The primary index is the system for doling out an information column to an AMP and an area on the AMP's plates. Files additionally used to access lines from a table without looking through the whole table. Secondary indexes upgrade set determination by indicating access ways less every now and again utilized than the essential file way. Optional lists are likewise used to encourage total activities.
If a secondary index covers a query, at that point the Optimizer verifies that it would be less exorbitant to gets to its columns legitimately as opposed to utilizing it to get to the base table lines it focuses to. Some of the time, different optional lists with low individual selectivity can be covered and bit-mapped to give upgraded work process.