String parameters in queries to varchar (not blob) directly (#89)

Author: cincuranet

Provider/src/FirebirdSql.EntityFrameworkCore.Firebird/Query/Sql/Internal/FbQuerySqlGenerator.cs

@@ -111,7 +111,22 @@ protected override Expression VisitParameter(ParameterExpression parameterExpres
 			if (_fbOptions.ExplicitParameterTypes)
 			{
 				Sql.Append(" AS ");
-				Sql.Append(Dependencies.TypeMappingSource.GetMapping(parameterExpression.Type).StoreType);
+				if (parameterExpression.Type == typeof(string))
+				{
+					if (ParameterValues.TryGetValue(parameterExpression.Name, out var parameterValue))
+					{
+						Sql.Append(((IFbTypeMappingSource)Dependencies.TypeMappingSource).StringParameterQueryType((string)parameterValue));
+						IsCacheable = false;
+					}
+					else
+					{
+						Sql.Append(((IFbTypeMappingSource)Dependencies.TypeMappingSource).StringParameterQueryType());
+					}
+				}
+				else
+				{
+					Sql.Append(Dependencies.TypeMappingSource.GetMapping(parameterExpression.Type).StoreType);
+				}
 				Sql.Append(")");
 			}
 			return parameterExpression;
@@ -173,17 +188,16 @@ protected override string GenerateOperator(Expression expression)
 		protected override Expression VisitConstant(ConstantExpression constantExpression)
 		{
 			var svalue = constantExpression.Value as string;
-			var explicitVarcharPossible = constantExpression.Type == typeof(string) && svalue?.Length > 0;
-			if (_fbOptions.ExplicitStringLiteralTypes && explicitVarcharPossible)
+			if (_fbOptions.ExplicitStringLiteralTypes && constantExpression.Type == typeof(string))
 			{
 				Sql.Append("CAST(");
 			}
 			base.VisitConstant(constantExpression);
-			if (_fbOptions.ExplicitStringLiteralTypes && explicitVarcharPossible)
+			if (_fbOptions.ExplicitStringLiteralTypes && constantExpression.Type == typeof(string))
 			{
-				Sql.Append(" AS VARCHAR(");
-				Sql.Append(svalue.Length);
-				Sql.Append(") CHARACTER SET UTF8)");
+				Sql.Append(" AS ");
+				Sql.Append(((IFbTypeMappingSource)Dependencies.TypeMappingSource).StringLiteralQueryType(svalue));
+				Sql.Append(")");
 			}
 			return constantExpression;
 		}

Provider/src/FirebirdSql.EntityFrameworkCore.Firebird/Storage/Internal/FbTypeMappingSource.cs

@@ -24,7 +24,7 @@
 
 namespace FirebirdSql.EntityFrameworkCore.Firebird.Storage.Internal
 {
-	public class FbTypeMappingSource : RelationalTypeMappingSource
+	public class FbTypeMappingSource : RelationalTypeMappingSource, IFbTypeMappingSource
 	{
 		public const int BinaryMaxSize = Int32.MaxValue;
 		public const int VarcharMaxSize = 32765 / 4;
@@ -190,5 +190,38 @@ RelationalTypeMapping FindRawMapping(RelationalTypeMappingInfo mappingInfo)
 
 			return null;
 		}
+
+		public virtual string StringLiteralQueryType(string s)
+		{
+			var length = MinimumStringQueryTypeLength(s);
+			EnsureStringQueryTypeLength(length);
+			return $"VARCHAR({length}) CHARACTER SET UTF8";
+		}
+
+		public virtual string StringParameterQueryType(string s)
+		{
+			var length = MinimumStringQueryTypeLength(s);
+			EnsureStringQueryTypeLength(length);
+			return $"VARCHAR({length})";
+		}
+
+		public virtual string StringParameterQueryType()
+		{
+			return $"VARCHAR({VarcharMaxSize})";
+		}
+
+		static int MinimumStringQueryTypeLength(string s)
+		{
+			var length = s?.Length ?? 0;
+			if (length == 0)
+				length = 1;
+			return length;
+		}
+
+		static void EnsureStringQueryTypeLength(int length)
+		{
+			if (length > VarcharMaxSize)
+				throw new ArgumentOutOfRangeException(nameof(length));
+		}
 	}
 }

Provider/src/FirebirdSql.EntityFrameworkCore.Firebird/Storage/Internal/IFbTypeMappingSource.cs

@@ -0,0 +1,28 @@
+/*
+ *    The contents of this file are subject to the Initial
+ *    Developer's Public License Version 1.0 (the "License");
+ *    you may not use this file except in compliance with the
+ *    License. You may obtain a copy of the License at
+ *    https://github.com/FirebirdSQL/NETProvider/blob/master/license.txt.
+ *
+ *    Software distributed under the License is distributed on
+ *    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either
+ *    express or implied. See the License for the specific
+ *    language governing rights and limitations under the License.
+ *
+ *    All Rights Reserved.
+ */
+
+//$Authors = Jiri Cincura ([email protected])
+
+using Microsoft.EntityFrameworkCore.Storage;
+
+namespace FirebirdSql.EntityFrameworkCore.Firebird.Storage.Internal
+{
+	public interface IFbTypeMappingSource : IRelationalTypeMappingSource
+	{
+		string StringLiteralQueryType(string s);
+		string StringParameterQueryType(string s);
+		string StringParameterQueryType();
+	}
+}