What Is A Row Source Generator In Oracle | Interview Q&A

Here we are going to understand row source generator in oracle

What is a Row Source Generator?

• The Row Source Generator is the next step of the plan generator.
• Once the plan generator generates the optimum plan, it handles that into the row source generator.
• The plan generator decides how to join two tables, how to access the table or the index and what join methods to be applied.
• The row generator advances this plan and generates an iterative execution plan that is more usable for the database.
• It creates a step by step execution by row sources.
• A row source is an area where we get the row set. They might be a table, a view or the result of a join or a grouping operation, etc. So the row source generator produces a row source tree, which is a collection of row sources.
• In each step returns a row set and that row set were used by the next step.
• The row source tree shows in the execution order of the tables in the statement, the Access method of each table, join method, data operation like a filter, sort, aggregation, etc.
• It generates an iterative execution plan.
• In the below example, we can see the representation of the iterative execution plan.

Sample Query of Joins

Sample Execution Plan

• In each step are indented differently. These indents are representing which one is executed first, then the result is passed to the less indented one.
• It is the final representation of the execution plan.

Conclusion:

• Row source generators create an iterative execution plan. Step by step execution and the source of these executions.
• Our query is executed exactly in the same order with that plan.