Add test for AID collection when joining tables.

Author: cristianberneanu

test/expected/misc.out

@@ -231,3 +231,21 @@ ERROR:  Column `id` is already marked as an AID.
 CONTEXT:  PL/pgSQL function diffix.assert_column_is_not_aid(text,text) line 20 at RAISE
 SQL statement "CALL diffix.assert_column_is_not_aid(table_name, column_name)"
 PL/pgSQL function diffix.mark_filterable(text,text) line 3 at CALL
+-- JOIN between personal tables produces multiple AIDs
+EXPLAIN VERBOSE SELECT COUNT(*) FROM test_customers c JOIN test_purchases pur ON c.id = cid;
+                                         QUERY PLAN                                         
+--------------------------------------------------------------------------------------------
+ Aggregate  (cost=72.44..72.45 rows=1 width=8)
+   Output: count(*)
+   ->  Hash Join  (cost=28.23..66.79 rows=2260 width=0)
+         Inner Unique: true
+         Hash Cond: (pur.cid = c.id)
+         ->  Seq Scan on public.test_purchases pur  (cost=0.00..32.60 rows=2260 width=4)
+               Output: pur.cid, pur.pid
+         ->  Hash  (cost=18.10..18.10 rows=810 width=4)
+               Output: c.id
+               ->  Seq Scan on public.test_customers c  (cost=0.00..18.10 rows=810 width=4)
+                     Output: c.id
+ Query Identifier: 31
+(12 rows)
+

test/sql/misc.sql

@@ -108,3 +108,6 @@ SELECT diffix.sum_noise(discount), diffix.count_noise(*) FROM test_customers;
 -- Rejects marking an AID column.
 CALL diffix.mark_not_filterable('test_customers', 'id');
 CALL diffix.mark_filterable('test_customers', 'id');
+
+-- JOIN between personal tables produces multiple AIDs
+EXPLAIN VERBOSE SELECT COUNT(*) FROM test_customers c JOIN test_purchases pur ON c.id = cid;