Basic partition-wise join functionality.

Instead of joining two partitioned tables in their entirety we can, if
it is an equi-join on the partition keys, join the matching partitions
individually.  This involves teaching the planner about "other join"
rels, which are related to regular join rels in the same way that
other member rels are related to baserels.  This can use significantly
more CPU time and memory than regular join planning, because there may
now be a set of "other" rels not only for every base relation but also
for every join relation.  In most practical cases, this probably
shouldn't be a problem, because (1) it's probably unusual to join many
tables each with many partitions using the partition keys for all
joins and (2) if you do that scenario then you probably have a big
enough machine to handle the increased memory cost of planning and (3)
the resulting plan is highly likely to be better, so what you spend in
planning you'll make up on the execution side.  All the same, for now,
turn this feature off by default.

Currently, we can only perform joins between two tables whose
partitioning schemes are absolutely identical.  It would be nice to
cope with other scenarios, such as extra partitions on one side or the
other with no match on the other side, but that will have to wait for
a future patch.

Ashutosh Bapat, reviewed and tested by Rajkumar Raghuwanshi, Amit
Langote, Rafia Sabih, Thomas Munro, Dilip Kumar, Antonin Houska, Amit
Khandekar, and by me.  A few final adjustments by me.

Discussion: http://postgr.es/m/CAFjFpRfQ8GrQvzp3jA2wnLqrHmaXna-urjm_UY9BqXj=EaDTSA@mail.gmail.com
Discussion: http://postgr.es/m/CAFjFpRcitjfrULr5jfuKWRPsGUX0LQ0k8-yG0Qw2+1LBGNpMdw@mail.gmail.com

1 files changed, 53 insertions, 0 deletions

diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 5f65d9d966c..ddfec7930d5 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -1764,3 +1764,56 @@ WHERE ftrelid = 'table30000'::regclass
 AND ftoptions @> array['fetch_size=60000'];
 
 ROLLBACK;
+
+-- ===================================================================
+-- test partition-wise-joins
+-- ===================================================================
+SET enable_partition_wise_join=on;
+
+CREATE TABLE fprt1 (a int, b int, c varchar) PARTITION BY RANGE(a);
+CREATE TABLE fprt1_p1 (LIKE fprt1);
+CREATE TABLE fprt1_p2 (LIKE fprt1);
+INSERT INTO fprt1_p1 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(0, 249, 2) i;
+INSERT INTO fprt1_p2 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(250, 499, 2) i;
+CREATE FOREIGN TABLE ftprt1_p1 PARTITION OF fprt1 FOR VALUES FROM (0) TO (250)
+	SERVER loopback OPTIONS (table_name 'fprt1_p1', use_remote_estimate 'true');
+CREATE FOREIGN TABLE ftprt1_p2 PARTITION OF fprt1 FOR VALUES FROM (250) TO (500)
+	SERVER loopback OPTIONS (TABLE_NAME 'fprt1_p2');
+ANALYZE fprt1;
+ANALYZE fprt1_p1;
+ANALYZE fprt1_p2;
+
+CREATE TABLE fprt2 (a int, b int, c varchar) PARTITION BY RANGE(b);
+CREATE TABLE fprt2_p1 (LIKE fprt2);
+CREATE TABLE fprt2_p2 (LIKE fprt2);
+INSERT INTO fprt2_p1 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(0, 249, 3) i;
+INSERT INTO fprt2_p2 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(250, 499, 3) i;
+CREATE FOREIGN TABLE ftprt2_p1 PARTITION OF fprt2 FOR VALUES FROM (0) TO (250)
+	SERVER loopback OPTIONS (table_name 'fprt2_p1', use_remote_estimate 'true');
+CREATE FOREIGN TABLE ftprt2_p2 PARTITION OF fprt2 FOR VALUES FROM (250) TO (500)
+	SERVER loopback OPTIONS (table_name 'fprt2_p2', use_remote_estimate 'true');
+ANALYZE fprt2;
+ANALYZE fprt2_p1;
+ANALYZE fprt2_p2;
+
+-- inner join three tables
+EXPLAIN (COSTS OFF)
+SELECT t1.a,t2.b,t3.c FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) INNER JOIN fprt1 t3 ON (t2.b = t3.a) WHERE t1.a % 25 =0 ORDER BY 1,2,3;
+SELECT t1.a,t2.b,t3.c FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) INNER JOIN fprt1 t3 ON (t2.b = t3.a) WHERE t1.a % 25 =0 ORDER BY 1,2,3;
+
+-- left outer join + nullable clasue
+EXPLAIN (COSTS OFF)
+SELECT t1.a,t2.b,t2.c FROM fprt1 t1 LEFT JOIN (SELECT * FROM fprt2 WHERE a < 10) t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a < 10 ORDER BY 1,2,3;
+SELECT t1.a,t2.b,t2.c FROM fprt1 t1 LEFT JOIN (SELECT * FROM fprt2 WHERE a < 10) t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a < 10 ORDER BY 1,2,3;
+
+-- with whole-row reference
+EXPLAIN (COSTS OFF)
+SELECT t1,t2 FROM fprt1 t1 JOIN fprt2 t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a % 25 =0 ORDER BY 1,2;
+SELECT t1,t2 FROM fprt1 t1 JOIN fprt2 t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a % 25 =0 ORDER BY 1,2;
+
+-- join with lateral reference
+EXPLAIN (COSTS OFF)
+SELECT t1.a,t1.b FROM fprt1 t1, LATERAL (SELECT t2.a, t2.b FROM fprt2 t2 WHERE t1.a = t2.b AND t1.b = t2.a) q WHERE t1.a%25 = 0 ORDER BY 1,2;
+SELECT t1.a,t1.b FROM fprt1 t1, LATERAL (SELECT t2.a, t2.b FROM fprt2 t2 WHERE t1.a = t2.b AND t1.b = t2.a) q WHERE t1.a%25 = 0 ORDER BY 1,2;
+
+RESET enable_partition_wise_join;