TIGER database evaluation plans

If we want to know what evaluation plan is being used by Postgres for a given query, we can ask. Specifically, we put the keyword EXPLAIN explain immediately before a query, and in this case it explains the query evaluation plan it will use if performing that query. (note that the actual query is not performed, thereby letting us see the plan even when a query is taking too long).

We will look at several examples taken from our last homework. Namely, we examine the different plans used for evaluating a possible query for questions A and E, when using any of the three distinct schemas.

Handouts:

• Question A
  • Textual output of EXPLAIN for each of the three schemas
  • Diagram of Evaluation Plan for tiger1 schemas
  • Diagram of Evaluation Plan for tiger2 schemas
  • Diagram of Evaluation Plan for tiger3 schemas
• Question E
  • Textual output of EXPLAIN for each of the three schemas
  • Diagram of Evaluation Plan for tiger1 schemas
  • Diagram of Evaluation Plan for tiger2 schemas
  • Diagram of Evaluation Plan for tiger3 schemas