Hi!
Just in case you'd like to include sleepsort as a test, here it is
wrapped as a regression test(see attachment). But it has serious
downside: it runs no less than 5 seconds.
Also I'll list here every parallelism feature I managed to imagine. It
is not to say that I suggest having some of these features at v1. We
certainly have to start somewhere, this list is just for information
purposes.
1. Poolable workers. Just to be sure you can reliably queue your task
somewhere without having "increase max_connections" hint.
2. Inside one pool, you can have task chaining. After competition of
task A (query A) start task B, in case of failure start task C. Task C
is followed by task D.
3. Reliably read task status: running\awaiting\completed\errored\in a
lock. Get a query plan of a task? (I know, there are reasons why it is
not possible now)
4. Query as a future (actually it is implemented already by
pg_background_result)
5. Promised result. Declare that you are waiting for data of specific
format, execute a query, someone (from another backend) will
eventually place a data to promised result and your query continues
execution.
6. Cancelation: a way to signal to background query that it's time to
quit gracefully.
Best regards, Andrey Borodin.
diff --git a/contrib/pg_background/Makefile b/contrib/pg_background/Makefile
index c4e717d..085fbff 100644
--- a/contrib/pg_background/Makefile
+++ b/contrib/pg_background/Makefile
@@ -6,6 +6,8 @@ OBJS = pg_background.o
EXTENSION = pg_background
DATA = pg_background--1.0.sql
+REGRESS = pg_background
+
ifdef USE_PGXS
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)
diff --git a/contrib/pg_background/expected/pg_background.out
b/contrib/pg_background/expected/pg_background.out
new file mode 100644
index 0000000..dbc344e
--- /dev/null
+++ b/contrib/pg_background/expected/pg_background.out
@@ -0,0 +1,26 @@
+CREATE EXTENSION pg_background;
+--run 5 workers which wait about 1 second
+CREATE TABLE input as SELECT x FROM generate_series(1,5,1) x ORDER BY x DESC;
+CREATE TABLE output(place int,value int);
+CREATE sequence s start 1;
+CREATE TABLE handles as SELECT pg_background_launch('select pg_sleep('||x||');
insert into output values (nextval(''s''),'||x||');') h FROM input;
+SELECT (SELECT * FROM pg_background_result(h) as (x text) limit 1) FROM
handles;
+ x
+----------
+ SELECT 1
+ SELECT 1
+ SELECT 1
+ SELECT 1
+ SELECT 1
+(5 rows)
+
+SELECT * FROM output ORDER BY place;
+ place | value
+-------+-------
+ 1 | 1
+ 2 | 2
+ 3 | 3
+ 4 | 4
+ 5 | 5
+(5 rows)
+
diff --git a/contrib/pg_background/sql/pg_background.sql
b/contrib/pg_background/sql/pg_background.sql
new file mode 100644
index 0000000..d7cbd44
--- /dev/null
+++ b/contrib/pg_background/sql/pg_background.sql
@@ -0,0 +1,9 @@
+CREATE EXTENSION pg_background;
+
+--run 5 workers which wait about 1 second
+CREATE TABLE input as SELECT x FROM generate_series(1,5,1) x ORDER BY x DESC;
+CREATE TABLE output(place int,value int);
+CREATE sequence s start 1;
+CREATE TABLE handles as SELECT pg_background_launch('select pg_sleep('||x||');
insert into output values (nextval(''s''),'||x||');') h FROM input;
+SELECT (SELECT * FROM pg_background_result(h) as (x text) limit 1) FROM
handles;
+SELECT * FROM output ORDER BY place;
--
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