Allow default expressions to be attached to columns of foreign tables.

There's still some discussion about exactly how postgres_fdw ought to
handle this case, but there seems no debate that we want to allow defaults
to be used for inserts into foreign tables.  So remove the core-code
restrictions that prevented it.

While at it, get rid of the special grammar productions for CREATE FOREIGN
TABLE, and instead add explicit FEATURE_NOT_SUPPORTED error checks for the
disallowed cases.  This makes the grammar a shade smaller, and more
importantly results in much more intelligible error messages for
unsupported cases.  It's also one less thing to fix if we ever start
supporting constraints on foreign tables.

2 files changed, 13 insertions, 15 deletions

diff --git a/src/test/regress/expected/foreign_data.out b/src/test/regress/expected/foreign_data.out
index 1bfdca134bb..60506e07b1c 100644
--- a/src/test/regress/expected/foreign_data.out
+++ b/src/test/regress/expected/foreign_data.out
@@ -664,8 +664,6 @@ LINE 1: CREATE FOREIGN TABLE ft1 ();
                                    ^
 CREATE FOREIGN TABLE ft1 () SERVER no_server;                   -- ERROR
 ERROR:  server "no_server" does not exist
-CREATE FOREIGN TABLE ft1 (c1 serial) SERVER sc;                 -- ERROR
-ERROR:  default values on foreign tables are not supported
 CREATE FOREIGN TABLE ft1 () SERVER s0 WITH OIDS;                -- ERROR
 ERROR:  syntax error at or near "WITH OIDS"
 LINE 1: CREATE FOREIGN TABLE ft1 () SERVER s0 WITH OIDS;
@@ -707,17 +705,14 @@ COMMENT ON FOREIGN TABLE ft1 IS NULL;
 COMMENT ON COLUMN ft1.c1 IS 'foreign column';
 COMMENT ON COLUMN ft1.c1 IS NULL;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c4 integer;
-ALTER FOREIGN TABLE ft1 ADD COLUMN c5 integer DEFAULT 0;        -- ERROR
-ERROR:  default values on foreign tables are not supported
+ALTER FOREIGN TABLE ft1 ADD COLUMN c5 integer DEFAULT 0;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c6 integer;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c7 integer NOT NULL;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c8 integer;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c9 integer;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c10 integer OPTIONS (p1 'v1');
-ALTER FOREIGN TABLE ft1 ALTER COLUMN c4 SET DEFAULT 0;          -- ERROR
-ERROR:  "ft1" is not a table or view
-ALTER FOREIGN TABLE ft1 ALTER COLUMN c5 DROP DEFAULT;           -- ERROR
-ERROR:  "ft1" is not a table or view
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c4 SET DEFAULT 0;
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c5 DROP DEFAULT;
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c6 SET NOT NULL;
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c7 DROP NOT NULL;
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10) USING '0'; -- ERROR
@@ -739,7 +734,8 @@ ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 SET STATISTICS -1;
  c1     | integer | not null  | ("param 1" 'val1')             | plain    | 10000        | 
  c2     | text    |           | (param2 'val2', param3 'val3') | extended |              | 
  c3     | date    |           |                                | plain    |              | 
- c4     | integer |           |                                | plain    |              | 
+ c4     | integer | default 0 |                                | plain    |              | 
+ c5     | integer |           |                                | plain    |              | 
  c6     | integer | not null  |                                | plain    |              | 
  c7     | integer |           | (p1 'v1', p2 'v2')             | plain    |              | 
  c8     | text    |           | (p2 'V2')                      | extended |              | 
@@ -755,7 +751,9 @@ ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 SET DATA TYPE integer;	-- ERROR
 ERROR:  cannot alter foreign table "ft1" because column "use_ft1_column_type.x" uses its row type
 DROP TABLE use_ft1_column_type;
 ALTER FOREIGN TABLE ft1 ADD CONSTRAINT ft1_c9_check CHECK (c9 < 0); -- ERROR
-ERROR:  "ft1" is not a table
+ERROR:  constraints are not supported on foreign tables
+LINE 1: ALTER FOREIGN TABLE ft1 ADD CONSTRAINT ft1_c9_check CHECK (c...
+                                    ^
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT no_const;               -- ERROR
 ERROR:  "ft1" is not a table
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT IF EXISTS no_const;
@@ -783,7 +781,8 @@ ALTER FOREIGN TABLE foreign_schema.ft1 RENAME TO foreign_table_1;
  foreign_column_1 | integer | not null  | ("param 1" 'val1')
  c2               | text    |           | (param2 'val2', param3 'val3')
  c3               | date    |           | 
- c4               | integer |           | 
+ c4               | integer | default 0 | 
+ c5               | integer |           | 
  c6               | integer | not null  | 
  c7               | integer |           | (p1 'v1', p2 'v2')
  c8               | text    |           | (p2 'V2')
diff --git a/src/test/regress/sql/foreign_data.sql b/src/test/regress/sql/foreign_data.sql
index 38057db7b44..f819eb1b8eb 100644
--- a/src/test/regress/sql/foreign_data.sql
+++ b/src/test/regress/sql/foreign_data.sql
@@ -267,7 +267,6 @@ CREATE SCHEMA foreign_schema;
 CREATE SERVER s0 FOREIGN DATA WRAPPER dummy;
 CREATE FOREIGN TABLE ft1 ();                                    -- ERROR
 CREATE FOREIGN TABLE ft1 () SERVER no_server;                   -- ERROR
-CREATE FOREIGN TABLE ft1 (c1 serial) SERVER sc;                 -- ERROR
 CREATE FOREIGN TABLE ft1 () SERVER s0 WITH OIDS;                -- ERROR
 CREATE FOREIGN TABLE ft1 (
 	c1 integer OPTIONS ("param 1" 'val1') NOT NULL,
@@ -289,15 +288,15 @@ COMMENT ON COLUMN ft1.c1 IS 'foreign column';
 COMMENT ON COLUMN ft1.c1 IS NULL;
 
 ALTER FOREIGN TABLE ft1 ADD COLUMN c4 integer;
-ALTER FOREIGN TABLE ft1 ADD COLUMN c5 integer DEFAULT 0;        -- ERROR
+ALTER FOREIGN TABLE ft1 ADD COLUMN c5 integer DEFAULT 0;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c6 integer;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c7 integer NOT NULL;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c8 integer;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c9 integer;
 ALTER FOREIGN TABLE ft1 ADD COLUMN c10 integer OPTIONS (p1 'v1');
 
-ALTER FOREIGN TABLE ft1 ALTER COLUMN c4 SET DEFAULT 0;          -- ERROR
-ALTER FOREIGN TABLE ft1 ALTER COLUMN c5 DROP DEFAULT;           -- ERROR
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c4 SET DEFAULT 0;
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c5 DROP DEFAULT;
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c6 SET NOT NULL;
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c7 DROP NOT NULL;
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10) USING '0'; -- ERROR