• Go to backend>main and open main.c. Scroll down and you will find a call to PostgresMain, which is the actual main function for the backend
• Use open declaration on Eclipse to open the file containing PostgresMain() (this is in postgres.c)
• Scroll down and you will find that simple queries are executed by calling exec_simple_query(). Open the declaration of that function. (This is also in postgres.c)
• You can see what are the key steps in processing a simple query in this function. You can set breakpoints at pg_analyze_and_rewrite and at pg_plan_queries to see how a query is planned. A "portal" is a ready-to-execute statement, and PortalRun executes the statement. Here's a partial call sequence for executing a select query.
  1. ExecutorRun
  2. ExecutePlan
  3. ExecProcNode (this is a function pointer in plan, which is used to call the appropriate function depending on the operator type; execProcnode.c has more details). <\ol> See the header notes in execProcnode.c for a more detailed example of the execution sequence.
  4. Here are some files that help understand what is happening:
     • Access methods: Look at header comments of access/heap/heapam.c, access/index/indexam.c, and access/nbtree/nbtree.c