Donot reserve memory for non-fixed type columns in decodeAndSquash (#…

…7418) (#7423)

close #7416

dbms/src/Flash/Coprocessor/CHBlockChunkCodec.cpp

@@ -16,6 +16,7 @@
 #include <DataStreams/IBlockInputStream.h>
 #include <DataStreams/NativeBlockInputStream.h>
 #include <DataTypes/DataTypeFactory.h>
+#include <DataTypes/DataTypeNullable.h>
 #include <Flash/Coprocessor/CHBlockChunkCodec.h>
 #include <Flash/Coprocessor/DAGUtils.h>
 #include <IO/ReadBufferFromString.h>
@@ -163,10 +164,14 @@ Block CHBlockChunkCodec::decodeImpl(ReadBuffer & istr, size_t reserve_size)
 
         /// Data
         MutableColumnPtr read_column = column.type->createColumn();
-        if (reserve_size > 0)
-            read_column->reserve(std::max(rows, reserve_size));
-        else if (rows)
-            read_column->reserve(rows);
+        const auto & type_removed_nullable = removeNullable(column.type);
+        if (type_removed_nullable->isValueRepresentedByNumber() || type_removed_nullable->isFixedString())
+        {
+            if (reserve_size > 0)
+                read_column->reserve(std::max(rows, reserve_size));
+            else if (rows)
+                read_column->reserve(rows);
+        }
 
         if (rows) /// If no rows, nothing to read.
             readData(*column.type, *read_column, istr, rows);