parallel safe/unsafe functions

gistfile1.txt

testdb=# select version();
                                                   version
-------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.6beta2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-17), 64-bit
(1 row)

testdb=# create table t1 as
testdb-# select generate_series(1,10000000) c1;
SELECT 10000000
testdb=# set force_parallel_mode = true;
SET
testdb=# set max_parallel_workers_per_gather = 4;
SET
testdb=# create or replace function f1_safe(c int8)
testdb-#   returns int8
testdb-# as
testdb-# $$
testdb$# begin
testdb$#   return c;
testdb$# end
testdb$# $$
testdb-# parallel safe
testdb-# language 'plpgsql';
CREATE FUNCTION
testdb=# create or replace function f1_unsafe(c int8)
testdb-#   returns int8
testdb-# as
testdb-# $$
testdb$# begin
testdb$#   return c;
testdb$# end
testdb$# $$
testdb-# parallel unsafe
testdb-# language 'plpgsql';
CREATE FUNCTION
testdb=# create or replace function f1_safe_unsafe(c int8)
testdb-#   returns int8
testdb-# as
testdb-# $$
testdb$# begin
testdb$#   return f1_unsafe(c);
testdb$# end
testdb$# $$
testdb-# parallel safe
testdb-# language 'plpgsql';
CREATE FUNCTION
testdb=# create or replace function f1_unsafe_unsafe(c int8)
testdb-#   returns int8
testdb-# as
testdb-# $$
testdb$# begin
testdb$#   return f1_unsafe(c);
testdb$# end
testdb$# $$
testdb-# parallel unsafe
testdb-# language 'plpgsql';
CREATE FUNCTION
testdb=# explain verbose select f1_safe(c1) from t1;
                                 QUERY PLAN
----------------------------------------------------------------------------
 Gather  (cost=0.00..0.00 rows=0 width=0)
   Output: (f1_safe((c1)::bigint))
   Workers Planned: 1
   Single Copy: true
   ->  Seq Scan on public.t1  (cost=0.00..3006098.50 rows=11283240 width=8)
         Output: f1_safe((c1)::bigint)
(6 rows)

testdb=# explain verbose select f1_unsafe(c1) from t1;
                              QUERY PLAN
----------------------------------------------------------------------
 Seq Scan on public.t1  (cost=0.00..3006098.50 rows=11283240 width=8)
   Output: f1_unsafe((c1)::bigint)
(2 rows)

testdb=# explain verbose select f1_safe_unsafe(c1) from t1;
                                 QUERY PLAN
----------------------------------------------------------------------------
 Gather  (cost=0.00..0.00 rows=0 width=0)
   Output: (f1_safe_unsafe((c1)::bigint))
   Workers Planned: 1
   Single Copy: true
   ->  Seq Scan on public.t1  (cost=0.00..3006098.50 rows=11283240 width=8)
         Output: f1_safe_unsafe((c1)::bigint)
(6 rows)

testdb=# explain verbose select f1_unsafe_unsafe(c1) from t1;
                              QUERY PLAN
----------------------------------------------------------------------
 Seq Scan on public.t1  (cost=0.00..3006098.50 rows=11283240 width=8)
   Output: f1_unsafe_unsafe((c1)::bigint)
(2 rows)

testdb=#