redis/jedis · error · IllegalStateException

REDUCE COLLECT cannot mix FIELDS * with explicit field names

Error message

REDUCE COLLECT cannot mix FIELDS * with explicit field names

What it means

CollectReducer's REDUCE COLLECT lets you collect either an explicit list of fields or all fields (FIELDS *), but not both. Calling fields(String...) after fieldsAll() was already set throws this IllegalStateException because the two configurations are mutually exclusive in the generated aggregate query.

Solutions

1. Choose one mode: call fields(...) with explicit names OR fieldsAll(), never both on the same reducer
2. If a default of all-fields exists, clear/reset the reducer (build a new CollectReducer) before adding explicit fields
3. Refactor dynamic builders so the mode decision happens once before adding field names

Example fix

// before
CollectReducer r = new CollectReducer().fieldsAll().fields("@title"); // IllegalStateException
// after
CollectReducer r = new CollectReducer().fields("@title", "@body");
// or
CollectReducer r = new CollectReducer().fieldsAll();

if (useAllFields && explicitFields.length > 0) {
  throw new IllegalStateException("Choose either fieldsAll() or fields(...), not both");
}

null

try {
  reducer.fields("@title");
} catch (IllegalStateException e) {
  // fieldsAll() already set — rebuild the reducer in a single mode
}

When it happens

Trigger: Calling reducer.fieldsAll() followed by reducer.fields("@a","@b") on the same CollectReducer instance (builder-chain or fluent reuse).

Common situations: Building reducers dynamically and appending field names after defaulting to all-fields; copy-pasting reducer configuration where fieldsAll() appears earlier in the chain; reusing a shared reducer builder for multiple queries.

Related errors

• REDUCE COLLECT requires either fields(...) or fieldsAll()…
• DIALECT=0 cannot be set.
• No connections available from connection provider
• No more aggregation results available
• Failed to fetch next aggregation batch

AI-assisted analysis of redis/jedis@6dac31d4c2 (2026-09-08). Data as JSON: /api/errors/9c90897f562b2cd2. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/redis/clients/jedis/search/aggr/CollectReducer.java:76

  private boolean allFields = false;
  private final List<String> fields = new ArrayList<>();
  private final List<SortedField> sortFields = new ArrayList<>();
  private Integer limitOffset;
  private Integer limitCount;

  CollectReducer() {
    super("COLLECT");
  }

  /**
   * Project the named fields for every document in the group. Use {@code @__key}, {@code @__score}
   * or document field names (e.g. {@code @title}).
   * <p>
   * Mutually exclusive with {@link #fieldsAll()}.
   */
  public CollectReducer fields(String... fields) {
    if (this.allFields) {
      throw new IllegalStateException(
          "REDUCE COLLECT cannot mix FIELDS * with explicit field names");
    }
    Collections.addAll(this.fields, fields);
    return this;
  }

  /**
   * Project every field available in the current input row ({@code FIELDS *}).
   * <p>
   * Per the COLLECT specification, {@code *} does not trigger an implicit load — fields must
   * already be in the pipeline (typically via {@code LOAD *} or because they are grouping keys /
   * reducer aliases).
   * <p>
   * Mutually exclusive with {@link #fields(String...)}.
   */
  public CollectReducer fieldsAll() {
    if (!this.fields.isEmpty()) {
      throw new IllegalStateException(

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