Update the docs

docs/en/table_engines/aggregatingmergetree.md

@@ -40,7 +40,7 @@ SELECT uniq(UserID) FROM table
 SELECT uniqMerge(state) FROM (SELECT uniqState(UserID) AS state FROM table GROUP BY RegionID)
 ```
 
-There is an ` AggregatingMergeTree` engine. Its job during a merge is to combine the states of aggregate functions from different table rows with the same primary key value.
+There is an `AggregatingMergeTree` engine. Its job during a merge is to combine the states of aggregate functions from different table rows with the same primary key value.
 
 You can't use a normal INSERT to insert a row in a table containing `AggregateFunction` columns, because you can't explicitly define the `AggregateFunction` value. Instead, use `INSERT SELECT` with `-State` aggregate functions for inserting data.
 

docs/en/table_engines/summingmergetree.md

@@ -16,7 +16,7 @@ The columns to total are set explicitly (the last parameter – Shows, Clicks, C
 
 If the values were null in all of these columns, the row is deleted. (The exception is cases when the data part would not have any rows left in it.)
 
-For the other rows that are not part of the primary key, the first value that occurs is selected when merging.
+For the other columns that are not part of the primary key, the first value that occurs is selected when merging. But if a column is of AggregateFunction type, then it is merged according to that function, which effectively makes this engine behave like `AggregatingMergeTree`.
 
 Summation is not performed for a read operation. If it is necessary, write the appropriate GROUP BY.
 

docs/ru/table_engines/summingmergetree.md

@@ -16,7 +16,7 @@ SummingMergeTree(EventDate, (OrderID, EventDate, BannerID, ...), 8192, (Shows, C
 
 Если значения во всех таких столбцах оказались нулевыми, то строчка удаляется. (За исключением случаев, когда в куске данных не осталось бы ни одной строчки.)
 
-Для остальных столбцов, не входящих в первичный ключ, при слиянии выбирается первое попавшееся значение.
+Для остальных столбцов, не входящих в первичный ключ, при слиянии выбирается первое попавшееся значение. Но для столбцов типа AggregateFunction выполняется агрегация согласно заданной функции, так что этот движок фактически ведёт себя как `AggregatinMergeTree`.
 
 При чтении, суммирование не делается само по себе. Если оно необходимо - напишите соответствующий GROUP BY.