Update docs

Author: mythz

README.md

@@ -411,6 +411,16 @@ var q = db.From<Person>()
 db.UpdateOnly(new Person { FirstName = "JJ", LastName = "Hendo" }, onlyFields: q);
 ```
 
+Using an Object Dictionary:
+
+```csharp
+var updateFields = new Dictionary<string,object> {
+    [nameof(Person.FirstName)] = "JJ",
+};
+
+db.UpdateOnly<Person>(updateFields, p => p.LastName == "Hendrix");
+```
+
 Using a typed SQL Expression:
 
 ```csharp
@@ -2107,22 +2117,32 @@ public class PocoTable
 
     [CustomField("DECIMAL(18,4)")]
     public decimal? DecimalColumn { get; set; }
+
+    [CustomField(OrmLiteVariables.MaxText)]        //= {MAX_TEXT}
+    public string MaxText { get; set; }
+
+    [CustomField(OrmLiteVariables.MaxTextUnicode)] //= {NMAX_TEXT}
+    public string MaxUnicodeText { get; set; }
 }
 
 db.CreateTable<PocoTable>(); 
 ```
 
-Generates and executes the following SQL:
+Generates and executes the following SQL in SQL Server:
 
 ```sql
 CREATE TABLE "PocoTable" 
 (
   "Id" INTEGER PRIMARY KEY, 
   "CharColumn" CHAR(20) NULL, 
-  "DecimalColumn" DECIMAL(18,4) NULL 
-);  
+  "DecimalColumn" DECIMAL(18,4) NULL, 
+  "MaxText" VARCHAR(MAX) NULL, 
+  "MaxUnicodeText" NVARCHAR(MAX) NULL 
+); 
 ```
 
+> OrmLite replaces any variable placeholders with the value in each RDBMS DialectProvider's `Variables` Dictionary.
+
 #### Pre / Post Custom SQL Hooks when Creating and Dropping tables 
 
 Pre / Post Custom SQL Hooks allow you to inject custom SQL before and after tables are created or dropped, e.g:
@@ -2877,6 +2897,30 @@ public class Table
 }
 ```
 
+### Bitwise operators
+
+The Typed SqlExpression bitwise operations support depends on the RDBMS used.
+
+E.g. all RDBMS's support Bitwise `And` and `Or` operators:
+
+```csharp
+db.Select<Table>(x => (x.Id | 2) == 3);
+db.Select<Table>(x => (x.Id & 2) == 2);
+```
+
+All RDBMS Except for SQL Server support bit shift operators:
+
+```csharp
+db.Select<Table>(x => (x.Id << 1) == 4);
+db.Select<Table>(x => (x.Id >> 1) == 1);
+```
+
+Whilst only SQL Server and MySQL Support Exclusive Or:
+
+```csharp
+db.Select<Table>(x => (x.Id ^ 2) == 3);
+```
+
 ## SQL Server Features
 
 ### Memory Optimized Tables

tests/ServiceStack.OrmLite.Tests/CustomSqlTests.cs

@@ -17,6 +17,12 @@ public class PocoTable
 
         [CustomField("DECIMAL(18,4)")]
         public decimal? DecimalColumn { get; set; }
+
+        [CustomField(OrmLiteVariables.MaxText)]        //= {MAX_TEXT}
+        public string MaxText { get; set; }
+
+        [CustomField(OrmLiteVariables.MaxTextUnicode)] //= {NMAX_TEXT}
+        public string MaxUnicodeText { get; set; }
     }
 
     [PreCreateTable("CREATE INDEX udxNoTable on NonExistingTable (Name);")]
@@ -71,6 +77,8 @@ public class CustomSqlTests
         [Test]
         public void Can_create_field_with_custom_sql()
         {
+            OrmLiteConfig.BeforeExecFilter = cmd => cmd.GetDebugString().Print();
+            
             using (var db = OpenDbConnection())
             {
                 db.DropAndCreateTable<PocoTable>();