2.14.1 Variable-length Encoding

2.14.1.1 VARLEN Supported Expressions, Filters, Functions, and Operators

2.14.1.2 VARLEN Encoding Limits

2.14.1.3 VARLEN Column Memory Requirements

2.14.1.4 VARLEN Encoding and Performance

Variable-length (VARLEN) encoding has the following characteristics:

• It is the default encoding type. No action is required to use variable-length encoding. It is applied to string columns by default when tables are loaded with the exception of string columns defined explicitly as dictionary-encoded columns.

• It minimizes the amount of data stored for string columns by efficiently storing variable length column values.

• It is more efficient than dictionary encoding with respect to storage and processing of string columns with a high number of distinct values relative to the cardinality of the table.

• It permits more operations involving string columns to be offloaded than dictionary encoding.

• It supports all character sets and collation types supported by the MySQL DB System. User defined character sets are not supported.

• VARLEN columns can be declared as NULL.