adityamukho · Oct 24, 2026 · Oct 24, 2026
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **A rule call with the float `0.0` returns the row of `-0.0` in every run** (#750), backported from v3.0.0 (#545). `0.0 == -0.0`, as patterns and predicates compare floats, but `Value`'s hash gave the two different hashes, so a join through a hash table paired them only when the process's random hash seed happened to: `[:find ?e :where (xval ?e 0.0)]` for a rule `(xval ?e ?v)` returned the entity whose value is `-0.0` in about one run in twelve and left it out otherwise, with no error. `-0.0` and `0.0` now hash alike, so the rule call returns both rows, as `[?e :m/x 0.0]` does. Every other float hashes as before. Nothing stored was wrong.
 - **An expression's `=` and `!=` equate a keyword with a ref to the entity it names** (#744), backported from v3.0.0. Patterns and joins treat the keyword `:bob` as equal to a ref to the entity `:bob` names, but `[(= ?g :bob)]` compared the two values as they are, so with `?g` bound to that ref it kept no row and `[(!= ?g :bob)]` kept the row: the same question answered differently by how the query was written, with no error. `=` and `!=` now compare as joins do, in queries, rule bodies, `not` clauses and binding expressions, against a keyword constant, a keyword value or a bound `Val(Ref)`. A keyword still equals only the same keyword, and `<`, `>`, `<=` and `>=` on a keyword or a ref are still a type mismatch (no row).
 - **`checkpoint` inside a `WriteTransaction` returns `INT-001` instead of deadlocking** (#734), backported from v3.0.0. Called on a thread that holds a `WriteTransaction`, `checkpoint` waited on the write lock that the transaction already held, so the thread hung. It now returns `INT-001`, as `execute` and `begin_write` already did, and the transaction stays usable. `prepare` and `PreparedQuery::execute` make the same check: they could not deadlock, but they ran inside the transaction while `execute` refused. Present since `WriteTransaction` was added.
 

@@ -179,7 +179,7 @@ Auto-migrates v1/v2/v3/v4/v5/v6 → v7 on open/checkpoint.
 
 ## Test Coverage
 
-**1334 tests** (1325 passing, 9 ignored; unit + integration + doc).
+**1335 tests** (1326 passing, 9 ignored; unit + integration + doc).
 See `docs/TEST_COVERAGE.md` for the full per-file breakdown.
 
 **Testing conventions** — see the Testing Conventions section below before writing any tests.

@@ -4,10 +4,10 @@
 
 | | |
 |---|---|
-| **Verified** | 2026-10-24 with `cargo test` |
-| **Passing** | 1,325 |
+| **Verified** | 2026-10-25 with `cargo test` |
+| **Passing** | 1,326 |
 | **Ignored** | 9 (see [Ignored Tests](#ignored-tests)) |
-| **Total** | 1,334, including the golden-file corpus (#391) |
+| **Total** | 1,335, including the golden-file corpus (#391) |
 
 Not counted above: the `BrowserDb` tests, which run only on wasm32 with `wasm-bindgen-test` in a browser (see [Browser](#browser)).
 
@@ -99,7 +99,8 @@ These tests compare the database against an independent answer rather than a sin
 
 - **Float constants** (`tests/float_constant_test.rs`, 2 tests; #706)
   - A float constant matches equal floats only: `1e-17` does not match `0.0`; `0.0` matches `-0.0`.
-  - Checked in a pattern, bound to a `$slot`, in a rule body, in a `not` body and in an `=` predicate; in memory, on file before and after a checkpoint, and after reopen.
+  - Checked in a pattern, bound to a `$slot`, in a rule body, as a rule call's argument, in a `not` body and in an `=` predicate; in memory, on file before and after a checkpoint, and after reopen.
+  - `Value`'s hash gives `-0.0` and `0.0` the same hash (`src/graph/types.rs` unit test, #750), so a rule call's `0.0` returns `-0.0`'s row in every run.
 - **Keyword or ref in `=` / `!=`** (`tests/keyword_ref_expression_test.rs`, 4 tests; #744)
   - An expression's `=` and `!=` equate a keyword with a ref to the entity it names, as the pattern constant and the join do: either operand order, a keyword constant or value, a bound `Val(Ref)`, a binding expression, a rule body, a `not` clause, an `or` branch and a keyword whose name is a UUID; a keyword still equals the same keyword only.
   - In memory, on file after a checkpoint, and after reopen.

@@ -92,6 +92,10 @@ impl std::hash::Hash for Value {
             Value::Float(f) => {
                 if f.is_nan() {
                     0_u8.hash(state);
+                } else if *f == 0.0 {
+                    // `-0.0 == 0.0`, so both must hash alike (#750, #545 on v3).
+                    2_u8.hash(state);
+                    0_u64.hash(state);
                 } else if f.is_sign_negative() {
                     1_u8.hash(state);
                     (-f).to_bits().hash(state);
@@ -724,4 +728,21 @@ mod tests {
             }
         }
     }
+
+    /// Equal values hash alike (#750): `-0.0 == 0.0`.
+    #[test]
+    fn equal_floats_hash_alike() {
+        use std::hash::{BuildHasher, RandomState};
+        let h = RandomState::new();
+        assert_eq!(
+            h.hash_one(Value::Float(-0.0)),
+            h.hash_one(Value::Float(0.0)),
+            "-0.0 and 0.0"
+        );
+        assert_ne!(
+            h.hash_one(Value::Float(-1.0)),
+            h.hash_one(Value::Float(1.0)),
+            "-1.0 and 1.0"
+        );
+    }
 }
@@ -50,13 +50,11 @@ fn assert_float_constants_exact(db: &Minigraf) {
         "[:find ?e :where [?e :m/x -0.0]]",
         "[:find ?e :where [?e :m/x ?v] [(= ?v 0.0)]]",
         "[:find ?e :where (zeroish ?e)]",
+        // Joined by `Value`'s hash, which once told `-0.0` from `0.0` (#750).
+        "[:find ?e :where (xval ?e 0.0)]",
     ] {
         assert_eq!(names_of(&query(db, q)), [":neg", ":zero"], "{q}");
     }
-    // A rule call's literal joins by `Value`'s hash on v2.x, which tells
-    // `-0.0` from `0.0` (v3.0.0 pairs them, #545); only `1e-17` is checked.
-    let r = query(db, "[:find ?e :where (xval ?e 0.0)]");
-    assert_eq!(names_of(&r), [":zero"], "a rule call's float argument");
     let r = query(db, "[:find ?e :where (xval ?e 0.00000000000000001)]");
     assert_eq!(names_of(&r), [":tiny"], "a rule call's float argument");
     for q in [