Add OrderBy Random in OrderByFields

Author: mythz

src/ServiceStack.OrmLite.Oracle/OracleOrmLiteDialectProvider.cs

@@ -1129,6 +1129,8 @@ public override string ToRowCountStatement(string innerSql)
         }
 
         public override string SqlConcat(IEnumerable<object> args) => string.Join(" || ", args);
+
+        public override string SqlRandom => "dbms_random.value";
 
         protected OracleConnection Unwrap(IDbConnection db)
         {

src/ServiceStack.OrmLite.PostgreSQL/PostgreSQLDialectProvider.cs

@@ -706,6 +706,8 @@ public override string SqlCurrency(string fieldOrValue, string currencySymbol) =
         public override string SqlCast(object fieldOrValue, string castAs) => 
             $"({fieldOrValue})::{castAs}";
 
+        public override string SqlRandom => "RANDOM()";
+
         protected NpgsqlConnection Unwrap(IDbConnection db)
         {
             return (NpgsqlConnection)db.ToDbConnection();

src/ServiceStack.OrmLite.PostgreSQL/PostgreSqlExpression.cs

@@ -19,11 +19,6 @@ 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

@@ -22,11 +22,6 @@ public override string GetSubstringSql(object quotedColumn, int startIndex, int?
                 : $"substring({quotedColumn}, {startIndex}, LEN({quotedColumn}) - {startIndex} + 1)";
         }
 
-        public override SqlExpression<T> OrderByRandom()
-        {
-            return base.OrderBy("NEWID()");
-        }
-
         protected override PartialSqlString ToLengthPartialString(object arg)
         {
             return new PartialSqlString($"LEN({arg})");

src/ServiceStack.OrmLite.SqlServer/SqlServerOrmLiteDialectProvider.cs

@@ -648,6 +648,8 @@ public override string SqlCast(object fieldOrValue, string castAs) =>
                 ? $"CAST({fieldOrValue} AS VARCHAR(MAX))"
                 : $"CAST({fieldOrValue} AS {castAs})";
 
+        public override string SqlRandom => "NEWID()";
+        
         protected SqlConnection Unwrap(IDbConnection db) => (SqlConnection)db.ToDbConnection();
 
         protected SqlCommand Unwrap(IDbCommand cmd) => (SqlCommand)cmd.ToDbCommand();

src/ServiceStack.OrmLite.Sqlite/SqliteExpression.cs

@@ -70,11 +70,6 @@ protected override object VisitSqlMethodCall(MethodCallExpression m)
             return new PartialSqlString(statement);
         }
 
-        public override SqlExpression<T> OrderByRandom()
-        {
-            return base.OrderBy("random()");
-        }
-
         protected override PartialSqlString ToLengthPartialString(object arg)
         {
             return new PartialSqlString($"LENGTH({arg})");

src/ServiceStack.OrmLite.Sqlite/SqliteOrmLiteDialectProviderBase.cs

@@ -243,6 +243,8 @@ public override string SqlConflict(string sql, string conflictResolution)
         public override string SqlCurrency(string fieldOrValue, string currencySymbol) => SqlConcat(new []{ "'" + currencySymbol + "'", "printf(\"%.2f\", " + fieldOrValue + ")" });
 
         public override string SqlBool(bool value) => value ? "1" : "0";
+
+        public override string SqlRandom => "random()";
     }
 
     public static class SqliteExtensions

src/ServiceStack.OrmLite/Expressions/SqlExpression.cs

@@ -795,7 +795,7 @@ public virtual SqlExpression<T> UnsafeOrderBy(string orderBy)
 
         public virtual SqlExpression<T> OrderByRandom()
         {
-            return OrderBy("RAND()");
+            return OrderBy(DialectProvider.SqlRandom);
         }
 
         public ModelDefinition GetModelDefinition(FieldDefinition fieldDef)
@@ -875,9 +875,11 @@ private SqlExpression<T> OrderByFields(string orderBySuffix, string[] fieldNames
                 var useName = reverse ? fieldName.Substring(1) : fieldName;
 
                 var field = FirstMatchingField(useName);
-                if (field == null)
-                    throw new ArgumentException("Could not find field " + useName);
-                var qualifiedName = GetQuotedColumnName(field.Item1, field.Item2.Name);
+                var qualifiedName = field != null
+                    ? GetQuotedColumnName(field.Item1, field.Item2.Name)
+                    : string.Equals("Random", useName)
+                        ? DialectProvider.SqlRandom
+                        : throw new ArgumentException("Could not find field " + useName);
 
                 if (sbOrderBy.Length > 0)
                     sbOrderBy.Append(", ");

src/ServiceStack.OrmLite/IOrmLiteDialectProvider.cs

@@ -239,7 +239,7 @@ string ToCreateIndexStatement<T>(Expression<Func<T, object>> field,
         /// <summary>
         /// Return table, row count SQL for listing all tables with their row counts
         /// </summary>
-        /// <param name="live">If true returns live current rowc ounts of each table (slower), otherwise returns cached row counts from RDBMS table stats</param>
+        /// <param name="live">If true returns live current row counts of each table (slower), otherwise returns cached row counts from RDBMS table stats</param>
         /// <param name="schema">The table schema if any</param>
         /// <returns></returns>
         string ToTableNamesWithRowCountsStatement(bool live, string schema);
@@ -252,5 +252,6 @@ string ToCreateIndexStatement<T>(Expression<Func<T, object>> field,
         string SqlBool(bool value);
         string SqlLimit(int? offset = null, int? rows = null);
         string SqlCast(object fieldOrValue, string castAs);
+        string SqlRandom { get; }
     }
 }

src/ServiceStack.OrmLite/OrmLiteDialectProviderBase.cs

@@ -1668,7 +1668,9 @@ public virtual string SqlLimit(int? offset = null, int? rows = null) => rows ==
 
         public virtual string SqlCast(object fieldOrValue, string castAs) => $"CAST({fieldOrValue} AS {castAs})";
 
-        //Async API's, should be overrided by Dialect Providers to use .ConfigureAwait(false)
+        public virtual string SqlRandom => "RAND()";
+
+        //Async API's, should be overriden by Dialect Providers to use .ConfigureAwait(false)
         //Default impl below uses TaskAwaiter shim in async.cs
 
         public virtual Task OpenAsync(IDbConnection db, CancellationToken token = default)