feat(etl): implement ColumnRenameTransformer

Add transformer for renaming columns in the data stream during ETL. Supports case-insensitive column name matching and multiple renames.
2026-01-03 09:13:02 -05:00
parent f1b7809a45
commit 81cb0df6bf
2 changed files with 120 additions and 0 deletions
@@ -0,0 +1,51 @@
+using System.Data;
+
+namespace JdeScoping.DataSync.Etl.Transformers;
+
+/// <summary>
+/// A data transformer that renames specified columns in the data stream.
+/// Columns are matched by name (case-insensitive).
+/// </summary>
+public class ColumnRenameTransformer : DataTransformerBase
+{
+    private readonly Dictionary<string, string> _renames;
+    private string[]? _outputNames;
+    private Dictionary<string, int>? _nameToOrdinal;
+
+    /// <inheritdoc />
+    public override string TransformerName => $"RenameColumns:{_renames.Count}";
+
+    /// <summary>
+    /// Creates a new ColumnRenameTransformer that renames the specified columns.
+    /// </summary>
+    /// <param name="renames">Tuples of (OldName, NewName) for columns to rename (case-insensitive matching).</param>
+    public ColumnRenameTransformer(params (string OldName, string NewName)[] renames)
+    {
+        ArgumentNullException.ThrowIfNull(renames);
+        _renames = renames.ToDictionary(r => r.OldName, r => r.NewName, StringComparer.OrdinalIgnoreCase);
+    }
+
+    /// <inheritdoc />
+    protected override void OnInitialize(IDataReader source)
+    {
+        _outputNames = new string[source.FieldCount];
+        _nameToOrdinal = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+        for (int i = 0; i < source.FieldCount; i++)
+        {
+            var originalName = source.GetName(i);
+            var outputName = _renames.TryGetValue(originalName, out var newName) ? newName : originalName;
+            _outputNames[i] = outputName;
+            _nameToOrdinal[outputName] = i;
+        }
+    }
+
+    /// <inheritdoc />
+    public override string GetName(int ordinal, IDataReader source) => _outputNames![ordinal];
+
+    /// <inheritdoc />
+    public override int GetOrdinal(string name, IDataReader source)
+    {
+        if (_nameToOrdinal!.TryGetValue(name, out var ordinal)) return ordinal;
+        throw new IndexOutOfRangeException($"Column '{name}' not found.");
+    }
+}