MDEV-33400 Adaptive hash index corruption after DISCARD TABLESPACE

row_discard_tablespace(): Do not invoke dict_index_t::clear_instant_alter()
because that would corrupt any adaptive hash index entries in the table.

row_import_for_mysql(): Invoke dict_index_t::clear_instant_alter()
after detaching any adaptive hash index entries.

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

@@ -10,3 +10,19 @@ ALTER TABLE imp_t1 IMPORT TABLESPACE;
 ERROR HY000: Schema mismatch (ROW_FORMAT mismatch)
 DROP TABLE imp_t1, t1;
 SET GLOBAL innodb_checksum_algorithm=@save_innodb_checksum_algorithm;
+#
+# MDEV-33400 Adaptive hash index corruption after DISCARD TABLESPACE
+#
+SET @save_adaptive=@@GLOBAL.innodb_adaptive_hash_index;
+SET GLOBAL innodb_adaptive_hash_index=ON;
+CREATE TABLE t (a INT PRIMARY KEY) ENGINE=INNODB;
+INSERT INTO t SELECT * FROM seq_1_to_131;
+ALTER TABLE t ADD hid INT DEFAULT 2;
+INSERT INTO t VALUES (251,1);
+ALTER TABLE t DISCARD TABLESPACE;
+CHECK TABLE mysql.innodb_table_stats;
+Table	Op	Msg_type	Msg_text
+mysql.innodb_table_stats	check	status	OK
+DROP TABLE t;
+SET GLOBAL innodb_adaptive_hash_index=@save_adaptive;
+# End of 10.4 tests

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

 --source include/have_innodb.inc
+--source include/have_sequence.inc
 
 call mtr.add_suppression("Index for table 'imp_t1' is corrupt; try to repair it");
 
@@ -17,3 +18,21 @@ ALTER TABLE imp_t1 IMPORT TABLESPACE;
 DROP TABLE imp_t1, t1;
 
 SET GLOBAL innodb_checksum_algorithm=@save_innodb_checksum_algorithm;
+
+--echo #
+--echo # MDEV-33400 Adaptive hash index corruption after DISCARD TABLESPACE
+--echo #
+
+SET @save_adaptive=@@GLOBAL.innodb_adaptive_hash_index;
+SET GLOBAL innodb_adaptive_hash_index=ON;
+
+CREATE TABLE t (a INT PRIMARY KEY) ENGINE=INNODB;
+INSERT INTO t SELECT * FROM seq_1_to_131;
+ALTER TABLE t ADD hid INT DEFAULT 2;
+INSERT INTO t VALUES (251,1);
+ALTER TABLE t DISCARD TABLESPACE;
+CHECK TABLE mysql.innodb_table_stats;
+DROP TABLE t;
+SET GLOBAL innodb_adaptive_hash_index=@save_adaptive;
+
+--echo # End of 10.4 tests

storage/innobase/row/row0import.cc

@@ -4383,6 +4383,23 @@ row_import_for_mysql(
 
 	ibuf_delete_for_discarded_space(table->space_id);
 
+#ifdef BTR_CUR_HASH_ADAPT
+	/* On DISCARD TABLESPACE, we did not drop any adaptive hash
+	index entries. If we replaced the discarded tablespace with a
+	smaller one here, there could still be some adaptive hash
+	index entries that point to cached garbage pages in the buffer
+	pool, because PageConverter::operator() only evicted those
+	pages that were replaced by the imported pages. We must
+	detach any remaining adaptive hash index entries, because the
+	adaptive hash index must be a subset of the table contents;
+	false positives are not tolerated. */
+	for (dict_index_t* index = UT_LIST_GET_FIRST(table->indexes); index;
+	     index = UT_LIST_GET_NEXT(indexes, index)) {
+		index = index->clone_if_needed();
+	}
+#endif /* BTR_CUR_HASH_ADAPT */
+	UT_LIST_GET_FIRST(table->indexes)->clear_instant_alter();
+
 	trx_start_if_not_started(prebuilt->trx, true);
 
 	trx = trx_create();
@@ -4540,21 +4557,6 @@ row_import_for_mysql(
 
 	DBUG_EXECUTE_IF("ib_import_reset_space_and_lsn_failure",
 			err = DB_TOO_MANY_CONCURRENT_TRXS;);
-#ifdef BTR_CUR_HASH_ADAPT
-	/* On DISCARD TABLESPACE, we did not drop any adaptive hash
-	index entries. If we replaced the discarded tablespace with a
-	smaller one here, there could still be some adaptive hash
-	index entries that point to cached garbage pages in the buffer
-	pool, because PageConverter::operator() only evicted those
-	pages that were replaced by the imported pages. We must
-	detach any remaining adaptive hash index entries, because the
-	adaptive hash index must be a subset of the table contents;
-	false positives are not tolerated. */
-	for (dict_index_t* index = UT_LIST_GET_FIRST(table->indexes); index;
-	     index = UT_LIST_GET_NEXT(indexes, index)) {
-		index = index->clone_if_needed();
-	}
-#endif /* BTR_CUR_HASH_ADAPT */
 
 	if (err != DB_SUCCESS) {
 		char	table_name[MAX_FULL_NAME_LEN + 1];

storage/innobase/row/row0mysql.cc

@@ -3047,7 +3047,6 @@ row_discard_tablespace(
 	dict_table_change_id_in_cache(table, new_id);
 
 	dict_index_t* index = UT_LIST_GET_FIRST(table->indexes);
-	if (index) index->clear_instant_alter();
 
 	/* Reset the root page numbers. */
 	for (; index; index = UT_LIST_GET_NEXT(indexes, index)) {