jon-wei commented on a change in pull request #7588: multi-value string column
support for expressions
URL: https://github.com/apache/incubator-druid/pull/7588#discussion_r290957055
##########
File path: core/src/main/java/org/apache/druid/math/expr/Expr.java
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@@ -56,23 +70,180 @@ default Object getLiteralValue()
throw new ISE("Not a literal");
}
+ /**
+ * Returns the string identifier of an {@link IdentifierExpr}, else null
+ */
+ @Nullable
+ default String getIdentifierIfIdentifier()
+ {
+ // overridden by things that are identifiers
+ return null;
+ }
+
+ /**
+ * Evaluate the {@link Expr} with the bindings which supply {@link
IdentifierExpr} with their values, producing an
+ * {@link ExprEval} with the result.
+ */
@Nonnull
ExprEval eval(ObjectBinding bindings);
+ /**
+ * Programmatically inspect the {@link Expr} tree with a {@link Visitor}.
Each {@link Expr} is responsible for
+ * ensuring the {@link Visitor} can visit all of it's {@link Expr} children
before visiting itself.
+ */
+ void visit(Visitor visitor);
+
+ /**
+ * Programatically rewrite the {@link Expr} tree with a {@link Shuttle}.Each
{@link Expr} is responsible for
+ * ensuring the {@link Shuttle} can visit all of it's {@link Expr} children,
as well as updating it's children
+ * {@link Expr} with the results from the {@link Shuttle}, before finally
visiting an updated form of itself.
+ */
+ Expr visit(Shuttle shuttle);
+
+ /**
+ * Examing the usage of {@link IdentifierExpr} children of an {@link Expr},
constructing a {@link BindingDetails}
Review comment:
Examing -> Examine
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