6 files changed, 359 insertions, 2 deletions
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index e32c8925f67..89aa41b5e31 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -40,9 +40,9 @@ SUBDIRS = \
 
 
 ifeq ($(enable_injection_points),yes)
-SUBDIRS += injection_points
+SUBDIRS += injection_points gin
 else
-ALWAYS_SUBDIRS += injection_points
+ALWAYS_SUBDIRS += injection_points gin
 endif
 
 ifeq ($(with_ssl),openssl)
diff --git a/src/test/modules/gin/Makefile b/src/test/modules/gin/Makefile
new file mode 100644
index 00000000000..a7731b7fa18
--- /dev/null
+++ b/src/test/modules/gin/Makefile
@@ -0,0 +1,16 @@
+# src/test/modules/gin/Makefile
+
+EXTRA_INSTALL = src/test/modules/injection_points
+
+REGRESS = gin_incomplete_splits
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/gin
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/gin/expected/gin_incomplete_splits.out b/src/test/modules/gin/expected/gin_incomplete_splits.out
new file mode 100644
index 00000000000..9a60f8c128a
--- /dev/null
+++ b/src/test/modules/gin/expected/gin_incomplete_splits.out
@@ -0,0 +1,180 @@
+--
+-- The test uses a GIN index over int[].  The table contains arrays
+-- with integers from 1 to :next_i.  Each integer occurs exactly once,
+-- no gaps or duplicates, although the index does contain some
+-- duplicate elements because some of the inserting transactions are
+-- rolled back during the test. The exact contents of the table depend
+-- on the physical layout of the index, which in turn depends at least
+-- on the block size, so instead of check for the exact contents, we
+-- check those invariants.  :next_i psql variable is maintained at all
+-- times to hold the last inserted integer + 1.
+--
+-- This uses injection points to cause errors that leave some page
+-- splits in "incomplete" state
+create extension injection_points;
+-- Use the index for all the queries
+set enable_seqscan=off;
+-- Print a NOTICE whenever an incomplete split gets fixed
+SELECT injection_points_attach('gin-finish-incomplete-split', 'notice');
+ injection_points_attach 
+-------------------------
+ 
+(1 row)
+
+--
+-- First create the test table and some helper functions
+--
+create table gin_incomplete_splits(i int4[]) with (autovacuum_enabled = off);
+create index on gin_incomplete_splits using gin (i) with (fastupdate = off);
+-- Creates an array with all integers from $1 (inclusive) $2 (exclusive)
+create function range_array(int, int) returns int[] language sql immutable as $$
+  select array_agg(g) from generate_series($1, $2 - 1) g
+$$;
+-- Inserts an array with 'n' rows to the test table. Pass :next_i as
+-- the first argument, returns the new value for :next_i.
+create function insert_n(first_i int, n int) returns int language plpgsql as $$
+begin
+  insert into gin_incomplete_splits values (range_array(first_i, first_i+n));
+  return first_i + n;
+end;
+$$;
+-- Inserts to the table until an insert fails. Like insert_n(), returns the
+-- new value for :next_i.
+create function insert_until_fail(next_i int, step int default 1) returns int language plpgsql as $$
+declare
+  i integer;
+begin
+  -- Insert arrays with 'step' elements each, until an error occurs.
+  loop
+    begin
+      select insert_n(next_i, step) into next_i;
+    exception when others then
+      raise notice 'failed with: %', sqlerrm;
+      exit;
+    end;
+
+    -- The caller is expected to set an injection point that eventuall
+    -- causes an error. But bail out if still no error after 10000
+    -- attempts, so that we don't get stuck in an infinite loop.
+    i := i + 1;
+    if i = 10000 then
+      raise 'no error on inserts after ';
+    end if;
+  end loop;
+
+  return next_i;
+end;
+$$;
+-- Check the invariants.
+create function verify(next_i int) returns bool language plpgsql as $$
+declare
+  a integer[];
+  elem integer;
+  c integer;
+begin
+  -- Perform a scan over the trailing part of the index, where the
+  -- possible incomplete splits are. (We don't check the whole table,
+  -- because that'd be pretty slow.)
+  c := 0;
+  -- Find all arrays that overlap with the last 200 inserted integers. Or
+  -- the next 100, which shouldn't exist.
+  for a in select i from gin_incomplete_splits where i && range_array(next_i - 200, next_i + 100)
+  loop
+    -- count all elements in those arrays in the window.
+    foreach elem in ARRAY a loop
+      if elem >= next_i then
+        raise 'unexpected value % in array', elem;
+      end if;
+      if elem >= next_i - 200 then
+        c := c + 1;
+      end if;
+    end loop;
+  end loop;
+  if c <> 200 then
+    raise 'unexpected count % ', c;
+  end if;
+
+  return true;
+end;
+$$;
+-- Insert one array to get started.
+select insert_n(1, 1000) as next_i
+\gset
+select verify(:next_i);
+ verify 
+--------
+ t
+(1 row)
+
+--
+-- Test incomplete leaf split
+--
+SELECT injection_points_attach('gin-leave-leaf-split-incomplete', 'error');
+ injection_points_attach 
+-------------------------
+ 
+(1 row)
+
+select insert_until_fail(:next_i) as next_i
+\gset
+NOTICE:  failed with: error triggered for injection point gin-leave-leaf-split-incomplete
+SELECT injection_points_detach('gin-leave-leaf-split-incomplete');
+ injection_points_detach 
+-------------------------
+ 
+(1 row)
+
+-- Verify that a scan works even though there's an incomplete split
+select verify(:next_i);
+ verify 
+--------
+ t
+(1 row)
+
+-- Insert some more rows, finishing the split
+select insert_n(:next_i, 10) as next_i
+\gset
+NOTICE:  notice triggered for injection point gin-finish-incomplete-split
+-- Verify that a scan still works
+select verify(:next_i);
+ verify 
+--------
+ t
+(1 row)
+
+--
+-- Test incomplete internal page split
+--
+SELECT injection_points_attach('gin-leave-internal-split-incomplete', 'error');
+ injection_points_attach 
+-------------------------
+ 
+(1 row)
+
+select insert_until_fail(:next_i, 100) as next_i
+\gset
+NOTICE:  failed with: error triggered for injection point gin-leave-internal-split-incomplete
+SELECT injection_points_detach('gin-leave-internal-split-incomplete');
+ injection_points_detach 
+-------------------------
+ 
+(1 row)
+
+ -- Verify that a scan works even though there's an incomplete split
+select verify(:next_i);
+ verify 
+--------
+ t
+(1 row)
+
+-- Insert some more rows, finishing the split
+select insert_n(:next_i, 10) as next_i
+\gset
+NOTICE:  notice triggered for injection point gin-finish-incomplete-split
+-- Verify that a scan still works
+select verify(:next_i);
+ verify 
+--------
+ t
+(1 row)
+
diff --git a/src/test/modules/gin/meson.build b/src/test/modules/gin/meson.build
new file mode 100644
index 00000000000..9734b51de2d
--- /dev/null
+++ b/src/test/modules/gin/meson.build
@@ -0,0 +1,16 @@
+# Copyright (c) 2022-2024, PostgreSQL Global Development Group
+
+if not get_option('injection_points')
+  subdir_done()
+endif
+
+tests += {
+  'name': 'gin',
+  'sd': meson.current_source_dir(),
+  'bd': meson.current_build_dir(),
+  'regress': {
+    'sql': [
+      'gin_incomplete_splits',
+    ],
+  },
+}
diff --git a/src/test/modules/gin/sql/gin_incomplete_splits.sql b/src/test/modules/gin/sql/gin_incomplete_splits.sql
new file mode 100644
index 00000000000..4e180b25195
--- /dev/null
+++ b/src/test/modules/gin/sql/gin_incomplete_splits.sql
@@ -0,0 +1,144 @@
+--
+-- The test uses a GIN index over int[].  The table contains arrays
+-- with integers from 1 to :next_i.  Each integer occurs exactly once,
+-- no gaps or duplicates, although the index does contain some
+-- duplicate elements because some of the inserting transactions are
+-- rolled back during the test. The exact contents of the table depend
+-- on the physical layout of the index, which in turn depends at least
+-- on the block size, so instead of check for the exact contents, we
+-- check those invariants.  :next_i psql variable is maintained at all
+-- times to hold the last inserted integer + 1.
+--
+
+-- This uses injection points to cause errors that leave some page
+-- splits in "incomplete" state
+create extension injection_points;
+
+-- Use the index for all the queries
+set enable_seqscan=off;
+
+-- Print a NOTICE whenever an incomplete split gets fixed
+SELECT injection_points_attach('gin-finish-incomplete-split', 'notice');
+
+--
+-- First create the test table and some helper functions
+--
+create table gin_incomplete_splits(i int4[]) with (autovacuum_enabled = off);
+
+create index on gin_incomplete_splits using gin (i) with (fastupdate = off);
+
+-- Creates an array with all integers from $1 (inclusive) $2 (exclusive)
+create function range_array(int, int) returns int[] language sql immutable as $$
+  select array_agg(g) from generate_series($1, $2 - 1) g
+$$;
+
+-- Inserts an array with 'n' rows to the test table. Pass :next_i as
+-- the first argument, returns the new value for :next_i.
+create function insert_n(first_i int, n int) returns int language plpgsql as $$
+begin
+  insert into gin_incomplete_splits values (range_array(first_i, first_i+n));
+  return first_i + n;
+end;
+$$;
+
+-- Inserts to the table until an insert fails. Like insert_n(), returns the
+-- new value for :next_i.
+create function insert_until_fail(next_i int, step int default 1) returns int language plpgsql as $$
+declare
+  i integer;
+begin
+  -- Insert arrays with 'step' elements each, until an error occurs.
+  loop
+    begin
+      select insert_n(next_i, step) into next_i;
+    exception when others then
+      raise notice 'failed with: %', sqlerrm;
+      exit;
+    end;
+
+    -- The caller is expected to set an injection point that eventuall
+    -- causes an error. But bail out if still no error after 10000
+    -- attempts, so that we don't get stuck in an infinite loop.
+    i := i + 1;
+    if i = 10000 then
+      raise 'no error on inserts after ';
+    end if;
+  end loop;
+
+  return next_i;
+end;
+$$;
+
+-- Check the invariants.
+create function verify(next_i int) returns bool language plpgsql as $$
+declare
+  a integer[];
+  elem integer;
+  c integer;
+begin
+  -- Perform a scan over the trailing part of the index, where the
+  -- possible incomplete splits are. (We don't check the whole table,
+  -- because that'd be pretty slow.)
+  c := 0;
+  -- Find all arrays that overlap with the last 200 inserted integers. Or
+  -- the next 100, which shouldn't exist.
+  for a in select i from gin_incomplete_splits where i && range_array(next_i - 200, next_i + 100)
+  loop
+    -- count all elements in those arrays in the window.
+    foreach elem in ARRAY a loop
+      if elem >= next_i then
+        raise 'unexpected value % in array', elem;
+      end if;
+      if elem >= next_i - 200 then
+        c := c + 1;
+      end if;
+    end loop;
+  end loop;
+  if c <> 200 then
+    raise 'unexpected count % ', c;
+  end if;
+
+  return true;
+end;
+$$;
+
+-- Insert one array to get started.
+select insert_n(1, 1000) as next_i
+\gset
+select verify(:next_i);
+
+
+--
+-- Test incomplete leaf split
+--
+SELECT injection_points_attach('gin-leave-leaf-split-incomplete', 'error');
+select insert_until_fail(:next_i) as next_i
+\gset
+SELECT injection_points_detach('gin-leave-leaf-split-incomplete');
+
+-- Verify that a scan works even though there's an incomplete split
+select verify(:next_i);
+
+-- Insert some more rows, finishing the split
+select insert_n(:next_i, 10) as next_i
+\gset
+-- Verify that a scan still works
+select verify(:next_i);
+
+
+--
+-- Test incomplete internal page split
+--
+SELECT injection_points_attach('gin-leave-internal-split-incomplete', 'error');
+select insert_until_fail(:next_i, 100) as next_i
+\gset
+SELECT injection_points_detach('gin-leave-internal-split-incomplete');
+
+ -- Verify that a scan works even though there's an incomplete split
+select verify(:next_i);
+
+-- Insert some more rows, finishing the split
+select insert_n(:next_i, 10) as next_i
+\gset
+-- Verify that a scan still works
+select verify(:next_i);
diff --git a/src/test/modules/meson.build b/src/test/modules/meson.build
index 397e0906e6f..8fbe742d385 100644
--- a/src/test/modules/meson.build
+++ b/src/test/modules/meson.build
@@ -5,6 +5,7 @@ subdir('commit_ts')
 subdir('delay_execution')
 subdir('dummy_index_am')
 subdir('dummy_seclabel')
+subdir('gin')
 subdir('injection_points')
 subdir('ldap_password_func')
 subdir('libpq_pipeline')