[GitHub] [druid] clintropolis commented on a change in pull request #11104: expression aggregator

[GitBox <gi...@apache.org>]

clintropolis commented on a change in pull request #11104:
URL: https://github.com/apache/druid/pull/11104#discussion_r615177984



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File path: core/src/main/java/org/apache/druid/math/expr/Function.java
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@@ -460,6 +474,118 @@ public ExprEval apply(List<Expr> args, Expr.ObjectBinding bindings)
     abstract ExprEval doApply(ExprEval lhsExpr, ExprEval rhsExpr);
   }
 
+  /**
+   * Scaffolding for a 2 argument {@link Function} which accepts one array and one scalar input and adds the scalar
+   * input to the array in some way.
+   */
+  abstract class ArrayAddElementFunction extends ArrayScalarFunction
+  {
+    @Override
+    public boolean hasArrayOutput()
+    {
+      return true;
+    }
+
+    @Nullable
+    @Override
+    public ExprType getOutputType(Expr.InputBindingInspector inspector, List<Expr> args)
+    {
+      ExprType arrayType = getArrayArgument(args).getOutputType(inspector);
+      return Optional.ofNullable(ExprType.asArrayType(arrayType)).orElse(arrayType);
+    }
+
+    @Override
+    ExprEval doApply(ExprEval arrayExpr, ExprEval scalarExpr)
+    {
+      switch (arrayExpr.type()) {
+        case STRING:
+        case STRING_ARRAY:
+          return ExprEval.ofStringArray(add(arrayExpr.asStringArray(), scalarExpr.asString()).toArray(String[]::new));

Review comment:
       Ah this behavior of array functions making new arrays isn't really new, I just refactored some things to better re-use code. But yeah efficiency is not great. I don't really have any concrete solutions yet of how to make it better, at least for non-vectorized expressions, but I will think about it and try to leave a comment.




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