Parsing Engine

A Parsing Engine (PE) is a virtual processor (vproc) and can supports maximum 120 sessions It is made up of the following software components:

• Session Control
• Parser
• Optimizer
• Dispatcher

 

The Session Control component verifies the request for session authorization (user names and passwords), and either allows or disallows the request.

The Parser does the following.

• The PE checks the user's SQL Syntax.
• The PE checks the user‘s security rights.
• The PE comes up with a plan for the AMPs to follow.
• The PE passes the plan along to the AMPs over the BYNET.
• The AMPs follow the plan and retrieve the data requested.
• The AMPs pass the data to the PE over the BYNET.
• The PE then passes the final data to the user.

The Optimizer is cost-based and develops the least expensive plan (in terms of time) to return the requested response set.The optimizer must know about system configuration, available units of parallelism (AMPs and PE's), and data demographics. The Teradata Optimizer is robust and intelligent. The optimizer enables Teradata to handle multiple complex, ad hoc queries efficiently. It is parallel-aware and cost-based and uses full look-ahead capability. 

The Dispatcher controls the sequence in which the steps are executed and passes the steps received from the optimizer onto the BYNET for execution by the AMPs. After the AMPs process the steps, the PE receives their responses over the BYNET.