aho135 commented on code in PR #19386:
URL: https://github.com/apache/druid/pull/19386#discussion_r3229647389
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processing/src/test/java/org/apache/druid/math/expr/ExprTest.java:
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@@ -221,6 +221,27 @@ public void testEqualsContractForNullDoubleExpr()
.verify();
}
+ /**
+ * now() depends on wall-clock time, so its cache key must not be stable
across calls — otherwise queries containing
+ * now() can hit a stale cached result. NowExpression overrides {@link
Expr#decorateCacheKeyBuilder} to mix in
+ * nanoTime, which makes any containing Expr produce a fresh key on every
{@link Expr#getCacheKey()} call.
+ */
+ @Test
+ public void testNowExprCacheKeyIsNotStable()
+ {
+ Expr now = Parser.parse("now()", ExprMacroTable.nil());
+ byte[] k1 = now.getCacheKey();
+ byte[] k2 = now.getCacheKey();
+ Assertions.assertFalse(java.util.Arrays.equals(k1, k2), "bare now() cache
key must change across calls");
+
+ // Verify the same instability propagates when now() is nested in a parent
expression.
+ Expr nested = Parser.parse("now() > 0", ExprMacroTable.nil());
+ Assertions.assertFalse(
+ java.util.Arrays.equals(nested.getCacheKey(), nested.getCacheKey()),
Review Comment:
```suggestion
Arrays.equals(nested.getCacheKey(), nested.getCacheKey()),
```
Can be imported
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