MDEV-25265: ALTER TABLE...IMPORT TABLESPACE fails after DROP INDEX

A side effect of the MDEV-24589 bug fix is that if
FLUSH TABLE...FOR EXPORT is initiated before the history of an
earlier DROP INDEX operation has been purged, then the data file
will contain allocated pages that belonged to the dropped indexes.
These pages would never be freed after a subsequent IMPORT TABLESPACE.

We will work around this regression by making IMPORT TABLESPACE
tolerate pages that refer to an unknown index.

mysql-test/suite/innodb/r/innodb-wl5522-debug.result

@@ -8,6 +8,7 @@ call mtr.add_suppression("InnoDB: Cannot calculate statistics for table .*");
 call mtr.add_suppression("InnoDB: Page 0 at offset 0 looks corrupted in file");
 call mtr.add_suppression("InnoDB: Page for tablespace ");
 call mtr.add_suppression("InnoDB: Invalid FSP_SPACE_FLAGS=");
+call mtr.add_suppression("InnoDB: Unknown index id .* on page");
 FLUSH TABLES;
 SET GLOBAL innodb_file_per_table = 1;
 CREATE TABLE t1 (c1 INT) ENGINE = InnoDB;

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

@@ -583,10 +583,14 @@ DROP TABLE t1, parent;
 --echo #BUG#21514135 SCHEMA MISMATCH ERROR WHEN IMPORTING TABLESPACE AFTER
 --echo #DROPPING AN INDEX
 --echo #
+
+--disable_query_log
+call mtr.add_suppression("\\[Warning\\] InnoDB: Unknown index id .* on page");
+--enable_query_log
+
 let $source_db = source_db;
 let $dest_db = dest_db;
 
---source include/default_charset.inc
 SET NAMES utf8mb4;
 
 eval CREATE DATABASE $source_db;

mysql-test/suite/innodb/t/innodb-wl5522-debug.test

@@ -28,6 +28,7 @@ call mtr.add_suppression("InnoDB: Cannot calculate statistics for table .*");
 call mtr.add_suppression("InnoDB: Page 0 at offset 0 looks corrupted in file");
 call mtr.add_suppression("InnoDB: Page for tablespace ");
 call mtr.add_suppression("InnoDB: Invalid FSP_SPACE_FLAGS=");
+call mtr.add_suppression("InnoDB: Unknown index id .* on page");
 FLUSH TABLES;
 
 let MYSQLD_DATADIR =`SELECT @@datadir`;

mysql-test/suite/innodb_zip/r/wl5522_debug_zip.result

@@ -3,6 +3,12 @@ call mtr.add_suppression("InnoDB: Cannot calculate statistics for table .* becau
 call mtr.add_suppression("InnoDB: Page 0 at offset 0 looks corrupted in file");
 call mtr.add_suppression("InnoDB: Page for tablespace ");
 call mtr.add_suppression("InnoDB: Invalid FSP_SPACE_FLAGS=0x");
+call mtr.add_suppression("InnoDB: Unknown index id .* on page");
+call mtr.add_suppression("InnoDB: Operating system error number");
+call mtr.add_suppression("InnoDB: The error means");
+call mtr.add_suppression("InnoDB: If you are installing InnoDB");
+call mtr.add_suppression("InnoDB: Cannot open datafile .*t1\\.ibd");
+call mtr.add_suppression("InnoDB: Ignoring tablespace for `test`\\.`t1`");
 FLUSH TABLES;
 SET SESSION innodb_strict_mode=1;
 CREATE TABLE t1 (c1 INT) ENGINE = Innodb

mysql-test/suite/innodb_zip/t/wl5522_debug_zip.test

@@ -19,6 +19,12 @@ call mtr.add_suppression("InnoDB: Cannot calculate statistics for table .* becau
 call mtr.add_suppression("InnoDB: Page 0 at offset 0 looks corrupted in file");
 call mtr.add_suppression("InnoDB: Page for tablespace ");
 call mtr.add_suppression("InnoDB: Invalid FSP_SPACE_FLAGS=0x");
+call mtr.add_suppression("InnoDB: Unknown index id .* on page");
+call mtr.add_suppression("InnoDB: Operating system error number");
+call mtr.add_suppression("InnoDB: The error means");
+call mtr.add_suppression("InnoDB: If you are installing InnoDB");
+call mtr.add_suppression("InnoDB: Cannot open datafile .*t1\\.ibd");
+call mtr.add_suppression("InnoDB: Ignoring tablespace for `test`\\.`t1`");
 FLUSH TABLES;
 
 let MYSQLD_DATADIR =`SELECT @@datadir`;

storage/innobase/row/row0import.cc

 /*****************************************************************************
 
 Copyright (c) 2012, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2020, MariaDB Corporation.
+Copyright (c) 2015, 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
@@ -1880,38 +1880,33 @@ dberr_t
 PageConverter::update_index_page(
 	buf_block_t*	block) UNIV_NOTHROW
 {
-	index_id_t	id;
-	buf_frame_t*	page = block->frame;
 	const page_id_t page_id(block->page.id());
 
 	if (is_free(page_id.page_no())) {
 		return(DB_SUCCESS);
-	} else if ((id = btr_page_get_index_id(page)) != m_index->m_id) {
+	}
+
+	buf_frame_t* page = block->frame;
+	const index_id_t id = btr_page_get_index_id(page);
 
-		row_index_t*	index = find_index(id);
+	if (id != m_index->m_id) {
+		row_index_t* index = find_index(id);
 
 		if (UNIV_UNLIKELY(!index)) {
-			ib::error() << "Page for tablespace " << m_space
-				<< " is index page with id " << id
-				<< " but that index is not found from"
-				<< " configuration file. Current index name "
-				<< m_index->m_name << " and id " <<  m_index->m_id;
-			m_index = 0;
-			return(DB_CORRUPTION);
+			ib::warn() << "Unknown index id " << id
+				   << " on page " << page_id.page_no();
+			return DB_SUCCESS;
 		}
 
-		/* Update current index */
 		m_index = index;
 	}
 
 	/* If the .cfg file is missing and there is an index mismatch
 	then ignore the error. */
-	if (m_cfg->m_missing && (m_index == 0 || m_index->m_srv_index == 0)) {
+	if (m_cfg->m_missing && !m_index->m_srv_index) {
 		return(DB_SUCCESS);
 	}
 
-
-
 	if (m_index && page_id.page_no() == m_index->m_page_no) {
 		byte *b = FIL_PAGE_DATA + PAGE_BTR_SEG_LEAF + FSEG_HDR_SPACE
 			+ page;