fix: escape embedded backticks in column names (#316)

ClickHouse.Driver.Tests/BulkCopy/BulkCopyTests.cs

@@ -322,16 +322,30 @@ public async Task ShouldExecuteInsertWithBacktickedColumns()
     {
         var targetTable = CreateTableName();
 
-        await connection.ExecuteStatementAsync($"CREATE TABLE {targetTable} (`field.id` Nullable(UInt8), `@value` Nullable(UInt8)) ENGINE Memory");
+        await connection.ExecuteStatementAsync(
+            $"CREATE TABLE {targetTable} (`field.id` Nullable(UInt8), `@value` Nullable(UInt8)) ENGINE Memory");
 
         using var bulkCopy = new ClickHouseBulkCopy(connection)
         {
             DestinationTableName = targetTable,
-            ColumnNames = new[] { "`field.id`, `@value`" }
+            ColumnNames = new[] { "field.id", "@value" }
         };
-        await bulkCopy.WriteToServerAsync(Enumerable.Repeat(new object[] { 5, 5 }, 5));
 
-        using var reader = await connection.ExecuteReaderAsync($"SELECT * FROM {targetTable}");
+        await bulkCopy.WriteToServerAsync(
+            Enumerable.Repeat(new object[] { 5, 5 }, 5));
+
+        using var reader = await connection.ExecuteReaderAsync(
+            $"SELECT `field.id`, `@value` FROM {targetTable}");
+
+        var rows = 0;
+        while (await reader.ReadAsync())
+        {
+            Assert.That(reader.GetValue(0), Is.EqualTo((byte)5));
+            Assert.That(reader.GetValue(1), Is.EqualTo((byte)5));
+            rows++;
+        }
+
+        Assert.That(rows, Is.EqualTo(5));
     }
 
     [Test]

ClickHouse.Driver.Tests/Utility/QuotedStringTests.cs

@@ -0,0 +1,71 @@
+using ClickHouse.Driver.Utility;
+
+namespace ClickHouse.Driver.Tests.Utility;
+
+[TestFixture]
+public class QuotedStringTests
+{
+    [Test]
+    public void EncloseColumnName_EscapesInteriorBackticks()
+    {
+        var result = "weird`name".EncloseColumnName();
+
+        Assert.That(result, Is.EqualTo("`weird\\`name`"));
+    }
+
+    [Test]
+    public void EncloseColumnName_AlreadyEnclosedButNeedsEscape_EscapesInterior()
+    {
+        var result = "`col`name`".EncloseColumnName();
+
+        Assert.That(result, Is.EqualTo("`\\`col\\`name\\``"));
+    }
+
+    [Test]
+    public void EncloseColumnName_HandlesNullOrEmpty()
+    {
+        Assert.That(StringExtensions.EncloseColumnName(null), Is.Null);
+        Assert.That(StringExtensions.EncloseColumnName(string.Empty), Is.EqualTo(string.Empty));
+    }
+
+    [Test]
+    public void QuoteSingle_AddsOuterSingleQuotes()
+    {
+        var input = "O\\'Reilly";
+        var result = input.QuoteSingle();
+
+        Assert.That(result, Is.EqualTo("'O\\'Reilly'"));
+    }
+
+    [Test]
+    public void QuoteSingle_EmptyString_ReturnsQuotedEmptyString()
+    {
+        Assert.That(string.Empty.QuoteSingle(), Is.EqualTo("''"));
+    }
+
+    [Test]
+    public void QuoteDouble_AddsOuterDoubleQuotes()
+    {
+        var input = "Product \\\"Items\\\"";
+        var result = input.QuoteDouble();
+
+        Assert.That(result, Is.EqualTo("\"Product \\\"Items\\\"\""));
+    }
+
+    [Test]
+    public void QuoteDouble_EmptyString_ReturnsQuotedEmptyString()
+    {
+        Assert.That(string.Empty.QuoteDouble(), Is.EqualTo("\"\""));
+    }
+
+    [TestCase("O\\'Reilly", "'O\\'Reilly'")]
+    [TestCase("Product \\\"Items\\\"", "\"Product \\\"Items\\\"\"")]
+    public void Quote_AddsOuterQuotes(string input, string expected)
+    {
+        var result = input.Contains('\'')
+            ? input.QuoteSingle()
+            : input.QuoteDouble();
+
+        Assert.That(result, Is.EqualTo(expected));
+    }
+}

ClickHouse.Driver/Utility/StringExtensions.cs

@@ -9,10 +9,10 @@ internal static class StringExtensions
     public static string Escape(this string str) => str.Replace("\\", "\\\\").Replace("\'", "\\\'").Replace("\n", "\\n").Replace("\t", "\\t");
 
     [SuppressMessage("Performance", "CA1865:Use char overload", Justification = "Not available in net462")]
-    public static string QuoteSingle(this string str) => str.StartsWith("'", StringComparison.InvariantCulture) && str.EndsWith("'", StringComparison.InvariantCulture) ? str : $"'{str}'";
+    public static string QuoteSingle(this string str) => $"'{str}'";
 
     [SuppressMessage("Performance", "CA1865:Use char overload", Justification = "Not available in net462")]
-    public static string QuoteDouble(this string str) => str.StartsWith("\"", StringComparison.InvariantCulture) && str.EndsWith("\"", StringComparison.InvariantCulture) ? str : $"\"{str}\"";
+    public static string QuoteDouble(this string str) => $"\"{str}\"";
 
     /// <summary>
     /// Appends a value prefixed with its length, so that a concatenation of appended values maps back to
@@ -26,16 +26,14 @@ public static StringBuilder AppendLengthPrefixed(this StringBuilder builder, str
 
     /// <summary>
     /// Encloses column name in backticks (`). Escapes ` symbol if met inside name
-    /// Does nothing if column is already enclosed
+    /// The input is always treated as an unquoted column name.
     /// </summary>
     /// <param name="str">Column name</param>
     /// <returns>Backticked column name</returns>
     public static string EncloseColumnName(this string str)
     {
         if (string.IsNullOrEmpty(str))
             return str;
-        if (str[0] == '`' && str[str.Length - 1] == '`')
-            return str; // Early return if already enclosed
 
         var builder = new StringBuilder();
         builder.Append('`');

changelog.d/316-quoted-identifiers.fixes.md

@@ -0,0 +1 @@
+* Fixed `EncloseColumnName` returning already-delimited input without escaping embedded backticks ([#316](https://github.com/ClickHouse/clickhouse-cs/issues/316)).