MDEV-24653 Assertion block->page.id.page_no() == index->page failed in innobase_add_instant_try()

We may end up with an empty leaf page (containing only an ADD COLUMN
metadata record) that is not the root page.

innobase_add_instant_try(): Disable an optimization for a non-canonical
empty table that contains a metadata record somewhere else than in
the root page.

btr_pcur_store_position(): Tolerate a non-canonical empty table.

mysql-test/suite/innodb/r/instant_alter_debug.result

@@ -263,7 +263,6 @@ a	b	vb
 4	NULL	NULL
 5	NULL	NULL
 DROP TABLE t1;
-SET GLOBAL innodb_purge_rseg_truncate_frequency = @save_frequency;
 #
 # MDEV-21045 AddressSanitizer: use-after-poison in mem_heap_dup / row_log_table_get_pk_col
 #
@@ -282,3 +281,21 @@ connection default;
 SET DEBUG_SYNC='RESET';
 disconnect con2;
 DROP TABLE t1;
+#
+# MDEV-24653 Assertion block->page.id.page_no() == index->page failed
+# in innobase_add_instant_try()
+#
+SET @saved_limit = @@GLOBAL.innodb_limit_optimistic_insert_debug;
+SET GLOBAL innodb_limit_optimistic_insert_debug = 2;
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+ALTER TABLE t1 ADD COLUMN b INT;
+DELETE FROM t1;
+InnoDB		0 transactions not purged
+ALTER TABLE t1 ADD COLUMN c INT;
+SELECT * FROM t1;
+a	b	c
+DROP TABLE t1;
+SET GLOBAL innodb_limit_optimistic_insert_debug = @saved_limit;
+# End of 10.3 tests
+SET GLOBAL innodb_purge_rseg_truncate_frequency = @save_frequency;

mysql-test/suite/innodb/t/instant_alter_debug.test

@@ -292,8 +292,6 @@ CHECK TABLE t1;
 SELECT * FROM t1;
 DROP TABLE t1;
 
-SET GLOBAL innodb_purge_rseg_truncate_frequency = @save_frequency;
-
 --echo #
 --echo # MDEV-21045 AddressSanitizer: use-after-poison in mem_heap_dup / row_log_table_get_pk_col
 --echo #
@@ -319,3 +317,26 @@ SET DEBUG_SYNC='now SIGNAL update';
 SET DEBUG_SYNC='RESET';
 --disconnect con2
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-24653 Assertion block->page.id.page_no() == index->page failed
+--echo # in innobase_add_instant_try()
+--echo #
+
+SET @saved_limit = @@GLOBAL.innodb_limit_optimistic_insert_debug;
+SET GLOBAL innodb_limit_optimistic_insert_debug = 2;
+
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+ALTER TABLE t1 ADD COLUMN b INT;
+DELETE FROM t1;
+--source include/wait_all_purged.inc
+ALTER TABLE t1 ADD COLUMN c INT;
+
+SELECT * FROM t1;
+DROP TABLE t1;
+SET GLOBAL innodb_limit_optimistic_insert_debug = @saved_limit;
+
+--echo # End of 10.3 tests
+
+SET GLOBAL innodb_purge_rseg_truncate_frequency = @save_frequency;

storage/innobase/btr/btr0pcur.cc

@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2016, 2020, MariaDB Corporation.
+Copyright (c) 2016, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -128,13 +128,14 @@ btr_pcur_store_position(
 	cursor->old_stored = true;
 
 	if (page_is_empty(block->frame)) {
+		ut_ad(block->page.id.page_no() == index->page);
+empty_table:
 		/* It must be an empty index tree; NOTE that in this case
 		we do not store the modify_clock, but always do a search
 		if we restore the cursor position */
 
 		ut_a(!page_has_siblings(block->frame));
 		ut_ad(page_is_leaf(block->frame));
-		ut_ad(block->page.id.page_no() == index->page);
 
 		if (page_rec_is_supremum_low(offs)) {
 			cursor->rel_pos = BTR_PCUR_AFTER_LAST_IN_TREE;
@@ -150,7 +151,15 @@ before_first:
 		rec = page_rec_get_prev(rec);
 
 		ut_ad(!page_rec_is_infimum(rec));
-		ut_ad(!rec_is_metadata(rec, index));
+
+		if (UNIV_UNLIKELY(rec_is_metadata(rec, index))) {
+			/* The table may be empty such that it only
+			contains a metadata record, in a leaf page
+			that is not the root page. */
+			ut_ad(index->is_primary());
+			ut_ad(block->page.id.page_no() != index->page);
+			goto empty_table;
+		}
 
 		cursor->rel_pos = BTR_PCUR_AFTER;
 	} else if (page_rec_is_infimum_low(offs)) {
@@ -160,7 +169,9 @@ before_first:
 			ut_ad(!page_has_prev(block->frame));
 			rec = page_rec_get_next(rec);
 			if (page_rec_is_supremum(rec)) {
-				ut_ad(page_has_next(block->frame));
+				ut_ad(page_has_next(block->frame)
+				      || block->page.id.page_no()
+				      != index->page);
 				goto before_first;
 			}
 		}

storage/innobase/handler/handler0alter.cc

@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 2005, 2019, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2013, 2020, MariaDB Corporation.
+Copyright (c) 2013, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -4482,11 +4482,13 @@ innobase_add_instant_try(
 	const rec_t* rec = btr_pcur_get_rec(&pcur);
 	que_thr_t* thr = pars_complete_graph_for_exec(
 		NULL, trx, ctx->heap, NULL);
+	const bool is_root = block->page.id.page_no() == index->page;
 
 	dberr_t err;
 	if (rec_is_metadata(rec, index)) {
 		ut_ad(page_rec_is_user_rec(rec));
-		if (!page_has_next(block->frame)
+		if (is_root
+		    && !page_has_next(block->frame)
 		    && page_rec_is_last(rec, block->frame)) {
 			goto empty_table;
 		}
@@ -4528,7 +4530,7 @@ innobase_add_instant_try(
 		}
 		btr_pcur_close(&pcur);
 		goto func_exit;
-	} else if (page_rec_is_supremum(rec)) {
+	} else if (is_root && page_rec_is_supremum(rec)) {
 empty_table:
 		/* The table is empty. */
 		ut_ad(fil_page_index_page_check(block->frame));