Provide a way for SqlCertificateDatabase subclasses to override "LIMIT" keyword

Author: jstedfast

MimeKit/Cryptography/SQLServerCertificateDatabase.cs

@@ -243,33 +243,16 @@ protected override void RemoveIndex (DbConnection connection, string tableName,
 		}
 
 		/// <summary>
-		/// Gets the database command to select the record matching the specified certificate.
+		/// Limit the query results to a single record.
 		/// </summary>
 		/// <remarks>
-		/// Gets the database command to select the record matching the specified certificate.
+		/// Modifies the SQL <c>SELECT</c> <paramref name="query"/> to limit the query results to a single record.
 		/// </remarks>
-		/// <returns>The database command.</returns>
-		/// <param name="connection">The database connection.</param>
-		/// <param name="certificate">The certificate.</param>
-		/// <param name="fields">The fields to return.</param>
-		protected override DbCommand GetSelectCommand (DbConnection connection, X509Certificate certificate, X509CertificateRecordFields fields)
+		/// <param name="query">A <see cref="StringBuilder"/> containing an SQL <c>SELECT</c> query.</param>
+		/// <returns>A modified SQL query that will limit the results to a single record.</returns>
+		protected override StringBuilder LimitToOne (StringBuilder query)
 		{
-			var fingerprint = certificate.GetFingerprint ().ToLowerInvariant ();
-			var serialNumber = certificate.SerialNumber.ToString ();
-			var issuerName = certificate.IssuerDN.ToString ();
-			var command = CreateCommand ();
-			var query = CreateSelectQuery (fields).Replace ("SELECT", "SELECT top 1");
-
-			// FIXME: Is this really the best way to query for an exact match of a certificate?
-			query = query.Append (" WHERE ISSUERNAME = @ISSUERNAME AND SERIALNUMBER = @SERIALNUMBER AND FINGERPRINT = @FINGERPRINT");
-			command.AddParameterWithValue ("@ISSUERNAME", issuerName);
-			command.AddParameterWithValue ("@SERIALNUMBER", serialNumber);
-			command.AddParameterWithValue ("@FINGERPRINT", fingerprint);
-
-			command.CommandText = query.ToString ();
-			command.CommandType = CommandType.Text;
-
-			return command;
+			return query.Insert ("SELECT ".Length, "TOP 1 ");
 		}
 
 		/// <summary>

MimeKit/Cryptography/SqlCertificateDatabase.cs

@@ -222,6 +222,19 @@ string GetParameterName (string columnName)
 			return parameterName;
 		}
 
+		/// <summary>
+		/// Limit the query results to a single record.
+		/// </summary>
+		/// <remarks>
+		/// Modifies the SQL <c>SELECT</c> <paramref name="query"/> to limit the query results to a single record.
+		/// </remarks>
+		/// <param name="query">A <see cref="StringBuilder"/> containing an SQL <c>SELECT</c> query.</param>
+		/// <returns>A modified SQL query that will limit the results to a single record.</returns>
+		protected virtual StringBuilder LimitToOne (StringBuilder query)
+		{
+			return query.Append (" LIMIT 1");
+		}
+
 		/// <summary>
 		/// Gets the name of an index based on the table and columns that it is built against.
 		/// </summary>
@@ -400,7 +413,7 @@ void CreateCrlsTable (DbConnection connection, DataTable table)
 		}
 
 		/// <summary>
-		/// Creates a SELECT query string builder for the specified fields of an X.509 certificate record.
+		/// Create a SELECT query string builder for the specified fields of an X.509 certificate record.
 		/// </summary>
 		/// <remarks>
 		/// Creates a SELECT query string builder for the specified fields of an X.509 certificate record.
@@ -423,7 +436,7 @@ protected static StringBuilder CreateSelectQuery (X509CertificateRecordFields fi
 		}
 
 		/// <summary>
-		/// Creates a SELECT query string builder for the specified fields of an X.509 CRL record.
+		/// Create a SELECT query string builder for the specified fields of an X.509 CRL record.
 		/// </summary>
 		/// <remarks>
 		/// Creates a SELECT query string builder for the specified fields of an X.509 CRL record.
@@ -471,7 +484,9 @@ protected override DbCommand GetSelectCommand (DbConnection connection, X509Cert
 			query = query.Append (" WHERE ")
 				.Append (CertificateColumnNames.IssuerName).Append (" = ").Append (issuerNameParameter).Append (" AND ")
 				.Append (CertificateColumnNames.SerialNumber).Append (" = ").Append (serialNumberParameter).Append (" AND ")
-				.Append (CertificateColumnNames.Fingerprint).Append (" = ").Append (fingerprintParameter).Append (" LIMIT 1");
+				.Append (CertificateColumnNames.Fingerprint).Append (" = ").Append (fingerprintParameter);
+			query = LimitToOne (query);
+
 			command.AddParameterWithValue (issuerNameParameter, issuerName);
 			command.AddParameterWithValue (serialNumberParameter, serialNumber);
 			command.AddParameterWithValue (fingerprintParameter, fingerprint);
@@ -734,7 +749,9 @@ protected override DbCommand GetSelectCommand (DbConnection connection, X509Crl
 			var query = CreateSelectQuery (fields).Append (" WHERE ")
 				.Append (CrlColumnNames.Delta).Append (" = ").Append (deltaParameter).Append (" AND ")
 				.Append (CrlColumnNames.IssuerName).Append ("= ").Append (issuerNameParameter).Append (" AND ")
-				.Append (CrlColumnNames.ThisUpdate).Append (" = ").Append (thisUpdateParameter).Append (" LIMIT 1");
+				.Append (CrlColumnNames.ThisUpdate).Append (" = ").Append (thisUpdateParameter);
+			query = LimitToOne (query);
+
 			var issuerName = crl.IssuerDN.ToString ();
 			var command = CreateCommand ();