Merge remote-tracking branch 'origin/v8/dev' into netcore/dev

# Conflicts:
#	src/Umbraco.Core/Services/UserServiceExtensions.cs
#	src/Umbraco.Infrastructure/Examine/ContentValueSetBuilder.cs
#	src/Umbraco.Infrastructure/Runtime/SqlMainDomLock.cs
#	src/Umbraco.Infrastructure/Search/ExamineComposer.cs
#	src/Umbraco.PublishedCache.NuCache/DataSource/DatabaseDataSource.cs
#	src/Umbraco.Tests/UmbracoExamine/IndexInitializer.cs

src/Umbraco.Infrastructure/Persistence/NPocoDatabaseExtensions.cs

@@ -15,6 +15,48 @@ namespace Umbraco.Core.Persistence
     /// </summary>
     public static partial class NPocoDatabaseExtensions
     {
+        /// <summary>
+        /// Iterates over the result of a paged data set with a db reader
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="database"></param>
+        /// <param name="pageSize">
+        /// The number of rows to load per page
+        /// </param>
+        /// <param name="sql"></param>
+        /// <returns></returns>
+        /// <remarks>
+        /// NPoco's normal Page returns a List{T} but sometimes we don't want all that in memory and instead want to
+        /// iterate over each row with a reader using Query vs Fetch.
+        /// </remarks>
+        public static IEnumerable<T> QueryPaged<T>(this IDatabase database, long pageSize, Sql sql)
+        {
+            var sqlString = sql.SQL;
+            var sqlArgs = sql.Arguments;
+
+            int? itemCount = null;
+            long pageIndex = 0;
+            do
+            {
+                // Get the paged queries
+                database.BuildPageQueries<T>(pageIndex * pageSize, pageSize, sqlString, ref sqlArgs, out var sqlCount, out var sqlPage);
+
+                // get the item count once
+                if (itemCount == null)
+                {
+                    itemCount = database.ExecuteScalar<int>(sqlCount, sqlArgs);
+                }
+                pageIndex++;
+
+                // iterate over rows without allocating all items to memory (Query vs Fetch)
+                foreach (var row in database.Query<T>(sqlPage, sqlArgs))
+                {
+                    yield return row;
+                }
+
+            } while ((pageIndex * pageSize) < itemCount);
+        }
+
         // NOTE
         //
         // proper way to do it with TSQL and SQLCE