Once in a compressed QDB, how is the data decompressed?
When queries are made against the database, data is searched while remaining in its compressed form. The data gets decompressed only when it is returned as the result of a query. A shared library sits with the table that tells the query engine how to decompress it. • Can compressed QD data be browsed? Yes, a user can browse the data in a compressed database. Browsing only decompresses the parts of the data that are actively being reviewed. Any tool that supports SQL can be used to browse the data. • What are the variables that determine the compression ratio (QD vs. native RDBMS) other than the elimination of white space? The amount of compression that QD is able to achieve is based on the data content of each column in the database. Specifically, the actual data type, the range of values, and the number of unique values will determine the compression technique QD will use, especially for numeric and date fields. For non-numeric fields, the structure and cardinality of the column will
