apache/druid · error · IllegalArgumentException

Column[%d] is not a valid column for segment[%s]

Error message

Column[%d] is not a valid column for segment[%s]

What it means

BroadcastSegmentIndexedTable.columnReader(int) validates the requested column index against the table's rowSignature. If the index is out of bounds (>= signature size or negative), Druid throws this IllegalArgumentException naming the segment, protecting downstream readers from selecting a nonexistent column.

Source

Thrown at processing/src/main/java/org/apache/druid/segment/join/table/BroadcastSegmentIndexedTable.java:194

  }

  @Override
  public int numRows()
  {
    return queryableIndex.getNumRows();
  }

  @Override
  public Index columnIndex(int column)
  {
    return RowBasedIndexedTable.getKeyColumnIndex(column, keyColumnsIndexes);
  }

  @Override
  public Reader columnReader(int column)
  {
    if (!rowSignature.contains(column)) {
      throw new IAE("Column[%d] is not a valid column for segment[%s]", column, segment.getId());
    }
    final SimpleAscendingOffset offset = new SimpleAscendingOffset(queryableIndex.getNumRows());
    final BaseColumn baseColumn = queryableIndex.getColumnHolder(rowSignature.getColumnName(column)).getColumn();
    final BaseObjectColumnValueSelector<?> selector = baseColumn.makeColumnValueSelector(offset);

    return new Reader()
    {
      @Nullable
      @Override
      public Object read(int row)
      {
        offset.setCurrentOffset(row);
        return selector.getObject();
      }

      @Override
      public void close() throws IOException
      {

View on GitHub (pinned to 9b90983fd2)

Solutions

1. Verify the column index against rowSignature.size() before calling columnReader
2. Drop/rebuild the broadcast table or refresh cached joinables after schema changes so indexes match the current signature
3. Ensure join clause column ordering matches the broadcast segment's rowSignature

Example fix

// before
reader = table.columnReader(3); // signature has 2 columns
// after
if (column < table.rowSignature().size()) { reader = table.columnReader(column); }

if (column < 0 || column >= table.rowSignature().size())
  throw new IllegalArgumentException("column " + column + " out of range for broadcast table");
Reader r = table.columnReader(column);

try { r = table.columnReader(col); } catch (IAE e) { log.error("stale join table signature for segment {}", e.getMessage()); refreshTable(); }

When it happens

Trigger: Calling columnReader with an int column index not present in the table's RowSignature, usually from a join key/column mapping computed against a different signature version than the loaded segment.

Common situations: Segment replaced/updated so its signature no longer matches the query's expected column order; join cache keys built before a broker/server restart with a changed table schema; bugs in key column index computation for broadcast tables.

Related errors

• Column[%d] is not a valid column for the frame based datasou
• BroadcastTablesTooLarge
• Column[%s] does not start with prefix[%s]
• Detected duplicate prefix in join clauses: [%s]
• Detected conflicting prefixes in join clauses: [%s, %s]

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/65f85e785311c4bd. Report an issue: GitHub.