MDEV-35059 ALTER TABLE...IMPORT TABLESPACE with FULLTEXT SEARCH may corrupt the adaptive hash index

build_fts_hidden_table(): Correct a mistake that had been made in
commit 903ae300 (MDEV-30655).

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

+SET @save_adaptive=@@GLOBAL.innodb_adaptive_hash_index;
+SET GLOBAL innodb_adaptive_hash_index=ON;
 call mtr.add_suppression("InnoDB: Added system generated FTS_DOC_ID and FTS_DOC_ID_INDEX while importing the tablespace");
 CREATE TABLE t1(f1 INT NOT NULL PRIMARY KEY,
 f2 CHAR(2) not null, fulltext f_idx(f2),
@@ -9,7 +11,7 @@ INSERT INTO t1(f1, f2) SELECT seq, "si" FROM seq_2_to_256;
 ALTER TABLE t1 ADD COLUMN f6 INT NOT NULL;
 ALTER TABLE t1 DROP COLUMN f6;
 ALTER TABLE t1 DROP INDEX f_idx;
-connect con1,localhost,root,,;
+connect block_purge,localhost,root,,;
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
 connection default;
 DELETE FROM t1 WHERE f1 > 1;
@@ -22,6 +24,7 @@ UNLOCK TABLES;
 Warnings:
 Warning	1235	This version of MariaDB doesn't yet support 'FLUSH TABLES on a table that had an FTS index, created on a hidden column, the auxiliary tables haven't been dropped as yet. FTS auxiliary tables will not be flushed.'
 DROP TABLE t1;
+disconnect block_purge;
 CREATE TABLE t1(f1 INT NOT NULL PRIMARY KEY,
 f2 CHAR(2) not null,
 f3 INT as (f1) VIRTUAL, INDEX(f3),
@@ -43,3 +46,4 @@ t1	CREATE TABLE `t1` (
   KEY `f4` (`f4`)
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 DROP TABLE t1;
+SET GLOBAL innodb_adaptive_hash_index=@save_adaptive;

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

 --source include/have_innodb.inc
 --source include/have_sequence.inc
+
+--error 0,ER_UNKNOWN_SYSTEM_VARIABLE
+SET @save_adaptive=@@GLOBAL.innodb_adaptive_hash_index;
+--error 0,ER_UNKNOWN_SYSTEM_VARIABLE
+SET GLOBAL innodb_adaptive_hash_index=ON;
+
 # Table with virtual, fulltext, instant add, instant drop column
 # and purgeable rows
 call mtr.add_suppression("InnoDB: Added system generated FTS_DOC_ID and FTS_DOC_ID_INDEX while importing the tablespace");
@@ -13,7 +19,7 @@ INSERT INTO t1(f1, f2) SELECT seq, "si" FROM seq_2_to_256;
 ALTER TABLE t1 ADD COLUMN f6 INT NOT NULL;
 ALTER TABLE t1 DROP COLUMN f6;
 ALTER TABLE t1 DROP INDEX f_idx;
-connect(con1,localhost,root,,);
+connect(block_purge,localhost,root,,);
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
 
 connection default;
@@ -26,6 +32,7 @@ ib_backup_tablespaces("test", "t1");
 EOF
 UNLOCK TABLES;
 DROP TABLE t1;
+disconnect block_purge;
 
 CREATE TABLE t1(f1 INT NOT NULL PRIMARY KEY,
 		f2 CHAR(2) not null,
@@ -44,3 +51,5 @@ ALTER TABLE t1 IMPORT TABLESPACE;
 --enable_warnings
 SHOW CREATE TABLE t1;
 DROP TABLE t1;
+--error 0,ER_UNKNOWN_SYSTEM_VARIABLE
+SET GLOBAL innodb_adaptive_hash_index=@save_adaptive;

storage/innobase/row/row0import.cc

@@ -3335,7 +3335,9 @@ static dict_table_t *build_fts_hidden_table(
       new_index->fields[old_index->n_fields].fixed_len= sizeof(doc_id_t);
     }
 
-    new_index->search_info= old_index->search_info;
+#ifdef BTR_CUR_HASH_ADAPT
+    new_index->search_info= btr_search_info_create(new_index->heap);
+#endif /* BTR_CUR_HASH_ADAPT */
     UT_LIST_ADD_LAST(new_index->table->indexes, new_index);
     old_index= UT_LIST_GET_NEXT(indexes, old_index);
     if (UT_LIST_GET_LEN(new_table->indexes)