cursor plans invalidation

test.sql

drop table if exists tst_stats;

create table tst_stats (
	id bigserial primary key,
	value text
);

insert into tst_stats (value)
select 'value ' || (i*i)
from generate_series(1, 100) g (i);

analyze tst_stats;

prepare q_stats as
select value from tst_stats where id < 90;

explain (analyze,buffers)
execute q_stats;

/*
QUERY PLAN                                                                                          |
----------------------------------------------------------------------------------------------------+
Seq Scan on tst_stats  (cost=0.00..2.25 rows=89 width=10) (actual time=0.009..0.017 rows=89 loops=1)|
  Filter: (id < 90)                                                                                 |
  Rows Removed by Filter: 11                                                                        |
  Buffers: shared hit=1                                                                             |
Planning Time: 0.002 ms                                                                             |
Execution Time: 0.038 ms                                                                            |
 */

insert into tst_stats (value)
select 'x value ' || i
from generate_series(1, 100*1000) g (i);

analyze tst_stats;

explain (analyze,buffers)
execute q_stats;

/*
QUERY PLAN                                                                                                                 |
---------------------------------------------------------------------------------------------------------------------------+
Index Scan using tst_stats_pkey on tst_stats  (cost=0.29..3.89 rows=80 width=13) (actual time=0.004..0.015 rows=89 loops=1)|
  Index Cond: (id < 90)                                                                                                    |
  Buffers: shared hit=3                                                                                                    |
Planning:                                                                                                                  |
  Buffers: shared hit=11                                                                                                   |
Planning Time: 0.111 ms                                                                                                    |
Execution Time: 0.029 ms                                                                                                   |
 */

deallocate q_stats;