisions, QueryRevisionsExtra};
use crate::{DatabaseKeyIndex, Id};
impl<C> IngredientImpl<C>
where
C: Configuration,
{
/// Specify the value for `key` *and* record that we did so.
/// Used for explicit calls to `specify`, but not needed for pre-declared tracked struct fields.
pub fn specify_and_record<'db>(&'db self, db: &'db C::DbView, key: Id, value: C::Output<'db>)
where
C::Input<'db>: TrackedStructInDb,
{
let (zalsa, zalsa_local) = db.zalsas();
let (active_query_key, current_deps) = match zalsa_local.active_query() {
Some(v) => v,
None => panic!("can only use `specify` inside a tracked function"),
};
// `specify` only works if the key is a tracked struct created in the current query.
//
// The reason is this. We want to ensure that the same result is reached regardless of
// the "path" that the user takes through the execution graph.
// If you permit values to be specified from other queries, you can have a situation like this:
// * Q0 creates the tracked struct T0
// * Q1 specifies the value for F(T0)
// * Q2 invokes F(T0)
// * Q3 invokes Q1 and then Q2
// * Q4 invokes Q2 and then Q1
//
// Now, if We invoke Q3 first, We get one result for Q2, but if We invoke Q4 first, We get a different value. That's no good.
let database_key_index = <C::Input<'db>>::database_key_index(zalsa, key);
if !zalsa_local.is_tracked_struct_of_active_query(database_key_index) {
panic!("can only use `specify` on salsa structs created during the current tracked fn");
}
// Subtle: we treat the "input" to a set query as if it were
// volatile.
//
// The idea is this. You have the current query C that
// created the entity E, and it is setting the value F(E) of the function F.
// When some other query R reads the field F(E), in order to have obtained
// the entity E, it has to have executed the query C.
//
// This will have forced C to either:
//
// - not create E this time, in which case R shouldn't have it (some kind of leak has occurred)
// - assign a value to F(E), in which case `verified_at` will be the current revision and `changed_at` will be updated appropriately
// - NOT assign a value to F(E), in which case we need to re-execute the function (which typically panics).
//
// So, ruling out the case of a leak having occurred, that means that the reader R will either see:
//
// - a result that is verified in the current revision, because it was set, which will use the set value
// - a result that is NOT verified and has untracked inputs, which will re-execute (and likely panic)
let revision = zalsa.current_revision();
let mut completed_query = CompletedQuery {
revisions: QueryRevisions {
changed_at: current_deps.changed_at,
durability: current_deps.durability,
origin: QueryOrigin::assigned(active_query_key),
#[cfg(feature = "accumulator")]
accumulated_inputs: Default::default(),
verified_final: AtomicBool::new(true),
extra: QueryRevisionsExtra::default(),
},
stale_tracked_structs: Vec::new(),
};
let memo_ingredient_index = self.memo_ingredient_index(zalsa, key);
if let Some(old_memo) = self.get_memo_from_table_for(zalsa, key, memo_ingredient_index) {
self.backdate_if_appropriate(
old_memo,
database_key_index,
&mut completed_query.revisions,
&value,
);
self.diff_outputs(zalsa, database_key_index, old_memo, &completed_query);
}
let memo = Memo {
value: Some(value),
verified_at: AtomicRevision::from(revision),
revisions: completed_query.revisions,
};
crate::tracing::debug!(
"specify: about to add memo {:#?} for key {:?}",
memo.tracing_debug(),
key
);
self.insert_memo(zalsa, key, memo, memo_ingredient_index);
// Record that the current query *specified* a value for this cell.
let database_key_index = self.database_key_index(key);
zalsa_local.add_output(database_key_index);
}
/// Invoked when the query `executor` has been validated as having green inputs
/// and `key` is a value that was specified by `executor`.
/// Marks `key` as valid in the current revision since if `executor` had re-executed,
/// it would have specified `key` again.
pub(super) fn validate_specified_value(
&self,
zalsa: &Zalsa,
executor: DatabaseKeyIndex,
key: Id,
) {
let memo_ingredient_index = self.memo_ingredient_index(zalsa, key);
let memo = match self.get_memo_from_table_for(zalsa, key, memo_ingredient_index) {
Some(m) => m,
None => return,
};
// If we are marking this as validated, it must be a value that was
// assigned by `executor`.
match memo.revisions.origin.as_ref() {
QueryOriginRef::Assigned(by_query) => assert_eq!(by_query, executor),
_ => panic!(
"expected a query assigned by `{:?}`, not `{:?}`",
executor, memo.revisions.origin,
),
}
let database_key_index = self.database_key_index(key);
memo.mark_as_verified(zalsa, database_key_index);
#[cfg(feature = "accumulator")]
memo.revisions
.accumulated_inputs
.store(InputAccumulatedValues::Empty);
}
}