apache/druid · error · IAE

An inline table requires one or more rows of data in the '%s

Error message

An inline table requires one or more rows of data in the '%s' property

What it means

When converting user args to an inline input source JSON map, InlineInputSourceDefn.convertArgsToSourceMap requires at least one row of data in the 'data' property. The underlying Druid InlineInputSource does not support zero rows, so an empty data list is rejected. Thrown as IllegalArgumentException.

Source

Thrown at server/src/main/java/org/apache/druid/catalog/model/table/InlineInputSourceDefn.java:98

      throw new IAE("An inline input source must provide a format.");
    }
    if (CollectionUtils.isNullOrEmpty(table.resolvedTable().spec().columns())) {
      throw new IAE("An inline input source must provide one or more columns");
    }

    super.validate(table);
  }

  @Override
  protected void convertArgsToSourceMap(Map<String, Object> jsonMap, Map<String, Object> args)
  {
    jsonMap.put(InputSource.TYPE_PROPERTY, InlineInputSource.TYPE_KEY);
    List<String> data = CatalogUtils.getStringArray(args, DATA_PROPERTY);

    // Would be nice, from a completeness perspective, for the inline data
    // source to allow zero rows of data. However, such is not the case.
    if (CollectionUtils.isNullOrEmpty(data)) {
      throw new IAE(
          "An inline table requires one or more rows of data in the '%s' property",
          DATA_PROPERTY
      );
    }
    jsonMap.put(DATA_FIELD, String.join("\n", data));
  }

  @Override
  protected ExternalTableSpec convertCompletedTable(
      final ResolvedExternalTable table,
      final Map<String, Object> args,
      final List<ColumnSpec> columns
  )
  {
    if (!args.isEmpty()) {
      throw new ISE("Cannot provide arguments for an inline table");
    }
    if (!CollectionUtils.isNullOrEmpty(columns)) {

View on GitHub (pinned to 9b90983fd2)

Solutions

Provide one or more rows in the 'data' property (each list element becomes a line)
If no data exists yet, use a different input source type or defer table creation
Check the code path generating the data list for empty-result handling

Example fix

// before
args: {"data":[]}
// after
args: {"data":["1,foo","2,bar"]}

Defensive patterns

Strategy: validation

Validate before calling

List<String> data = (List<String>) args.get("data");
if (data == null || data.isEmpty()) {
  throw new IllegalArgumentException("inline table requires non-empty 'data' property");
}

Try / catch

try { defn.convertArgsToSourceMap(args); } catch (IAE e) { if (e.getMessage().contains("one or more rows of data")) { /* supply data rows */ } else { throw e; } }

Prevention

Check upstream data population steps for empty results before creating the table
Do not create inline tables as placeholders with no rows
Default-template inline tables should include sample data

When it happens

Trigger: Calling convertArgsToSourceMap with args whose DATA_PROPERTY ('data') string array is missing, null, or empty.

Common situations: Template renders with no data rows; user saves an inline table intending to add data later; an upstream step that was supposed to populate data produced an empty list.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/46d73fc1b7544217. Report an issue: GitHub.