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functions-and-operators/group-by-modifier.md

@@ -170,7 +170,7 @@ SELECT year, month, SUM(profit) AS profit, grouping(year) as grp_year, grouping(
 
 ## How to interpret the ROLLUP execution plan
 
-Multidimensional data aggregation uses the `Expand` operator to copy data to meet the needs of multidimensional grouping. Each data copy corresponds to a grouping of a specific dimension. In MPP mode, the `Expand` operator can facilitate data shuffle to quickly reorganize and calculate a large amount of data between multiple nodes, making full use of the computing capacity of each node; In a TiDB cluster without TiFlash nodes, because the `Expand` operator is only executed on a single TiDB node, data redundancy will increase as the number of dimension groupings (`grouping set`) increases.
+Multidimensional data aggregation uses the `Expand` operator to copy data to meet the needs of multidimensional grouping. Each data copy corresponds to a grouping of a specific dimension. In MPP mode, the `Expand` operator can facilitate data shuffle to quickly reorganize and calculate a large amount of data between multiple nodes, making full use of the computing capacity of each node. In a TiDB cluster without TiFlash nodes, because the `Expand` operator is only executed on a single TiDB node, data redundancy will increase as the number of dimension groupings (`grouping set`) increases.
 
 The implementation of the `Expand` operator is similar to that of the `Projection` operator. The difference is that `Expand` is a multi-level `Projection`, which contains multiple levels of projection operation expressions. For each row of the raw data, the `Projection` operator generates only one row in results, whereas the `Expand` operator generates multiple rows in results (the number of rows is equal to the number of levels in projection operation expressions).