Merge pull request ClickHouse#91498 from ClickHouse/backport/25.8/90927

Backport ClickHouse#90927 to 25.8: Fix SummingMergeTree aggregation for Nested LowCardinality columns

Author: clickhouse-gh[bot]

src/Processors/Merges/Algorithms/SummingSortedAlgorithm.cpp

@@ -415,7 +415,7 @@ static SummingSortedAlgorithm::ColumnsDefinition defineColumns(
         {
             const ColumnWithTypeAndName & key_col = header.safeGetByPosition(*column_num_it);
             const String & name = key_col.name;
-            const IDataType & nested_type = *assert_cast<const DataTypeArray &>(*key_col.type).getNestedType();
+            const IDataType & nested_type = *recursiveRemoveLowCardinality(assert_cast<const DataTypeArray &>(*key_col.type).getNestedType());
 
             if (column_num_it == map.second.begin()
                 || endsWith(name, "ID")

tests/queries/0_stateless/03733_summing_merge_tree_nested_low_cardinality.reference

@@ -0,0 +1 @@
+lol	10	['a','b']	[4,6]

tests/queries/0_stateless/03733_summing_merge_tree_nested_low_cardinality.sql

@@ -0,0 +1,8 @@
+CREATE TABLE sums (key LowCardinality(String), sumOfSums UInt64, sumsMap Nested (key LowCardinality(String), sum UInt64)) ENGINE = SummingMergeTree PRIMARY KEY (key);
+
+INSERT INTO sums (key, sumOfSums, sumsMap.key, sumsMap.sum) VALUES ('lol', 3, ['a', 'b'], [1, 2]);
+INSERT INTO sums (key, sumOfSums, sumsMap.key, sumsMap.sum) VALUES ('lol', 7, ['a', 'b'], [3, 4]);
+
+OPTIMIZE TABLE sums;
+
+SELECT * FROM sums;