Fix TRUNCATE .. CASCADE on partitions

When running TRUNCATE CASCADE on a child of a partitioned table
referenced by another partitioned table, the truncate was not applied to
partitions of the referencing table; this could leave rows violating the
constraint in the referencing partitioned table.  Repair by walking the
pg_constraint chain all the way up to the topmost referencing table.

Note: any partitioned tables containing FKs that reference other
partitioned tables should be checked for possible violating rows, if
TRUNCATE has occurred in partitions of the referenced table.

Reported-by: Christophe Courtois
Author: Jehan-Guillaume de Rorthais
Discussion: https://postgr.es/m/20200204183906.115f693e@firost

src/test/regress/expected/truncate.out

@@ -542,3 +542,53 @@ SELECT * FROM tp_chk_data();
 
 DROP TABLE truncprim, truncpart;
 DROP FUNCTION tp_ins_data(), tp_chk_data();
+-- test cascade when referencing a partitioned table
+CREATE TABLE trunc_a (a INT PRIMARY KEY) PARTITION BY RANGE (a);
+CREATE TABLE trunc_a1 PARTITION OF trunc_a FOR VALUES FROM (0) TO (10);
+CREATE TABLE trunc_a2 PARTITION OF trunc_a FOR VALUES FROM (10) TO (20)
+  PARTITION BY RANGE (a);
+CREATE TABLE trunc_a21 PARTITION OF trunc_a2 FOR VALUES FROM (10) TO (12);
+CREATE TABLE trunc_a22 PARTITION OF trunc_a2 FOR VALUES FROM (12) TO (16);
+CREATE TABLE trunc_a2d PARTITION OF trunc_a2 DEFAULT;
+CREATE TABLE trunc_a3 PARTITION OF trunc_a FOR VALUES FROM (20) TO (30);
+INSERT INTO trunc_a VALUES (0), (5), (10), (15), (20), (25);
+-- truncate a partition cascading to a table
+CREATE TABLE ref_b (
+    b INT PRIMARY KEY,
+    a INT REFERENCES trunc_a(a) ON DELETE CASCADE
+);
+INSERT INTO ref_b VALUES (10, 0), (50, 5), (100, 10), (150, 15);
+TRUNCATE TABLE trunc_a1 CASCADE;
+NOTICE:  truncate cascades to table "ref_b"
+SELECT a FROM ref_b;
+ a 
+---
+(0 rows)
+
+DROP TABLE ref_b;
+-- truncate a partition cascading to a partitioned table
+CREATE TABLE ref_c (
+    c INT PRIMARY KEY,
+    a INT REFERENCES trunc_a(a) ON DELETE CASCADE
+) PARTITION BY RANGE (c);
+CREATE TABLE ref_c1 PARTITION OF ref_c FOR VALUES FROM (100) TO (200);
+CREATE TABLE ref_c2 PARTITION OF ref_c FOR VALUES FROM (200) TO (300);
+INSERT INTO ref_c VALUES (100, 10), (150, 15), (200, 20), (250, 25);
+TRUNCATE TABLE trunc_a21 CASCADE;
+NOTICE:  truncate cascades to table "ref_c"
+NOTICE:  truncate cascades to table "ref_c1"
+NOTICE:  truncate cascades to table "ref_c2"
+SELECT a as "from table ref_c" FROM ref_c;
+ from table ref_c 
+------------------
+(0 rows)
+
+SELECT a as "from table trunc_a" FROM trunc_a ORDER BY a;
+ from table trunc_a 
+--------------------
+                 15
+                 20
+                 25
+(3 rows)
+
+DROP TABLE trunc_a, ref_c;

src/test/regress/sql/truncate.sql

@@ -289,3 +289,41 @@ TRUNCATE TABLE truncpart;
 SELECT * FROM tp_chk_data();
 DROP TABLE truncprim, truncpart;
 DROP FUNCTION tp_ins_data(), tp_chk_data();
+
+-- test cascade when referencing a partitioned table
+CREATE TABLE trunc_a (a INT PRIMARY KEY) PARTITION BY RANGE (a);
+CREATE TABLE trunc_a1 PARTITION OF trunc_a FOR VALUES FROM (0) TO (10);
+CREATE TABLE trunc_a2 PARTITION OF trunc_a FOR VALUES FROM (10) TO (20)
+  PARTITION BY RANGE (a);
+CREATE TABLE trunc_a21 PARTITION OF trunc_a2 FOR VALUES FROM (10) TO (12);
+CREATE TABLE trunc_a22 PARTITION OF trunc_a2 FOR VALUES FROM (12) TO (16);
+CREATE TABLE trunc_a2d PARTITION OF trunc_a2 DEFAULT;
+CREATE TABLE trunc_a3 PARTITION OF trunc_a FOR VALUES FROM (20) TO (30);
+INSERT INTO trunc_a VALUES (0), (5), (10), (15), (20), (25);
+
+-- truncate a partition cascading to a table
+CREATE TABLE ref_b (
+    b INT PRIMARY KEY,
+    a INT REFERENCES trunc_a(a) ON DELETE CASCADE
+);
+INSERT INTO ref_b VALUES (10, 0), (50, 5), (100, 10), (150, 15);
+
+TRUNCATE TABLE trunc_a1 CASCADE;
+SELECT a FROM ref_b;
+
+DROP TABLE ref_b;
+
+-- truncate a partition cascading to a partitioned table
+CREATE TABLE ref_c (
+    c INT PRIMARY KEY,
+    a INT REFERENCES trunc_a(a) ON DELETE CASCADE
+) PARTITION BY RANGE (c);
+CREATE TABLE ref_c1 PARTITION OF ref_c FOR VALUES FROM (100) TO (200);
+CREATE TABLE ref_c2 PARTITION OF ref_c FOR VALUES FROM (200) TO (300);
+INSERT INTO ref_c VALUES (100, 10), (150, 15), (200, 20), (250, 25);
+
+TRUNCATE TABLE trunc_a21 CASCADE;
+SELECT a as "from table ref_c" FROM ref_c;
+SELECT a as "from table trunc_a" FROM trunc_a ORDER BY a;
+
+DROP TABLE trunc_a, ref_c;