private Expression partitionFilter(Integer specId) {
    if (partitionFilters == null || partitionFilters.isEmpty()) {
      return Expressions.alwaysTrue();
    }

    Expression filter = partitionFilters.get(specId);
    return filter == null ? Expressions.alwaysFalse() : filter;
  }
Base results on files in the snapshot that was current as of a timestamp.

@param timestampMillis a timestamp in milliseconds
@return this for method chaining
amoro-format-iceberg/src/main/java/org/apache/iceberg/IcebergFindFiles.java