apache/druid · error · IllegalArgumentException

Index[%s] < 0

Error message

Index[%s] < 0

What it means

Indexed.checkIndex(int index, int size) is the shared static bounds validator for Indexed implementations: negative indexes throw IAE 'Index[i] < 0'. Like the GenericIndexed variant, it usually indicates an unhandled lookup miss (-1) or index arithmetic underflow.

Source

Thrown at processing/src/main/java/org/apache/druid/segment/data/Indexed.java:124

   */
  default boolean isSorted()
  {
    return false;
  }

  /**
   * Checks  if {@code index} is between 0 and {@code size}. Similar to Preconditions.checkElementIndex() except this
   * method throws {@link IAE} with custom error message.
   * <p>
   * Used here to get existing behavior(same error message and exception) of V1 {@link GenericIndexed}.
   *
   * @param index identifying an element of an {@link Indexed}
   * @param size size of the {@link Indexed}
   */
  static void checkIndex(int index, int size)
  {
    if (index < 0) {
      throw new IAE("Index[%s] < 0", index);
    }
    if (index >= size) {
      throw new IAE("Index[%d] >= size[%d]", index, size);
    }
  }
}

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Validate lookup results before get(): if (idx < 0) handle-not-found;
2. Bound-check externally supplied indexes against size() before access.
3. Refactor call sites to use Optional/null-returning lookup helpers instead of sentinel -1.

Example fix

// before
Object v = indexed.lookupOrdered(k);
return indexed.get(v);
// after
int idx = indexed.indexOf(k);
return idx < 0 ? null : indexed.get(idx);

if (index < 0 || index >= size) return null;

static <T> T safeGet(Indexed<T> idx, int i) { return (i >= 0 && i < idx.size()) ? idx.get(i) : null; }

try { return indexed.get(index); } catch (IAE e) { return null; }

When it happens

Trigger: Any Indexed implementation's get()/accessor delegating to Indexed.checkIndex with a negative index, commonly from indexOf()-style misses returning -1.

Common situations: Treating -1 from a failed lookup as valid, decrementing index 0 to -1, or passing external numeric input straight into get().

Related errors

• Index[%s] < 0
• Index[%d] >= size[%d]
• Column[%d] is not a valid column for segment[%s]
• Column[%d] is not a valid column for the frame based datasou
• Cannot build hash-join matcher on non-key-based condition: %

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/b4ea0c516a0699c3. Report an issue: GitHub.