re-factor SqlExpression sql generation into DialectProvider

Author: mythz

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -521,26 +521,10 @@ public virtual string ToUpdateStatement(T item, bool excludeDefaults = false)
 
         public virtual string ToSelectStatement()
         {
-            var sql = new StringBuilder();
+            var sql = OrmLiteConfig.DialectProvider
+                .ToSelectStatement(modelDef, SelectExpression, BodyExpression, OrderByExpression, Offset, Rows);
 
-            sql.Append(SelectExpression);
-
-            sql.Append(FromExpression);
-
-            sql.Append(string.IsNullOrEmpty(WhereExpression) ?
-                       "" :
-                       "\n" + WhereExpression);
-            sql.Append(string.IsNullOrEmpty(GroupByExpression) ?
-                       "" :
-                       "\n" + GroupByExpression);
-            sql.Append(string.IsNullOrEmpty(HavingExpression) ?
-                       "" :
-                       "\n" + HavingExpression);
-            sql.Append(string.IsNullOrEmpty(OrderByExpression) ?
-                       "" :
-                       "\n" + OrderByExpression);
-
-            return ApplyPaging(sql.ToString());
+            return sql;
         }
 
         public virtual string ToCountStatement()
@@ -573,6 +557,17 @@ public string FromExpression
             set { fromExpression = value; }
         }
 
+        public string BodyExpression
+        {
+            get
+            {
+                return FromExpression
+                    + (string.IsNullOrEmpty(WhereExpression) ? "" : "\n" + WhereExpression)
+                    + (string.IsNullOrEmpty(GroupByExpression) ? "" : "\n" + GroupByExpression)
+                    + (string.IsNullOrEmpty(HavingExpression) ? "" : "\n" + HavingExpression);
+            }
+        }
+
         public string WhereExpression
         {
             get
@@ -622,19 +617,6 @@ public string OrderByExpression
             }
         }
 
-        public virtual string LimitExpression
-        {
-            get
-            {
-                if (Offset == null && Rows == null)
-                    return "";
-
-                return Offset == null
-                    ? "LIMIT " + Rows
-                    : "LIMIT " + Rows.GetValueOrDefault(int.MaxValue) + " OFFSET " + Offset;
-            }
-        }
-
         public int? Rows { get; set; }
         public int? Offset { get; set; }
 
@@ -1123,13 +1105,6 @@ public IList<string> GetAllFields()
             return modelDef.FieldDefinitions.ConvertAll(r => r.Name);
         }
 
-        protected virtual string ApplyPaging(string sql)
-        {
-            var limitExpression = LimitExpression;
-            sql = sql + (string.IsNullOrEmpty(limitExpression) ? "" : "\n" + limitExpression);
-            return sql;
-        }
-
         private bool IsStaticArrayMethod(MethodCallExpression m)
         {
             if (m.Object == null && m.Method.Name == "Contains")

src/ServiceStack.OrmLite/IOrmLiteDialectProvider.cs

@@ -74,6 +74,8 @@ string GetColumnDefinition(
 
         string ToSelectStatement(Type tableType, string sqlFilter, params object[] filterParams);
 
+        string ToSelectStatement(ModelDefinition modelDef, string selectExpression, string bodyExpression, string orderByExpression = null, int? offset = null, int? rows = null);
+
         string ToInsertRowStatement(IDbCommand command, object objWithProperties, ICollection<string> InsertFields = null);
 
         void PrepareParameterizedInsertStatement<T>(IDbCommand cmd, ICollection<string> insertFields = null);

src/ServiceStack.OrmLite/OrmLiteDialectProviderBase.cs

@@ -476,6 +476,37 @@ public virtual string ToSelectStatement(Type tableType, string sqlFilter, params
             return sql.ToString();
         }
 
+        public virtual string ToSelectStatement(ModelDefinition modelDef, 
+            string selectExpression, 
+            string bodyExpression,
+            string orderByExpression = null, 
+            int? offset = null, 
+            int? rows = null)
+        {
+
+            var sb = new StringBuilder(selectExpression);
+            sb.Append(bodyExpression);
+            if (orderByExpression != null)
+            {
+                sb.Append(orderByExpression);
+            }
+
+            if (offset != null || rows != null)
+            {
+                sb.Append("\nLIMIT ");
+                if (offset == null)
+                {
+                    sb.Append(rows);
+                }
+                else
+                {
+                    sb.Append(rows.GetValueOrDefault(int.MaxValue)).Append(" OFFSET ").Append(offset);
+                }
+            }
+
+            return sb.ToString();
+        }
+
         public virtual string GetRowVersionColumnName(FieldDefinition field)
         {
             return GetQuotedColumnName(field.FieldName);