Add amcheck verification of heap relations belonging to btree indexes.

Add a new, optional, capability to bt_index_check() and
bt_index_parent_check():  check that each heap tuple that should have an
index entry does in fact have one.  The extra checking is performed at
the end of the existing nbtree checks.

This is implemented by using a Bloom filter data structure.  The
implementation performs set membership tests within a callback (the same
type of callback that each index AM registers for CREATE INDEX).  The
Bloom filter is populated during the initial index verification scan.

Reusing the CREATE INDEX infrastructure allows the new verification
option to automatically benefit from the heap consistency checks that
CREATE INDEX already performs.  CREATE INDEX does thorough sanity
checking of HOT chains, so the new check actually manages to detect
problems in heap-only tuples.

Author: Peter Geoghegan
Reviewed-By: Pavan Deolasee, Andres Freund
Discussion: https://postgr.es/m/CAH2-Wzm5VmG7cu1N-H=nnS57wZThoSDQU+F5dewx3o84M+jY=g@mail.gmail.com

contrib/amcheck/Makefile

@@ -4,7 +4,7 @@ MODULE_big	= amcheck
 OBJS		= verify_nbtree.o $(WIN32RES)
 
 EXTENSION = amcheck
-DATA = amcheck--1.0.sql
+DATA = amcheck--1.0--1.1.sql amcheck--1.0.sql
 PGFILEDESC = "amcheck - function for verifying relation integrity"
 
 REGRESS = check check_btree

contrib/amcheck/amcheck--1.0--1.1.sql

+/* contrib/amcheck/amcheck--1.0--1.1.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "ALTER EXTENSION amcheck UPDATE TO '1.1'" to load this file. \quit
+
+-- In order to avoid issues with dependencies when updating amcheck to 1.1,
+-- create new, overloaded versions of the 1.0 functions
+
+--
+-- bt_index_check()
+--
+CREATE FUNCTION bt_index_check(index regclass,
+    heapallindexed boolean)
+RETURNS VOID
+AS 'MODULE_PATHNAME', 'bt_index_check'
+LANGUAGE C STRICT PARALLEL RESTRICTED;
+
+--
+-- bt_index_parent_check()
+--
+CREATE FUNCTION bt_index_parent_check(index regclass,
+    heapallindexed boolean)
+RETURNS VOID
+AS 'MODULE_PATHNAME', 'bt_index_parent_check'
+LANGUAGE C STRICT PARALLEL RESTRICTED;
+
+-- Don't want these to be available to public
+REVOKE ALL ON FUNCTION bt_index_check(regclass, boolean) FROM PUBLIC;
+REVOKE ALL ON FUNCTION bt_index_parent_check(regclass, boolean) FROM PUBLIC;

contrib/amcheck/amcheck.control

 # amcheck extension
 comment = 'functions for verifying relation integrity'
-default_version = '1.0'
+default_version = '1.1'
 module_pathname = '$libdir/amcheck'
 relocatable = true

contrib/amcheck/expected/check_btree.out

@@ -18,6 +18,8 @@ RESET ROLE;
 -- above explicit permission has to be granted for that.
 GRANT EXECUTE ON FUNCTION bt_index_check(regclass) TO bttest_role;
 GRANT EXECUTE ON FUNCTION bt_index_parent_check(regclass) TO bttest_role;
+GRANT EXECUTE ON FUNCTION bt_index_check(regclass, boolean) TO bttest_role;
+GRANT EXECUTE ON FUNCTION bt_index_parent_check(regclass, boolean) TO bttest_role;
 SET ROLE bttest_role;
 SELECT bt_index_check('bttest_a_idx');
  bt_index_check 
@@ -56,8 +58,14 @@ SELECT bt_index_check('bttest_a_idx');
  
 (1 row)
 
--- more expansive test
-SELECT bt_index_parent_check('bttest_b_idx');
+-- more expansive tests
+SELECT bt_index_check('bttest_a_idx', true);
+ bt_index_check 
+----------------
+ 
+(1 row)
+
+SELECT bt_index_parent_check('bttest_b_idx', true);
  bt_index_parent_check 
 -----------------------
  

contrib/amcheck/sql/check_btree.sql

@@ -21,6 +21,8 @@ RESET ROLE;
 -- above explicit permission has to be granted for that.
 GRANT EXECUTE ON FUNCTION bt_index_check(regclass) TO bttest_role;
 GRANT EXECUTE ON FUNCTION bt_index_parent_check(regclass) TO bttest_role;
+GRANT EXECUTE ON FUNCTION bt_index_check(regclass, boolean) TO bttest_role;
+GRANT EXECUTE ON FUNCTION bt_index_parent_check(regclass, boolean) TO bttest_role;
 SET ROLE bttest_role;
 SELECT bt_index_check('bttest_a_idx');
 SELECT bt_index_parent_check('bttest_a_idx');
@@ -42,8 +44,9 @@ ROLLBACK;
 
 -- normal check outside of xact
 SELECT bt_index_check('bttest_a_idx');
--- more expansive test
-SELECT bt_index_parent_check('bttest_b_idx');
+-- more expansive tests
+SELECT bt_index_check('bttest_a_idx', true);
+SELECT bt_index_parent_check('bttest_b_idx', true);
 
 BEGIN;
 SELECT bt_index_check('bttest_a_idx');