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a2198f1f8a
If a query observes an untracked read, it gets changed_at equal to the current revision. When we re-validate the query later, if it doesn't do an untracked read this time, it gets changed_at equal to the maximum of the dependencies. Crucially, this new changed_at may be **older** then the previous value of changed_at. That is, we break the rule that `changed_at` monotonically increases. This can lead to missed re-executions down the line (see the added test). closes #66
85 lines
2.4 KiB
Rust
85 lines
2.4 KiB
Rust
use crate::implementation::{TestContext, TestContextImpl};
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use salsa::Database;
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salsa::query_group! {
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pub(crate) trait MemoizedVolatileContext: TestContext {
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// Queries for testing a "volatile" value wrapped by
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// memoization.
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fn memoized2() -> usize {
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type Memoized2;
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}
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fn memoized1() -> usize {
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type Memoized1;
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}
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fn volatile() -> usize {
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type Volatile;
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storage volatile;
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}
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}
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}
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fn memoized2(db: &impl MemoizedVolatileContext) -> usize {
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db.log().add("Memoized2 invoked");
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db.memoized1()
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}
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fn memoized1(db: &impl MemoizedVolatileContext) -> usize {
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db.log().add("Memoized1 invoked");
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let v = db.volatile();
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v / 2
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}
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fn volatile(db: &impl MemoizedVolatileContext) -> usize {
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db.log().add("Volatile invoked");
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db.clock().increment()
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}
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#[test]
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fn volatile_x2() {
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let query = TestContextImpl::default();
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// Invoking volatile twice doesn't execute twice, because volatile
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// queries are memoized by default.
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query.volatile();
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query.volatile();
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query.assert_log(&["Volatile invoked"]);
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}
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/// Test that:
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///
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/// - On the first run of R0, we recompute everything.
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/// - On the second run of R1, we recompute nothing.
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/// - On the first run of R1, we recompute Memoized1 but not Memoized2 (since Memoized1 result
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/// did not change).
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/// - On the second run of R1, we recompute nothing.
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/// - On the first run of R2, we recompute everything (since Memoized1 result *did* change).
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#[test]
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fn revalidate() {
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let query = TestContextImpl::default();
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query.memoized2();
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query.assert_log(&["Memoized2 invoked", "Memoized1 invoked", "Volatile invoked"]);
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query.memoized2();
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query.assert_log(&[]);
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// Second generation: volatile will change (to 1) but memoized1
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// will not (still 0, as 1/2 = 0)
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query.salsa_runtime().next_revision();
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query.memoized2();
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query.assert_log(&["Memoized2 invoked", "Memoized1 invoked", "Volatile invoked"]);
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query.memoized2();
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query.assert_log(&[]);
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// Third generation: volatile will change (to 2) and memoized1
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// will too (to 1). Therefore, after validating that Memoized1
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// changed, we now invoke Memoized2.
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query.salsa_runtime().next_revision();
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query.memoized2();
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query.assert_log(&["Memoized2 invoked", "Memoized1 invoked", "Volatile invoked"]);
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query.memoized2();
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query.assert_log(&[]);
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}
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