fix reading with evaluated defaults [#CLICKHOUSE-3663]

dbms/src/Storages/MergeTree/MergeTreeBaseBlockInputStream.cpp

@@ -216,7 +216,7 @@ Block MergeTreeBaseBlockInputStream::readFromPart()
             }
 
             progressImpl({ res.rows(), res.bytes() });
-            pre_reader->fillMissingColumns(res, task->ordered_names, task->should_reorder);
+            pre_reader->fillMissingColumns(res, task->ordered_names, task->should_reorder, res.rows());
 
             /// Compute the expression in PREWHERE.
             prewhere_actions->execute(res);
@@ -396,7 +396,7 @@ Block MergeTreeBaseBlockInputStream::readFromPart()
                 ///  as a result of reading components of Nested data structures with no data in filesystem.
                 /// We must fill these arrays to filter them correctly.
 
-                reader->fillMissingColumns(res, task->ordered_names, task->should_reorder);
+                reader->fillMissingColumns(res, task->ordered_names, task->should_reorder, post_filter.size(), true);
 
                 /// Filter the columns related to PREWHERE using pre_filter,
                 ///  other columns - using post_filter.
@@ -422,7 +422,7 @@ Block MergeTreeBaseBlockInputStream::readFromPart()
                 if (task->size_predictor)
                     task->size_predictor->update(res);
 
-                reader->fillMissingColumns(res, task->ordered_names, true);
+                reader->fillMissingColumns(res, task->ordered_names, true, res.rows());
 
                 res.checkNumberOfRows();
             }
@@ -464,7 +464,7 @@ Block MergeTreeBaseBlockInputStream::readFromPart()
             return res;
 
         progressImpl({ res.rows(), res.bytes() });
-        reader->fillMissingColumns(res, task->ordered_names, task->should_reorder);
+        reader->fillMissingColumns(res, task->ordered_names, task->should_reorder, res.rows());
     }
 
     return res;

dbms/src/Storages/MergeTree/MergeTreeReader.cpp

@@ -413,7 +413,8 @@ static bool arrayHasNoElementsRead(const IColumn & column)
 }
 
 
-void MergeTreeReader::fillMissingColumns(Block & res, const Names & ordered_names, bool always_reorder)
+void MergeTreeReader::fillMissingColumns(Block & res, const Names & ordered_names, bool always_reorder,
+                                         size_t rows, bool never_evaluate_defaults)
 {
     if (!res)
         throw Exception("Empty block passed to fillMissingColumns", ErrorCodes::LOGICAL_ERROR);
@@ -444,8 +445,6 @@ void MergeTreeReader::fillMissingColumns(Block & res, const Names & ordered_name
         bool should_evaluate_defaults = false;
         bool should_sort = always_reorder;
 
-        size_t rows = res.rows();
-
         /// insert default values only for columns without default expressions
         for (const auto & requested_column : columns)
         {
@@ -497,7 +496,7 @@ void MergeTreeReader::fillMissingColumns(Block & res, const Names & ordered_name
         }
 
         /// evaluate defaulted columns if necessary
-        if (should_evaluate_defaults)
+        if (!never_evaluate_defaults && should_evaluate_defaults)
             evaluateMissingDefaults(res, columns, storage.getColumns().defaults, storage.context);
 
         /// sort columns to ensure consistent order among all blocks

dbms/src/Storages/MergeTree/MergeTreeReader.h

@@ -44,7 +44,11 @@ public:
     /// Add columns from ordered_names that are not present in the block.
     /// Missing columns are added in the order specified by ordered_names.
     /// If at least one column was added, reorders all columns in the block according to ordered_names.
-    void fillMissingColumns(Block & res, const Names & ordered_names, const bool always_reorder);
+    /// Rows is the number of rows will be used to create default columns. It's res.rows() when all columns in block has the same size.
+    /// This function may be used in order to create default columns in nested structures. In that case block may has
+    /// columns with different size, and default columns can't be evaluated, so never_evaluate_defaults = false is used.
+    void fillMissingColumns(Block & res, const Names & ordered_names, const bool always_reorder,
+                            size_t rows, bool never_evaluate_defaults = false);
 
 private:
     class Stream