Re: I want to make an example of using parameterized path - Mailing list pgsql-general

Thank you Jeff

I tried on PostgreSQL 9.1.0, and found the running result is:

postgres=# explain execute s(2);

                                   QUERY PLAN                                  

--------------------------------------------------------------------------------

-

 Bitmap Heap Scan on tst01 t  (cost=626.59..1486.25 rows=33333 width=4)

   Recheck Cond: (id < $1)

   ->  Bitmap Index Scan on idx_tst01_id  (cost=0.00..618.26 rows=33333 width=0)

         Index Cond: (id < $1)

(4 rows)

postgres=# explain execute s(10000);

                                   QUERY PLAN                                  

--------------------------------------------------------------------------------

-

 Bitmap Heap Scan on tst01 t  (cost=626.59..1486.25 rows=33333 width=4)

   Recheck Cond: (id < $1)

   ->  Bitmap Index Scan on idx_tst01_id  (cost=0.00..618.26 rows=33333 width=0)

         Index Cond: (id < $1)

(4 rows)

postgres=#

I want to know some internal about the "parameterized path".

I guess that  Before PG9.2,

     After I called  prepare command, the path and plan is already created and done.

     The plan is based on average estimation of all kinds of paths.

      So even when I put different parameter, it just  execute the same finished plan.