clintropolis commented on code in PR #14287:
URL: https://github.com/apache/druid/pull/14287#discussion_r1198202220
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processing/src/main/java/org/apache/druid/math/expr/Expr.java:
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@@ -185,10 +185,28 @@ default <T> ExprVectorProcessor<T>
asVectorProcessor(VectorInputBindingInspector
throw Exprs.cannotVectorize(this);
}
+
+ /**
+ * Decorates the cache key builder by adding extra elements if stringify
alone is not sufficient
+ * to create the cache key. Override this method in such cases then, for
e.g. {@link org.apache.druid.query.expression.LookupExprMacro}}
+ * @param builder
+ */
Review Comment:
nit: i dont think we really need to link to things that override this,
rather we should indicate that it is for use to append additional information
to the default implementation of `getCacheKey`, such as if the expression
relies on some external state. How about something like:
```suggestion
/**
* Decorates the {@link CacheKeyBuilder} for the default implementation of
{@link #getCacheKey()}. The default cache
* key implementation includes the output of {@link #stringify()} and then
uses a {@link Shuttle} to call this method
* on all children. The stringified representation is sufficient for most
expressions, but for any which rely on
* external state that might change, this method allows the cache key to
change when the state does, even if the
* expression itself is otherwise the same.
*/
```
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