Add tests

src/test/regress/expected/multi_alias.out

@@ -168,9 +168,100 @@ DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
  6 | 7 | 8 |
 (3 rows)
 
+RESET citus.log_remote_commands;
+-- test everything on https://github.com/citusdata/citus/issues/7684
+CREATE TABLE test_name_prefix (
+attribute1 varchar(255),
+attribute2 varchar(255),
+attribute3 varchar(255)
+);
+INSERT INTO test_name_prefix (attribute1, attribute2, attribute3)
+VALUES ('Phone', 'John', 'A'),
+('Phone', 'Eric', 'A'),
+('Tablet','Eric', 'B');
+-- vanilla Postgres result
+-- with DISTINCT ON (T.attribute1, T.attribute2)
+-- we have 3 distinct groups of 1 row each
+-- (Phone, John) (Phone, Eric) and (Tablet, Eric)
+SELECT DISTINCT ON (T.attribute1, T.attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2,
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, T.attribute2;
+ attribute1 | attribute2 | attribute3
+---------------------------------------------------------------------
+ Phone      | A          | Eric
+ Phone      | A          | John
+ Tablet     | B          | Eric
+(3 rows)
+
+-- vanilla Postgres result
+-- changes when we remove the table-name prefix to attribute2
+-- in this case it uses the output column name,
+-- which is actually T.attribute3 (AS attribute2)
+-- so, with DISTINCT ON (T.attribute1, T.attribute3)
+-- we have only 2 distinct groups
+-- (Phone, A) and (Tablet, B)
+SELECT DISTINCT ON (T.attribute1, attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2, -- name match in output column name
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, attribute2;
+ attribute1 | attribute2 | attribute3
+---------------------------------------------------------------------
+ Phone      | A          | John
+ Tablet     | B          | Eric
+(2 rows)
+
+-- now, let's verify the distributed query scenario
+SELECT create_distributed_table('test_name_prefix', 'attribute1');
+NOTICE:  Copying data from local table...
+NOTICE:  copying the data has completed
+DETAIL:  The local data in the table is no longer visible, but is still on disk.
+HINT:  To remove the local data, run: SELECT truncate_local_data_after_distributing_table($$alias.test_name_prefix$$)
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+SET citus.log_remote_commands TO on;
+-- make sure we preserve the table-name prefix to attribute2
+-- when building the shard query
+-- (before this patch we wouldn't preserve T.attribute2)
+-- note that we only need to preserve T.attribute2, not T.attribute1
+-- because there is no confusion there
+SELECT DISTINCT ON (T.attribute1, T.attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2,
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, T.attribute2;
+NOTICE:  issuing SELECT DISTINCT ON (attribute1, t.attribute2) attribute1, attribute3 AS attribute2, attribute2 AS attribute3 FROM alias.test_name_prefix_90630803 t ORDER BY attribute1, t.attribute2
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+ attribute1 | attribute2 | attribute3
+---------------------------------------------------------------------
+ Phone      | A          | Eric
+ Phone      | A          | John
+ Tablet     | B          | Eric
+(3 rows)
+
+-- here Citus will replace attribute2 with T.attribute3
+SELECT DISTINCT ON (T.attribute1, attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2,
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, attribute2;
+NOTICE:  issuing SELECT DISTINCT ON (attribute1, t.attribute3) attribute1, attribute3 AS attribute2, attribute2 AS attribute3 FROM alias.test_name_prefix_90630803 t ORDER BY attribute1, t.attribute3
+DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
+ attribute1 | attribute2 | attribute3
+---------------------------------------------------------------------
+ Phone      | A          | John
+ Tablet     | B          | Eric
+(2 rows)
+
 RESET citus.log_remote_commands;
 DROP SCHEMA alias CASCADE;
-NOTICE:  drop cascades to 3 other objects
+NOTICE:  drop cascades to 4 other objects
 DETAIL:  drop cascades to table alias_test
 drop cascades to table test
 drop cascades to table test_2
+drop cascades to table test_name_prefix

src/test/regress/sql/multi_alias.sql

@@ -63,4 +63,65 @@ SELECT *
   ORDER BY a, d;
 
 RESET citus.log_remote_commands;
+
+-- test everything on https://github.com/citusdata/citus/issues/7684
+CREATE TABLE test_name_prefix (
+attribute1 varchar(255),
+attribute2 varchar(255),
+attribute3 varchar(255)
+);
+
+INSERT INTO test_name_prefix (attribute1, attribute2, attribute3)
+VALUES ('Phone', 'John', 'A'),
+('Phone', 'Eric', 'A'),
+('Tablet','Eric', 'B');
+
+-- vanilla Postgres result
+-- with DISTINCT ON (T.attribute1, T.attribute2)
+-- we have 3 distinct groups of 1 row each
+-- (Phone, John) (Phone, Eric) and (Tablet, Eric)
+SELECT DISTINCT ON (T.attribute1, T.attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2,
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, T.attribute2;
+
+-- vanilla Postgres result
+-- changes when we remove the table-name prefix to attribute2
+-- in this case it uses the output column name,
+-- which is actually T.attribute3 (AS attribute2)
+-- so, with DISTINCT ON (T.attribute1, T.attribute3)
+-- we have only 2 distinct groups
+-- (Phone, A) and (Tablet, B)
+SELECT DISTINCT ON (T.attribute1, attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2, -- name match in output column name
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, attribute2;
+
+-- now, let's verify the distributed query scenario
+SELECT create_distributed_table('test_name_prefix', 'attribute1');
+
+SET citus.log_remote_commands TO on;
+
+-- make sure we preserve the table-name prefix to attribute2
+-- when building the shard query
+-- (before this patch we wouldn't preserve T.attribute2)
+-- note that we only need to preserve T.attribute2, not T.attribute1
+-- because there is no confusion there
+SELECT DISTINCT ON (T.attribute1, T.attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2,
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, T.attribute2;
+
+-- here Citus will replace attribute2 with T.attribute3
+SELECT DISTINCT ON (T.attribute1, attribute2)
+T.attribute1 AS attribute1,
+T.attribute3 AS attribute2,
+T.attribute2 AS attribute3
+FROM test_name_prefix T ORDER BY T.attribute1, attribute2;
+
+RESET citus.log_remote_commands;
+
 DROP SCHEMA alias CASCADE;