MDEV-33993 Possible server hang on DROP INDEX or RENAME INDEX

commit_try_norebuild(): Add the parameter statistics_exist,
similar to commit_try_rebuild(). If the InnoDB statistics tables
did not exist, we will not attempt to update statistics later on
during the transaction.

Thanks to Matthias Leich for originally reproducing this scenario.

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

@@ -108,11 +108,11 @@ DROP TABLE t;
 # MDEV-26772 InnoDB DDL fails with DUPLICATE KEY error
 #
 create table t1(f1 int not null primary key,
-f2 int not null, index idx(f2))engine=innodb;
+f2 int not null, index idx(f2), index i(f2,f1))engine=innodb;
 insert into t1 values(1, 1);
 connect con1,localhost,root,,,;
 SET DEBUG_SYNC='before_delete_table_stats SIGNAL blocked WAIT_FOR go';
-SET innodb_lock_wait_timeout=0;
+SET STATEMENT innodb_lock_wait_timeout=0 FOR
 ALTER TABLE t1 FORCE, ALGORITHM=COPY;
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR blocked';
@@ -124,6 +124,17 @@ connection con1;
 connection default;
 COMMIT;
 SET DEBUG_SYNC=RESET;
+RENAME TABLE mysql.innodb_table_stats TO mysql.innodb_table_stats_hidden;
+connection con1;
+SET DEBUG_SYNC='innodb_commit_inplace_before_lock SIGNAL blocked WAIT_FOR go';
+ALTER TABLE t1 DROP INDEX i;
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR blocked';
+RENAME TABLE mysql.innodb_table_stats_hidden TO mysql.innodb_table_stats;
+SET DEBUG_SYNC='now SIGNAL go';
+connection con1;
+connection default;
+SET DEBUG_SYNC=RESET;
 connection con1;
 ALTER TABLE t1 RENAME KEY idx TO idx1, ALGORITHM=COPY;
 disconnect con1;

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

@@ -144,15 +144,14 @@ DROP TABLE t;
 --echo #
 
 create table t1(f1 int not null primary key,
-
-                f2 int not null, index idx(f2))engine=innodb;
+                f2 int not null, index idx(f2), index i(f2,f1))engine=innodb;
 
 insert into t1 values(1, 1);
 
 connect(con1,localhost,root,,,);
 SET DEBUG_SYNC='before_delete_table_stats SIGNAL blocked WAIT_FOR go';
-SET innodb_lock_wait_timeout=0;
-send ALTER TABLE t1 FORCE, ALGORITHM=COPY;
+send SET STATEMENT innodb_lock_wait_timeout=0 FOR
+ALTER TABLE t1 FORCE, ALGORITHM=COPY;
 
 connection default;
 SET DEBUG_SYNC='now WAIT_FOR blocked';
@@ -167,6 +166,21 @@ connection default;
 COMMIT;
 SET DEBUG_SYNC=RESET;
 
+RENAME TABLE mysql.innodb_table_stats TO mysql.innodb_table_stats_hidden;
+connection con1;
+SET DEBUG_SYNC='innodb_commit_inplace_before_lock SIGNAL blocked WAIT_FOR go';
+send ALTER TABLE t1 DROP INDEX i;
+
+connection default;
+SET DEBUG_SYNC='now WAIT_FOR blocked';
+RENAME TABLE mysql.innodb_table_stats_hidden TO mysql.innodb_table_stats;
+SET DEBUG_SYNC='now SIGNAL go';
+
+connection con1;
+reap;
+connection default;
+SET DEBUG_SYNC=RESET;
+
 connection con1;
 ALTER TABLE t1 RENAME KEY idx TO idx1, ALGORITHM=COPY;
 disconnect con1;

storage/innobase/handler/handler0alter.cc

@@ -10228,6 +10228,7 @@ when rebuilding the table.
 @param ctx In-place ALTER TABLE context
 @param altered_table MySQL table that is being altered
 @param old_table MySQL table as it is before the ALTER operation
+@param statistics_exist whether to update InnoDB persistent statistics
 @param trx Data dictionary transaction
 @param table_name Table name in MySQL
 @retval true Failure
@@ -10501,6 +10502,7 @@ when not rebuilding the table.
 @param ha_alter_info Data used during in-place alter
 @param ctx In-place ALTER TABLE context
 @param old_table MySQL table as it is before the ALTER operation
+@param statistics_exist whether to update InnoDB persistent statistics
 @param trx Data dictionary transaction
 @param table_name Table name in MySQL
 @retval true Failure
@@ -10514,6 +10516,7 @@ commit_try_norebuild(
 	ha_innobase_inplace_ctx*ctx,
 	TABLE*			altered_table,
 	const TABLE*		old_table,
+	bool			statistics_exist,
 	trx_t*			trx,
 	const char*		table_name)
 {
@@ -10628,6 +10631,10 @@ commit_try_norebuild(
 			goto handle_error;
 		}
 
+		if (!statistics_exist) {
+			continue;
+		}
+
 		error = dict_stats_delete_from_index_stats(db, table,
 							   index->name, trx);
 		switch (error) {
@@ -10639,7 +10646,8 @@ commit_try_norebuild(
 		}
 	}
 
-	if (const size_t size = ha_alter_info->rename_keys.size()) {
+	if (!statistics_exist) {
+	} else if (const size_t size = ha_alter_info->rename_keys.size()) {
 		char tmp_name[5];
 		char db[MAX_DB_UTF8_LEN], table[MAX_TABLE_UTF8_LEN];
 
@@ -11386,6 +11394,8 @@ ha_innobase::commit_inplace_alter_table(
 		}
 	}
 
+	DEBUG_SYNC(m_user_thd, "innodb_commit_inplace_before_lock");
+
 	DBUG_EXECUTE_IF("stats_lock_fail",
 			error = DB_LOCK_WAIT_TIMEOUT;
 			trx_rollback_for_mysql(trx););
@@ -11469,7 +11479,9 @@ ha_innobase::commit_inplace_alter_table(
 				goto fail;
 			}
 		} else if (commit_try_norebuild(ha_alter_info, ctx,
-						altered_table, table, trx,
+						altered_table, table,
+						table_stats && index_stats,
+						trx,
 						table_share->table_name.str)) {
 			goto fail;
 		}