clintropolis commented on a change in pull request #10370:
URL: https://github.com/apache/druid/pull/10370#discussion_r486756143
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File path: core/src/main/java/org/apache/druid/math/expr/Expr.java
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@@ -116,16 +116,39 @@ default String getBindingIfIdentifier()
void visit(Visitor visitor);
/**
- * Programatically rewrite the {@link Expr} tree with a {@link Shuttle}.Each
{@link Expr} is responsible for
+ * Programatically rewrite the {@link Expr} tree with a {@link Shuttle}.
Each {@link Expr} is responsible for
* ensuring the {@link Shuttle} can visit all of its {@link Expr} children,
as well as updating its children
* {@link Expr} with the results from the {@link Shuttle}, before finally
visiting an updated form of itself.
*/
Expr visit(Shuttle shuttle);
/**
- * Examine the usage of {@link IdentifierExpr} children of an {@link Expr},
constructing a {@link BindingDetails}
+ * Examine the usage of {@link IdentifierExpr} children of an {@link Expr},
constructing a {@link BindingAnalysis}
*/
- BindingDetails analyzeInputs();
+ BindingAnalysis analyzeInputs();
+
+ /**
+ * Given an {@link InputBindingTypes}, compute what the output {@link
ExprType} will be for this expression. A return
+ * value of null indicates that the given type information was not enough to
resolve the output type, so the
+ * expression must be evaluated using default {@link #eval} handling where
types are only known after evaluation,
+ * through {@link ExprEval#type}.
+ */
+ @Nullable
+ default ExprType getOutputType(InputBindingTypes inputTypes)
+ {
+ return null;
+ }
+
+ /**
+ * Mechanism to supply input types for the bindings which will back {@link
IdentifierExpr}, to use in the aid of
+ * inferring the output type of an expression with {@link #getOutputType}. A
null value means that either the binding
Review comment:
not long term probably, but currently this will be backed by
`ColumnCapabilities` from a `ColumnInspector`, which does not currently
distinguish between those 2 things for all implementations.
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