Add support for OrderByRandon() to all RDBMS providers

Author: mythz

src/ServiceStack.OrmLite.Oracle/OracleSqlExpression.cs

@@ -42,6 +42,11 @@ protected override void ConvertToPlaceholderAndParameter(ref object right)
 
             right = parameter.ParameterName;
         }
+
+        public override SqlExpression<T> OrderByRandom()
+        {
+            return base.OrderBy("dbms_random.value");
+        }
     }
 }
 

src/ServiceStack.OrmLite.PostgreSQL/PostgreSqlExpression.cs

@@ -21,5 +21,10 @@ protected override string GetQuotedColumnName(ModelDefinition tableDef, string m
             }
             return memberName;
         }
+
+        public override SqlExpression<T> OrderByRandom()
+        {
+            return base.OrderBy("RANDOM()");
+        }
     }
 }

src/ServiceStack.OrmLite.SqlServer/SqlServerExpression.cs

@@ -49,5 +49,10 @@ public override string GetSubstringSql(object quotedColumn, int startIndex, int?
                 ? string.Format("substring({0}, {1}, {2})", quotedColumn, startIndex, length.Value)
                 : string.Format("substring({0}, {1}, LEN({0}) - {1} + 1)", quotedColumn, startIndex );
         }
-    }
+
+	    public override SqlExpression<T> OrderByRandom()
+	    {
+	        return base.OrderBy("NEWID()");
+	    }
+	}
 }

src/ServiceStack.OrmLite.Sqlite/SqliteExpression.cs

@@ -74,5 +74,10 @@ protected override object VisitSqlMethodCall(MethodCallExpression m)
 
             return new PartialSqlString(statement);
         }
+
+        public override SqlExpression<T> OrderByRandom()
+        {
+            return base.OrderBy("random()");
+        }
     }
 }

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -356,6 +356,11 @@ public virtual SqlExpression<T> OrderBy(string orderBy)
             return this;
         }
 
+        public virtual SqlExpression<T> OrderByRandom()
+        {
+            return OrderBy("RAND()");
+        }
+
         public ModelDefinition GetModelDefinition(FieldDefinition fieldDef)
         {
             if (modelDef.FieldDefinitions.Any(x => x == fieldDef))

tests/ServiceStack.OrmLite.Tests/OrderByTests.cs

@@ -0,0 +1,33 @@
+using System.Linq;
+using NUnit.Framework;
+using ServiceStack.Common.Tests.Models;
+using ServiceStack.OrmLite.Tests.Expression;
+using ServiceStack.Text;
+
+namespace ServiceStack.OrmLite.Tests
+{
+    [TestFixture]
+    public class OrderByTests : OrmLiteTestBase
+    {
+        [Test]
+        public void Can_order_by_random()
+        {
+            using (var db = OpenDbConnection())
+            {
+                db.DropAndCreateTable<LetterFrequency>();
+
+                10.Times(i => db.Insert(new LetterFrequency { Letter = ('A' + i).ToString() }));
+
+                var rowIds1 = db.Select<LetterFrequency>(q => q.OrderBy(x => x.Id)).Map(x => x.Id);
+                var rowIds2 = db.Select<LetterFrequency>(q => q.OrderBy(x => x.Id)).Map(x => x.Id);
+
+                Assert.That(rowIds1.SequenceEqual(rowIds2));
+
+                rowIds1 = db.Select<LetterFrequency>(q => q.OrderByRandom()).Map(x => x.Id);
+                rowIds2 = db.Select<LetterFrequency>(q => q.OrderByRandom()).Map(x => x.Id);
+
+                Assert.That(!rowIds1.SequenceEqual(rowIds2));
+            }
+        }
+    }
+}

tests/ServiceStack.OrmLite.Tests/ServiceStack.OrmLite.Tests.csproj

@@ -161,6 +161,7 @@
     <Compile Include="LoggingTests.cs" />
     <Compile Include="MergeTests.cs" />
     <Compile Include="MockAllApiTests.cs" />
+    <Compile Include="OrderByTests.cs" />
     <Compile Include="OrmLiteContextTests.cs" />
     <Compile Include="OrmLiteExecFilterTests.cs" />
     <Compile Include="OrmLiteFiltersTests.cs" />