What causes "Expected key [%s] to be a Long, but got [%s]" in apache/druid?

Correct the context JSON so the key holds a JSON number or numeric string.

apache/druid · error · BadQueryContextException

Expected key [%s] to be a Long, but got [%s]

Error message

Expected key [%s] to be a Long, but got [%s]

What it means

QueryContexts.getAsLong(key, value) throws badTypeException with this message when the context value's class cannot be interpreted as a Long at all — it is neither null, a Number, nor a String (e.g. Boolean, Map, List). The exception includes the key and the value's actual type.

Source

Thrown at processing/src/main/java/org/apache/druid/query/QueryContexts.java:424

      return ((Number) value).longValue();
    } else if (value instanceof String) {
      try {
        return Numbers.parseLong(value);
      }
      catch (NumberFormatException ignored) {

        // Attempt to handle trivial decimal values: 12.00, etc.
        // This mimics how Jackson will convert "12.00" to a Long on request.
        try {
          return new BigDecimal((String) value).longValueExact();
        }
        catch (Exception nfe) {
          // That didn't work either. Give up.
          throw badValueException(key, "in long format", value);
        }
      }
    }
    throw badTypeException(key, "a Long", value);
  }

  /**
   * Get the value of a context value as an {@code long}. The value is expected
   * to be {@code null}, a string or a {@code Number} object.
   */
  public static long getAsLong(
      final String key,
      final Object value,
      final long defaultValue
  )
  {
    Long val = getAsLong(key, value);
    return val == null ? defaultValue : val;
  }

  /**
   * Get the value of a context value as an {@code Float}. The value is expected

View on GitHub (pinned to 9b90983fd2)

Solutions

Correct the context JSON so the key holds a JSON number or numeric string.
In code, put a Long/Integer: context.put(key, 123456789L).
Check for key-name typos that cause a value of the wrong shape to land under this key.
Catch the exception and fall back to the default value.

Example fix

// before
{"timeout": false}   // boolean under numeric key -> IAE
// after
{"timeout": 30000}

Defensive patterns

Strategy: type-guard

Validate before calling

Object v = context.get(key);
if (v != null && !(v instanceof Number) && !(v instanceof String)) {
  throw new IllegalArgumentException("Context key '" + key + "' must be numeric, got: " + v.getClass().getSimpleName());
}

Type guard

boolean isContextNumber(Object v) { return v == null || v instanceof Number || v instanceof String; }

Try / catch

try {
  return query.getContextValue(key, defaultLong);
} catch (IllegalArgumentException e) {
  LOG.warn(e, "Wrong type for context key [%s], using default", key);
  return defaultLong;
}

Prevention

Keep boolean flags and numeric limits under distinct, correctly named context keys.
Validate deserialized context maps before handing them to query execution.
Use typed context builders rather than raw Map<String, Object> puts.

When it happens

Trigger: Calling QueryContexts.getAsLong(key, value) or query.getContextValue(key, long default) when the context map stores a Boolean, JSON object/array, or other non-numeric non-string object under a long-typed context key.

Common situations: A boolean or nested-config value placed under a numeric key by mistake; clients sending JSON objects where a number is expected; earlier code paths that stored raw deserialized JSON trees into the context.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/cfbce57e8dea0bee. Report an issue: GitHub.