innerJoin static method

Datacat innerJoin(Datacat left, Datacat right, String on)

Performs an inner join on two Datacat objects based on the column on.

Implementation

static Datacat innerJoin(Datacat left, Datacat right, String on) {
  int leftIndex = left.columns.indexOf(on);
  int rightIndex = right.columns.indexOf(on);
  if (leftIndex == -1 || rightIndex == -1) {
    throw ArgumentError('Join column "$on" must exist in both data objects.');
  }
  List<String> newColumns = List.from(left.columns);
  for (final col in right.columns) {
    if (col != on && !newColumns.contains(col)) {
      newColumns.add(col);
    }
  }
  List<List<dynamic>> newRows = [];
  final Map<dynamic, List<List<dynamic>>> rightIndexMap = {};
  for (final row in right.rows) {
    var key = row[rightIndex];
    rightIndexMap.putIfAbsent(key, () => []).add(row);
  }
  for (final lRow in left.rows) {
    var key = lRow[leftIndex];
    final matchingRows = rightIndexMap[key];
    if (matchingRows != null) {
      for (final rRow in matchingRows) {
        List<dynamic> combinedRow = [];
        combinedRow.addAll(lRow);
        for (int i = 0; i < right.columns.length; i++) {
          if (i == rightIndex) continue;
          combinedRow.add(rRow[i]);
        }
        newRows.add(combinedRow);
      }
    }
  }
  return Datacat(columns: newColumns, rows: newRows);
}