I would like to confirm my understand about memory allocation for varchar. I extracted the text below from MemSQL documentation, and my doubt is, If I put a bigger length for a varchar column (row store), MemSQL in memory will allocate the extra space or just the real length?
Variable-Length Strings
There are several variable-length string types. The data for these variable types are stored in a memory allocation designed for them, and pointers to their locations in memory are stored in the main table structure. This means that the space consumed by a particular value is the byte length of the string, plus an 8-byte overhead for the pointer, and a 4-byte overhead for storing the length. (There is an additional 4-byte overhead if the field is nullable.) One exception is values less than 7 bytes long. Those small values are stored directly in the pointer area.