We usually adopt certain storage schemas that can increase performance and reduce space usage for physical table. But they lead to lower data readability and higher coding complexity. For example, using integers to represent enumerated values or using bits of integer field to store boolean values. Integers and binary digits are not as easy to read as strings and booleans. And we need to write code for type and base conversions over these physical values. In this case, pseudo tables are the problem solver.
Instead of a fact table, a pseudo table is a logical table defined on a physical table. We can define easier to use logical fields in a pseudo table. Such logical fields are called pseudo fields, and fields that physically exist in the physical table are called real fields.
Through mapping between the pseudo fields and the real fields, a pseudo table encapsulates the special storage structure and achieves storage transparency for the physical table. This helps reduce hard disk usage and increase performance, as well as making data easier to read and handle.
For users who do not so familiar with SPL, it’s a little difficult to define a pseudo table in esProc. Metadata Editor’s defining pseudo table’s feature makes it convenient to define a pseudo table before they learn to use SPL well.
In A quick guide: Step2: Define a pseudo table, we explained how to quickly define a pseudo table based on a composite table. Following we’ll illustrate the processing of defining complex pseudo tables using Metadata Editor and applications of defined pseudo tables.