postgres_fdw: Allow partitions specified in LIMIT TO to be imported.

Commit f49bcd4ef3 disallowed postgres_fdw to import table partitions.
Because all data can be accessed through the partitioned table which
is the root of the partitioning hierarchy, importing only partitioned
table should allow access to all the data without creating extra objects.
This is a reasonable default when importing a whole schema. But there
may be the case where users want to explicitly import one of
a partitioned tables' partitions.

For that use case, this commit allows postgres_fdw to import tables or
foreign tables which are partitions of some other table only when they
are explicitly specified in LIMIT TO clause.  It doesn't change
the behavior that any partitions not specified in LIMIT TO are
automatically excluded in IMPORT FOREIGN SCHEMA command.

Author: Matthias van de Meent
Reviewed-by: Bernd Helmle, Amit Langote, Michael Paquier, Fujii Masao
Discussion: https://postgr.es/m/CAEze2Whwg4i=mzApMe+PXxCEfgoZmHGqdqQFW7J4bmj_5p6t1A@mail.gmail.com

1 files changed, 20 insertions, 16 deletions

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 59e4e27ffbe..9d472d2d3d6 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -8228,6 +8228,8 @@ ALTER TABLE import_source."x 5" DROP COLUMN c1;
 CREATE TABLE import_source.t4 (c1 int) PARTITION BY RANGE (c1);
 CREATE TABLE import_source.t4_part PARTITION OF import_source.t4
   FOR VALUES FROM (1) TO (100);
+CREATE TABLE import_source.t4_part2 PARTITION OF import_source.t4
+  FOR VALUES FROM (100) TO (200);
 CREATE SCHEMA import_dest1;
 IMPORT FOREIGN SCHEMA import_source FROM SERVER loopback INTO import_dest1;
 \det+ import_dest1.*
@@ -8419,27 +8421,29 @@ FDW options: (schema_name 'import_source', table_name 'x 5')
 
 -- Check LIMIT TO and EXCEPT
 CREATE SCHEMA import_dest4;
-IMPORT FOREIGN SCHEMA import_source LIMIT TO (t1, nonesuch)
+IMPORT FOREIGN SCHEMA import_source LIMIT TO (t1, nonesuch, t4_part)
   FROM SERVER loopback INTO import_dest4;
 \det+ import_dest4.*
-                                     List of foreign tables
-    Schema    | Table |  Server  |                  FDW options                   | Description 
---------------+-------+----------+------------------------------------------------+-------------
- import_dest4 | t1    | loopback | (schema_name 'import_source', table_name 't1') | 
-(1 row)
+                                        List of foreign tables
+    Schema    |  Table  |  Server  |                     FDW options                     | Description 
+--------------+---------+----------+-----------------------------------------------------+-------------
+ import_dest4 | t1      | loopback | (schema_name 'import_source', table_name 't1')      | 
+ import_dest4 | t4_part | loopback | (schema_name 'import_source', table_name 't4_part') | 
+(2 rows)
 
-IMPORT FOREIGN SCHEMA import_source EXCEPT (t1, "x 4", nonesuch)
+IMPORT FOREIGN SCHEMA import_source EXCEPT (t1, "x 4", nonesuch, t4_part)
   FROM SERVER loopback INTO import_dest4;
 \det+ import_dest4.*
-                                     List of foreign tables
-    Schema    | Table |  Server  |                   FDW options                   | Description 
---------------+-------+----------+-------------------------------------------------+-------------
- import_dest4 | t1    | loopback | (schema_name 'import_source', table_name 't1')  | 
- import_dest4 | t2    | loopback | (schema_name 'import_source', table_name 't2')  | 
- import_dest4 | t3    | loopback | (schema_name 'import_source', table_name 't3')  | 
- import_dest4 | t4    | loopback | (schema_name 'import_source', table_name 't4')  | 
- import_dest4 | x 5   | loopback | (schema_name 'import_source', table_name 'x 5') | 
-(5 rows)
+                                        List of foreign tables
+    Schema    |  Table  |  Server  |                     FDW options                     | Description 
+--------------+---------+----------+-----------------------------------------------------+-------------
+ import_dest4 | t1      | loopback | (schema_name 'import_source', table_name 't1')      | 
+ import_dest4 | t2      | loopback | (schema_name 'import_source', table_name 't2')      | 
+ import_dest4 | t3      | loopback | (schema_name 'import_source', table_name 't3')      | 
+ import_dest4 | t4      | loopback | (schema_name 'import_source', table_name 't4')      | 
+ import_dest4 | t4_part | loopback | (schema_name 'import_source', table_name 't4_part') | 
+ import_dest4 | x 5     | loopback | (schema_name 'import_source', table_name 'x 5')     | 
+(6 rows)
 
 -- Assorted error cases
 IMPORT FOREIGN SCHEMA import_source FROM SERVER loopback INTO import_dest4;