Rewrite DROP's dependency traversal algorithm into an honest two-pass

algorithm, replacing the original intention of a one-pass search, which
had been hacked up over time to be partially two-pass in hopes of handling
various corner cases better.  It still wasn't quite there, especially as
regards emitting unwanted NOTICE messages.  More importantly, this approach
lets us fix a number of open bugs concerning concurrent DROP scenarios,
because we can take locks during the first pass and avoid traversing to
dependent objects that were just deleted by someone else.

There is more that can be done here, but I'll go ahead and commit the
base patch before working on the options.

1 files changed, 33 insertions, 62 deletions

diff --git a/src/test/regress/expected/create_view.out b/src/test/regress/expected/create_view.out
index 0ef4bffe0b..3eae7e90cc 100644
--- a/src/test/regress/expected/create_view.out
+++ b/src/test/regress/expected/create_view.out
@@ -237,72 +237,43 @@ And relnamespace IN (SELECT OID FROM pg_namespace WHERE nspname LIKE 'pg_temp%')
 (1 row)
 
 DROP SCHEMA temp_view_test CASCADE;
-NOTICE:  drop cascades to view temp_view_test.v9
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v9
-NOTICE:  drop cascades to sequence temp_view_test.seq1
-NOTICE:  drop cascades to view temp_view_test.v8
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v8
-NOTICE:  drop cascades to view temp_view_test.v7
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v7
-NOTICE:  drop cascades to view temp_view_test.v6
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v6
-NOTICE:  drop cascades to view temp_view_test.v5
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v5
-NOTICE:  drop cascades to view temp_view_test.v4
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v4
-NOTICE:  drop cascades to view temp_view_test.v3
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v3
-NOTICE:  drop cascades to view temp_view_test.v2
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v2
-NOTICE:  drop cascades to view temp_view_test.v1
-NOTICE:  drop cascades to rule _RETURN on view temp_view_test.v1
-NOTICE:  drop cascades to table temp_view_test.base_table2
-NOTICE:  drop cascades to rule _RETURN on view v5_temp
-NOTICE:  drop cascades to view v5_temp
 NOTICE:  drop cascades to table temp_view_test.base_table
-NOTICE:  drop cascades to rule _RETURN on view v9_temp
-NOTICE:  drop cascades to view v9_temp
-NOTICE:  drop cascades to rule _RETURN on view v8_temp
-NOTICE:  drop cascades to view v8_temp
-NOTICE:  drop cascades to rule _RETURN on view v6_temp
-NOTICE:  drop cascades to view v6_temp
-NOTICE:  drop cascades to rule _RETURN on view v4_temp
-NOTICE:  drop cascades to view v4_temp
-NOTICE:  drop cascades to rule _RETURN on view v2_temp
-NOTICE:  drop cascades to view v2_temp
-NOTICE:  drop cascades to rule _RETURN on view v11_temp
-NOTICE:  drop cascades to view v11_temp
-NOTICE:  drop cascades to rule _RETURN on view v12_temp
-NOTICE:  drop cascades to view v12_temp
-NOTICE:  drop cascades to rule _RETURN on view v7_temp
 NOTICE:  drop cascades to view v7_temp
-NOTICE:  drop cascades to rule _RETURN on view v10_temp
 NOTICE:  drop cascades to view v10_temp
+NOTICE:  drop cascades to view v11_temp
+NOTICE:  drop cascades to view v12_temp
+NOTICE:  drop cascades to view v2_temp
+NOTICE:  drop cascades to view v4_temp
+NOTICE:  drop cascades to view v6_temp
+NOTICE:  drop cascades to view v8_temp
+NOTICE:  drop cascades to view v9_temp
+NOTICE:  drop cascades to table temp_view_test.base_table2
+NOTICE:  drop cascades to view v5_temp
+NOTICE:  drop cascades to view temp_view_test.v1
+NOTICE:  drop cascades to view temp_view_test.v2
+NOTICE:  drop cascades to view temp_view_test.v3
+NOTICE:  drop cascades to view temp_view_test.v4
+NOTICE:  drop cascades to view temp_view_test.v5
+NOTICE:  drop cascades to view temp_view_test.v6
+NOTICE:  drop cascades to view temp_view_test.v7
+NOTICE:  drop cascades to view temp_view_test.v8
+NOTICE:  drop cascades to sequence temp_view_test.seq1
+NOTICE:  drop cascades to view temp_view_test.v9
 DROP SCHEMA testviewschm2 CASCADE;
-NOTICE:  drop cascades to view pubview
-NOTICE:  drop cascades to rule _RETURN on view pubview
-NOTICE:  drop cascades to table tbl4
-NOTICE:  drop cascades to rule _RETURN on view mytempview
-NOTICE:  drop cascades to view mytempview
-NOTICE:  drop cascades to table tbl3
-NOTICE:  drop cascades to table tbl2
-NOTICE:  drop cascades to table tbl1
-NOTICE:  drop cascades to view nontemp4
-NOTICE:  drop cascades to rule _RETURN on view nontemp4
-NOTICE:  drop cascades to view nontemp3
-NOTICE:  drop cascades to rule _RETURN on view nontemp3
-NOTICE:  drop cascades to view nontemp2
-NOTICE:  drop cascades to rule _RETURN on view nontemp2
-NOTICE:  drop cascades to view nontemp1
-NOTICE:  drop cascades to rule _RETURN on view nontemp1
-NOTICE:  drop cascades to table t2
 NOTICE:  drop cascades to table t1
-NOTICE:  drop cascades to rule _RETURN on view temporal4
-NOTICE:  drop cascades to view temporal4
-NOTICE:  drop cascades to rule _RETURN on view temporal3
-NOTICE:  drop cascades to view temporal3
-NOTICE:  drop cascades to rule _RETURN on view temporal2
-NOTICE:  drop cascades to view temporal2
-NOTICE:  drop cascades to rule _RETURN on view temporal1
 NOTICE:  drop cascades to view temporal1
+NOTICE:  drop cascades to view temporal2
+NOTICE:  drop cascades to view temporal3
+NOTICE:  drop cascades to view temporal4
+NOTICE:  drop cascades to table t2
+NOTICE:  drop cascades to view nontemp1
+NOTICE:  drop cascades to view nontemp2
+NOTICE:  drop cascades to view nontemp3
+NOTICE:  drop cascades to view nontemp4
+NOTICE:  drop cascades to table tbl1
+NOTICE:  drop cascades to table tbl2
+NOTICE:  drop cascades to table tbl3
+NOTICE:  drop cascades to table tbl4
+NOTICE:  drop cascades to view mytempview
+NOTICE:  drop cascades to view pubview
 SET search_path to public;