[GitHub] [druid] rash67 commented on a diff in pull request #13086: Optimize CompressedBigDecimal compareTo()

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

rash67 commented on code in PR #13086:
URL: https://github.com/apache/druid/pull/13086#discussion_r970271401


##########
extensions-contrib/compressed-bigdecimal/src/main/java/org/apache/druid/compressedbigdecimal/CompressedBigDecimal.java:
##########
@@ -276,13 +278,48 @@ protected static <S> int signumInternal(int size, S rhs, ToIntBiFunction<S, Inte
    */
   @Override
   public int compareTo(CompressedBigDecimal o)
+  {
+    return compareTo(o, false);
+  }
+
+  public int compareTo(CompressedBigDecimal o, boolean expectOptimized)
   {
     if (super.equals(o)) {
       return 0;
+    } else if (getScale() == o.getScale() && getArraySize() == o.getArraySize()) {
+      return compareCompressedBigDecimal(this, o, getArraySize());
+    } else {
+      if (expectOptimized) {
+        throw new RE("expected optimized path");
+      }
+
+      return this.toBigDecimal().compareTo(o.toBigDecimal());
+    }
+  }
+
+  public static int compareCompressedBigDecimal(CompressedBigDecimal lhs, CompressedBigDecimal rhs, int length)
+  {
+    int[] result = new int[length];
+    int borrow = 0;
+
+    for (int i = 0; i < length; i++) {
+      long x = (INT_MASK & lhs.getArrayEntry(i)) - (INT_MASK & rhs.getArrayEntry(i)) - borrow;
+      borrow = 0;
+
+      if (x < 0) {
+        borrow = 1;
+        x += 1L << 32;
+      }
+
+      result[i] = (int) x;
     }
-    return this.toBigDecimal().compareTo(o.toBigDecimal());
+
+    int signum = signumInternal(result.length, result, (r, i) -> r[i]);

Review Comment:
   not sure if i should create a concrete class or concrete impl of signumInternal for this case to avoid megamorphic callsite for the lambda passed in?



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