Replace pg_attribute.attisinherited with attislocal and attinhcount

columns, to allow more correct behavior in multiple-inheritance cases.
Patch by Alvaro Herrera, review by Tom Lane.

src/test/regress/expected/alter_table.out

@@ -1054,3 +1054,116 @@ alter table renameColumn add column w int;
 -- this should fail
 alter table only renameColumn add column x int;
 ERROR:  Attribute must be added to child tables too
+-- Test corner cases in dropping of inherited columns
+create table p1 (f1 int, f2 int);
+create table c1 (f1 int not null) inherits(p1);
+NOTICE:  CREATE TABLE: merging attribute "f1" with inherited definition
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+ERROR:  ALTER TABLE: Cannot drop inherited column "f1"
+-- should work
+alter table p1 drop column f1;
+-- c1.f1 is still there, but no longer inherited
+select f1 from c1;
+ f1 
+----
+(0 rows)
+
+alter table c1 drop column f1;
+select f1 from c1;
+ERROR:  Attribute "f1" not found
+drop table p1 cascade;
+NOTICE:  Drop cascades to table c1
+create table p1 (f1 int, f2 int);
+create table c1 () inherits(p1);
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+ERROR:  ALTER TABLE: Cannot drop inherited column "f1"
+alter table p1 drop column f1;
+-- c1.f1 is dropped now, since there is no local definition for it
+select f1 from c1;
+ERROR:  Attribute "f1" not found
+drop table p1 cascade;
+NOTICE:  Drop cascades to table c1
+create table p1 (f1 int, f2 int);
+create table c1 () inherits(p1);
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+ERROR:  ALTER TABLE: Cannot drop inherited column "f1"
+alter table only p1 drop column f1;
+-- c1.f1 is NOT dropped, but must now be considered non-inherited
+alter table c1 drop column f1;
+drop table p1 cascade;
+NOTICE:  Drop cascades to table c1
+create table p1 (f1 int, f2 int);
+create table c1 (f1 int not null) inherits(p1);
+NOTICE:  CREATE TABLE: merging attribute "f1" with inherited definition
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+ERROR:  ALTER TABLE: Cannot drop inherited column "f1"
+alter table only p1 drop column f1;
+-- c1.f1 is still there, but no longer inherited
+alter table c1 drop column f1;
+drop table p1 cascade;
+NOTICE:  Drop cascades to table c1
+create table p1(id int, name text);
+create table p2(id2 int, name text, height int);
+create table c1(age int) inherits(p1,p2);
+NOTICE:  CREATE TABLE: merging multiple inherited definitions of attribute "name"
+create table gc1() inherits (c1);
+select relname, attname, attinhcount, attislocal
+from pg_class join pg_attribute on (pg_class.oid = pg_attribute.attrelid)
+where relname in ('p1','p2','c1','gc1') and attnum > 0 and not attisdropped
+order by relname, attnum;
+ relname | attname | attinhcount | attislocal 
+---------+---------+-------------+------------
+ c1      | id      |           1 | f
+ c1      | name    |           2 | f
+ c1      | id2     |           1 | f
+ c1      | height  |           1 | f
+ c1      | age     |           0 | t
+ gc1     | id      |           1 | f
+ gc1     | name    |           1 | f
+ gc1     | id2     |           1 | f
+ gc1     | height  |           1 | f
+ gc1     | age     |           1 | f
+ p1      | id      |           0 | t
+ p1      | name    |           0 | t
+ p2      | id2     |           0 | t
+ p2      | name    |           0 | t
+ p2      | height  |           0 | t
+(15 rows)
+
+-- should work
+alter table only p1 drop column name;
+-- should work. Now c1.name is local and inhcount is 0.
+alter table p2 drop column name;
+-- should be rejected since its inherited
+alter table gc1 drop column name;
+ERROR:  ALTER TABLE: Cannot drop inherited column "name"
+-- should work, and drop gc1.name along
+alter table c1 drop column name;
+-- should fail: column does not exist
+alter table gc1 drop column name;
+ERROR:  Relation "gc1" has no column "name"
+-- should work and drop the attribute in all tables
+alter table p2 drop column height;
+select relname, attname, attinhcount, attislocal
+from pg_class join pg_attribute on (pg_class.oid = pg_attribute.attrelid)
+where relname in ('p1','p2','c1','gc1') and attnum > 0 and not attisdropped
+order by relname, attnum;
+ relname | attname | attinhcount | attislocal 
+---------+---------+-------------+------------
+ c1      | id      |           1 | f
+ c1      | id2     |           1 | f
+ c1      | age     |           0 | t
+ gc1     | id      |           1 | f
+ gc1     | id2     |           1 | f
+ gc1     | age     |           1 | f
+ p1      | id      |           0 | t
+ p2      | id2     |           0 | t
+(8 rows)
+
+drop table p1, p2 cascade;
+NOTICE:  Drop cascades to table c1
+NOTICE:  Drop cascades to table gc1

src/test/regress/expected/type_sanity.out

@@ -170,7 +170,8 @@ WHERE (p1.relkind = 'i' AND p1.relam = 0) OR
 SELECT p1.attrelid, p1.attname
 FROM pg_attribute as p1
 WHERE p1.attrelid = 0 OR p1.atttypid = 0 OR p1.attnum = 0 OR
-    p1.attcacheoff != -1;
+    p1.attcacheoff != -1 OR p1.attinhcount < 0 OR
+    (p1.attinhcount = 0 AND NOT p1.attislocal);
  attrelid | attname 
 ----------+---------
 (0 rows)

src/test/regress/sql/alter_table.sql

@@ -764,3 +764,83 @@ alter table renameColumn add column w int;
 
 -- this should fail
 alter table only renameColumn add column x int;
+
+
+-- Test corner cases in dropping of inherited columns
+
+create table p1 (f1 int, f2 int);
+create table c1 (f1 int not null) inherits(p1);
+
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+-- should work
+alter table p1 drop column f1;
+-- c1.f1 is still there, but no longer inherited
+select f1 from c1;
+alter table c1 drop column f1;
+select f1 from c1;
+
+drop table p1 cascade;
+
+create table p1 (f1 int, f2 int);
+create table c1 () inherits(p1);
+
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+alter table p1 drop column f1;
+-- c1.f1 is dropped now, since there is no local definition for it
+select f1 from c1;
+
+drop table p1 cascade;
+
+create table p1 (f1 int, f2 int);
+create table c1 () inherits(p1);
+
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+alter table only p1 drop column f1;
+-- c1.f1 is NOT dropped, but must now be considered non-inherited
+alter table c1 drop column f1;
+
+drop table p1 cascade;
+
+create table p1 (f1 int, f2 int);
+create table c1 (f1 int not null) inherits(p1);
+
+-- should be rejected since c1.f1 is inherited
+alter table c1 drop column f1;
+alter table only p1 drop column f1;
+-- c1.f1 is still there, but no longer inherited
+alter table c1 drop column f1;
+
+drop table p1 cascade;
+
+create table p1(id int, name text);
+create table p2(id2 int, name text, height int);
+create table c1(age int) inherits(p1,p2);
+create table gc1() inherits (c1);
+
+select relname, attname, attinhcount, attislocal
+from pg_class join pg_attribute on (pg_class.oid = pg_attribute.attrelid)
+where relname in ('p1','p2','c1','gc1') and attnum > 0 and not attisdropped
+order by relname, attnum;
+
+-- should work
+alter table only p1 drop column name;
+-- should work. Now c1.name is local and inhcount is 0.
+alter table p2 drop column name;
+-- should be rejected since its inherited
+alter table gc1 drop column name;
+-- should work, and drop gc1.name along
+alter table c1 drop column name;
+-- should fail: column does not exist
+alter table gc1 drop column name;
+-- should work and drop the attribute in all tables
+alter table p2 drop column height;
+
+select relname, attname, attinhcount, attislocal
+from pg_class join pg_attribute on (pg_class.oid = pg_attribute.attrelid)
+where relname in ('p1','p2','c1','gc1') and attnum > 0 and not attisdropped
+order by relname, attnum;
+
+drop table p1, p2 cascade;

src/test/regress/sql/type_sanity.sql

@@ -137,7 +137,8 @@ WHERE (p1.relkind = 'i' AND p1.relam = 0) OR
 SELECT p1.attrelid, p1.attname
 FROM pg_attribute as p1
 WHERE p1.attrelid = 0 OR p1.atttypid = 0 OR p1.attnum = 0 OR
-    p1.attcacheoff != -1;
+    p1.attcacheoff != -1 OR p1.attinhcount < 0 OR
+    (p1.attinhcount = 0 AND NOT p1.attislocal);
 
 -- Cross-check attnum against parent relation