feat(etl): add collision detection to ColumnRenameTransformer

2026-01-03 10:50:03 -05:00
parent ae84cb3d75
commit 0820a9b024
2 changed files with 53 additions and 1 deletions
@@ -30,10 +30,23 @@ public class ColumnRenameTransformer : DataTransformerBase
    {
        _outputNames = new string[source.FieldCount];
        _nameToOrdinal = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+
        for (int i = 0; i < source.FieldCount; i++)
        {
            var originalName = source.GetName(i);
-            var outputName = _renames.TryGetValue(originalName, out var newName) ? newName : originalName;
+            var outputName = _renames.TryGetValue(originalName, out var newName)
+                ? newName
+                : originalName;
+
+            if (_nameToOrdinal.TryGetValue(outputName, out var existingOrdinal))
+            {
+                var existingOriginal = source.GetName(existingOrdinal);
+                throw new InvalidOperationException(
+                    $"Column name collision: '{originalName}' → '{outputName}' conflicts with " +
+                    $"'{existingOriginal}' (already at ordinal {existingOrdinal}). " +
+                    $"Each output column name must be unique.");
+            }
+
            _outputNames[i] = outputName;
            _nameToOrdinal[outputName] = i;
        }