Add column statistics for table system.columns

src/Storages/StatisticsDescription.cpp

@@ -213,4 +213,20 @@ ASTPtr ColumnStatisticsDescription::getAST() const
     return function_node;
 }
 
+String ColumnStatisticsDescription::getNameForLogs() const
+{
+    String ret;
+    for (const auto & [tp, desc] : types_to_desc)
+    {
+        ret += desc.getTypeName();
+        if (desc.is_implicit)
+            ret += "(auto)";
+        ret += ",";
+    }
+    if (!ret.empty())
+        ret.pop_back();
+    return ret;
+}
+
+
 }

src/Storages/StatisticsDescription.h

@@ -58,6 +58,8 @@ struct ColumnStatisticsDescription
 
     ASTPtr getAST() const;
 
+    String getNameForLogs() const;
+
     /// get a vector of <column name, statistics desc> pair
     static std::vector<std::pair<String, ColumnStatisticsDescription>> fromAST(const ASTPtr & definition_ast, const ColumnsDescription & columns);
     static ColumnStatisticsDescription fromStatisticsDescriptionAST(const ASTPtr & statistics_desc, const String & column_name, DataTypePtr data_type);

src/Storages/System/StorageSystemColumns.cpp

@@ -69,6 +69,7 @@ StorageSystemColumns::StorageSystemColumns(const StorageID & table_id_)
         { "datetime_precision",         std::make_shared<DataTypeNullable>(std::make_shared<DataTypeUInt64>()),
             "Decimal precision of DateTime64 data type. For other data types, the NULL value is returned."},
         { "serialization_hint",         std::make_shared<DataTypeNullable>(std::make_shared<DataTypeString>()), "A hint for column to choose serialization on inserts according to statistics."},
+        { "statistics",                 std::make_shared<DataTypeString>(), "The types of statistics created in this columns."}
     });
 
     description.setAliases({
@@ -331,6 +332,13 @@ class ColumnsSource : public ISource
                         res_columns[res_index++]->insertDefault();
                 }
 
+                /// statistics
+                if (columns_mask[src_index++])
+                {
+                    const ColumnStatisticsDescription & stats = column.statistics;
+                    res_columns[res_index++]->insert(stats.getNameForLogs());
+                }
+
                 ++rows_count;
             }
         }

tests/queries/0_stateless/01602_temporary_table_in_system_tables.reference

@@ -1,8 +1,8 @@
 	test_01602a	CREATE TEMPORARY TABLE test_01602a (`x` UInt32) ENGINE = Memory	Memory	Memory	1
 	test_01602b	CREATE TEMPORARY TABLE test_01602b (`y` Float64, `z` String) ENGINE = Memory	Memory	Memory	1
-	test_01602a	x	UInt32	1			0	0	0		0	0	0	0		\N	32	2	0	\N	\N
-	test_01602b	y	Float64	1			0	0	0		0	0	0	0		\N	\N	\N	\N	\N	\N
-	test_01602b	z	String	2			0	0	0		0	0	0	0		\N	\N	\N	\N	\N	\N
+	test_01602a	x	UInt32	1			0	0	0		0	0	0	0		\N	32	2	0	\N	\N	
+	test_01602b	y	Float64	1			0	0	0		0	0	0	0		\N	\N	\N	\N	\N	\N	
+	test_01602b	z	String	2			0	0	0		0	0	0	0		\N	\N	\N	\N	\N	\N	
 CREATE TEMPORARY TABLE test_01602a\n(\n    `x` UInt32\n)\nENGINE = Memory
 CREATE TEMPORARY TABLE test_01602b\n(\n    `y` Float64,\n    `z` String\n)\nENGINE = Memory
 0

tests/queries/0_stateless/02117_show_create_table_system.reference

@@ -92,6 +92,7 @@ CREATE TABLE system.columns
     `numeric_scale` Nullable(UInt64),
     `datetime_precision` Nullable(UInt64),
     `serialization_hint` Nullable(String),
+    `statistics` String,
     `column` String ALIAS name
 )
 ENGINE = SystemColumns