Fixed error with Arrays inside Nested data type; added a test #2066

dbms/src/DataTypes/IDataType.cpp

@@ -70,8 +70,13 @@ size_t IDataType::getSizeOfValueInMemory() const
 
 String IDataType::getFileNameForStream(const String & column_name, const IDataType::SubstreamPath & path)
 {
+    /// Sizes of arrays (elements of Nested type) are shared (all reside in single file).
     String nested_table_name = Nested::extractTableName(column_name);
-    bool is_sizes_of_nested_type = !path.empty() && path.back().type == IDataType::Substream::ArraySizes
+
+    bool is_sizes_of_nested_type =
+        path.size() == 1    /// Nested structure may have arrays as nested elements (so effectively we have multidimentional arrays).
+                            /// Sizes of arrays are shared only at first level.
+        && path[0].type == IDataType::Substream::ArraySizes
         && nested_table_name != column_name;
 
     size_t array_level = 0;

dbms/src/Storages/MergeTree/MergeTreeReader.cpp

@@ -365,7 +365,7 @@ void MergeTreeReader::readData(
     IDataType::InputStreamGetter stream_getter = [&] (const IDataType::SubstreamPath & path) -> ReadBuffer *
     {
         /// If offsets for arrays have already been read.
-        if (!with_offsets && !path.empty() && path.back().type == IDataType::Substream::ArraySizes)
+        if (!with_offsets && path.size() == 1 && path[0].type == IDataType::Substream::ArraySizes)
             return nullptr;
 
         String stream_name = IDataType::getFileNameForStream(name, path);

dbms/src/Storages/MergeTree/MergedBlockOutputStream.h

@@ -150,6 +150,7 @@ private:
 class MergedColumnOnlyOutputStream final : public IMergedBlockOutputStream
 {
 public:
+    /// skip_offsets: used when ALTERing columns if we know that array offsets are not altered.
     MergedColumnOnlyOutputStream(
         MergeTreeData & storage_, const Block & header_, String part_path_, bool sync_, CompressionSettings compression_settings, bool skip_offsets_);
 

dbms/tests/queries/0_stateless/00625_arrays_in_nested.reference

@@ -0,0 +1,5 @@
+['Hello','World']	[['a'],['b','c']]	[['PU','US'],['OTHER']]
+['Hello','World']	[['a'],['b','c']]	[['PU','US'],['OTHER']]
+['Hello','World']	[['a'],['b','c']]	[['PU','US'],['OTHER']]
+['Hello','World']	[['a'],['b','c']]	[['PU','US'],['OTHER']]
+['Hello','World']	[['a'],['b','c']]	[['PU','US'],['OTHER']]

dbms/tests/queries/0_stateless/00625_arrays_in_nested.sql

@@ -0,0 +1,83 @@
+USE test;
+
+DROP TABLE IF EXISTS nested;
+CREATE TABLE nested
+(
+    column Nested
+    (
+        name String,
+        names Array(String),
+        types Array(Enum8('PU' = 1, 'US' = 2, 'OTHER' = 3))
+    )
+) ENGINE = MergeTree ORDER BY tuple();
+
+INSERT INTO nested VALUES (['Hello', 'World'], [['a'], ['b', 'c']], [['PU', 'US'], ['OTHER']]);
+
+SELECT * FROM nested;
+
+
+DROP TABLE IF EXISTS nested;
+CREATE TABLE nested
+(
+    column Nested
+    (
+        name String,
+        names Array(String),
+        types Array(Enum8('PU' = 1, 'US' = 2, 'OTHER' = 3))
+    )
+) ENGINE = Log;
+
+INSERT INTO nested VALUES (['Hello', 'World'], [['a'], ['b', 'c']], [['PU', 'US'], ['OTHER']]);
+
+SELECT * FROM nested;
+
+
+DROP TABLE IF EXISTS nested;
+CREATE TABLE nested
+(
+    column Nested
+    (
+        name String,
+        names Array(String),
+        types Array(Enum8('PU' = 1, 'US' = 2, 'OTHER' = 3))
+    )
+) ENGINE = TinyLog;
+
+INSERT INTO nested VALUES (['Hello', 'World'], [['a'], ['b', 'c']], [['PU', 'US'], ['OTHER']]);
+
+SELECT * FROM nested;
+
+
+DROP TABLE IF EXISTS nested;
+CREATE TABLE nested
+(
+    column Nested
+    (
+        name String,
+        names Array(String),
+        types Array(Enum8('PU' = 1, 'US' = 2, 'OTHER' = 3))
+    )
+) ENGINE = StripeLog;
+
+INSERT INTO nested VALUES (['Hello', 'World'], [['a'], ['b', 'c']], [['PU', 'US'], ['OTHER']]);
+
+SELECT * FROM nested;
+
+
+DROP TABLE IF EXISTS nested;
+CREATE TABLE nested
+(
+    column Nested
+    (
+        name String,
+        names Array(String),
+        types Array(Enum8('PU' = 1, 'US' = 2, 'OTHER' = 3))
+    )
+) ENGINE = Memory;
+
+INSERT INTO nested VALUES (['Hello', 'World'], [['a'], ['b', 'c']], [['PU', 'US'], ['OTHER']]);
+
+SELECT * FROM nested;
+
+
+DROP TABLE nested;