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

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

LakshSingla commented on a change in pull request #11987:
URL: https://github.com/apache/druid/pull/11987#discussion_r756636906



##########
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:
       The implementation seems to have complexity of O(length1 * length2), which seems suboptimal if we used something like [KMP](https://en.wikipedia.org/wiki/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm). Maybe something like [Collections#indexOfSublist](https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html#indexOfSubList%28java.util.List,%20java.util.List%29) can be better.




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