pg_stat_plans_explain can cause unexpected query invocation on multistatement query strings

[terrorobe]

Example:

foo=# select * from pg_stat_plans where planid = 4291451842;
-[ RECORD 1 ]-------+-------------------------------------------------------------------
planid              | 4291451842
userid              | 16384
dbid                | 126346
query               | insert into test(foo) values(7); insert into test(foo) values(11);
had_our_search_path | t
from_our_database   | t
query_explainable   | t
calls               | 12
total_time          | 0.532
rows                | 12
shared_blks_hit     | 65
shared_blks_read    | 1
shared_blks_written | 0
local_blks_hit      | 0
local_blks_read     | 0
local_blks_written  | 0
temp_blks_read      | 0
temp_blks_written   | 0
blk_read_time       | 0
blk_write_time      | 0
last_startup_cost   | 0
last_total_cost     | 0.015

foo=# truncate table test;
TRUNCATE TABLE
foo=# select * from test;
(No rows)
foo=# select pg_stat_plans_explain(4291451842, 16384, 126346);
-[ RECORD 1 ]---------+-------------------------------------------------
pg_stat_plans_explain | Insert on test  (cost=0.00..0.01 rows=1 width=0)
                      |   ->  Result  (cost=0.00..0.01 rows=1 width=0)

foo=# select * from test;
-[ RECORD 1 ]
id  | 82
foo | 11

To reproduce:

Generate a multi-statement entry in pg_stat_plans, e.g. with python/psycopg2. Doesn't seem to work from within psql.

#!/usr/bin/env python
import psycopg2

conn = psycopg2.connect("dbname='foo'")
curs = conn.cursor()

query = 'insert into test(foo) values(7); insert into test(foo) values(11);'
curs.execute(query)
conn.commit()

pg_stat_plans_explain will execute everything after the first semicolon/query literal.