Microsoft® SQL Server® 2012 Integration Services by Wee-Hyong Tok Rakesh Parida Matt Masson Xiaoning Ding & Kaarthik Sivashanmugam

Author:Wee-Hyong Tok, Rakesh Parida, Matt Masson, Xiaoning Ding & Kaarthik Sivashanmugam [Wee-Hyong Tok, Rakesh Parida, Matt Masson, Xiaoning Ding, and Kaarthik Sivashanmugam]
Language: eng
Format: epub
Tags: COMPUTERS / Database Management / General
ISBN: 9780735665835
Publisher: Microsoft Press
Published: 2012-08-28T16:00:00+00:00

Those subcontainer or tasks can be in parallel, in sequence, or both.

Those subcontainers or tasks could have their own event handlers.

It’s easy to realize that a sequence container has the exactly same scheduling requirements with an entire package, so the sequence container shares the same scheduling algorithm with a package object. It also maintains its own executable queues and calculates the precedence constraint.

Loop Containers After the sequence container is implemented, it’s easy to implement two loop containers. A loop container could be viewed as a special sequence container that will execute multiple times. The only extra cost is to evaluate the looping criteria. For example, a Foreach Loop container loads the corresponding loop enumerator. For each returned enumeration object, it will map the object to the corresponding variable and then execute the whole Control Flow in itself as a sequence container.

Event Handlers The last one is the implementation of the event handler. Because an event handler actually is a stand-alone Control Flow with access to some special system variables, its execution mechanism is also similar to the package execution mechanism. When an event is raised on a container, the container will check whether there is a corresponding event handler defined. If there is one, that event handler will be put into the ready queue as a new executable. The container continues to find matched event handlers upward until it hits the top-level container.