apache/druid · error · IllegalArgumentException

!= 0

Error message

%d != 0

What it means

Bounds-check guard in SingleIndexedInt.get: this IndexedInts always has exactly one element (size() == 1), so only index 0 is valid; any other index is a caller bug. The message '%d != 0' reports the offending index. It fires when a generic consumer (e.g. query result iteration code) reads SingleIndexedInt with an index other than 0, typically from a bad cursor/offset computation rather than bad data; only position 0 may be read.

Solutions

1. Only call get(0) on SingleIndexedInt, honoring its size()==1
2. Check `indexed.size()` and iterate only within it instead of assuming a fixed loop count
3. If you need many values, use the appropriate IndexedInts implementation rather than a single-value wrapper

Example fix

// before
for (int i = 0; i < numValues; i++) v = singleIndexedInt.get(i);
// after
for (int i = 0; i < singleIndexedInt.size(); i++) v = singleIndexedInt.get(i);

assert indexed.size() == 1; int v = indexed.get(0);

boolean isSingle(Indexed<?> col) { return col != null && col.size() == 1; }

When it happens

Trigger: Calling get(i) with a nonzero i, usually by generic code iterating a column assuming multiple values, or applying an offset to the index.

Common situations: Treating a single-valued (SingleIndexedInt-backed) column like a multi-valued one; row-holder code that adds an offset (offset + i) to indexes.

Related errors

• Index[ ] >= size[ ]
• Index[ ] >= size[ ] or < 0
• index[ ] >= size[ ] or < 0
• Actual Row count mismatch. Expected
• Attempt to add row to swapped-out sink for segment

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/43e9753a18341093. Report an issue: GitHub.

Appendix: source

Thrown at processing/src/main/java/org/apache/druid/segment/data/SingleIndexedInt.java:51

  {
  }

  public void setValue(int value)
  {
    this.value = value;
  }

  @Override
  public int size()
  {
    return 1;
  }

  @Override
  public int get(int i)
  {
    if (i != 0) {
      throw new IAE("%d != 0", i);
    }
    return value;
  }

  @Override
  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
  {
    // nothing to inspect
  }
}

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