[GitHub] [druid] yuanlihan commented on a change in pull request #11987: Add two new array functions to Druid

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

yuanlihan commented on a change in pull request #11987:
URL: https://github.com/apache/druid/pull/11987#discussion_r760735640



##########
File path: core/src/main/java/org/apache/druid/math/expr/Function.java
##########
@@ -3422,6 +3422,100 @@ ExprEval doApply(ExprEval lhsExpr, ExprEval rhsExpr)
     }
   }
 
+  class ArrayContainsContiguousSubarrayFunction extends ArraysFunction
+  {
+    @Override
+    public String name()
+    {
+      return "array_contains_contiguous_subarray";
+    }
+
+    @Override
+    public boolean hasArrayOutput()
+    {
+      return true;
+    }
+
+    @Nullable
+    @Override
+    public ExpressionType getOutputType(Expr.InputBindingInspector inputTypes, List<Expr> args)
+    {
+      return ExpressionType.LONG;
+    }
+
+    @Override
+    ExprEval doApply(ExprEval lhsExpr, ExprEval rhsExpr)

Review comment:
       Hi @LakshSingla, thanks for the comment.
   > The implementation seems to have complexity of O(length1 * (length1-length2)), which seems suboptimal if we used something like KMP. Maybe something like Collections#indexOfSublist can be better, but it seems that it might be using the same algorithm underneath. In any case, I think it could be optimized further, and we might not wanna go with the naive implementation if the operands we expect have can have a decent length. String searching
   
   I got your point that you're concerned about the performance of the array function here. Actually, during SQL function translation, it'll try to void necessary array comparing by leveraging a serial of dimension filters which can use Druid's bitmap index to speed up filtering. 
   
   




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