Database error after server move

[itilm]

I am getting data base error on new thread

I have run Rebuild Search Index But result was same Please help me

If i Select Remove Fulltext Indexes to NO Every thing start working fine

can any one also explain what Fulltext indexes do ?

nvalid SQL:

SELECT thread.threadid, MATCH(thread.title) AGAINST ('Assalam o alikum') AS score
FROM thread AS thread

WHERE MATCH(thread.title) AGAINST ('Assalam o alikum')
AND thread.open <> 10


LIMIT 5;

MySQL Error : Can't find FULLTEXT index matching the column list
Error Number : 1191
Request Date : Saturday, July 7th 2018 @ 06:50:45 AM
Error Date : Saturday, July 7th 2018 @ 06:50:45 AM
Script : http://www.domain.com/newthread.php?do=postthread&f=49
Referrer : http://www.domain.com/newthread.php?do=newthread&f=49
IP Address :
Username : username
Classname : vB_Database_MySQLi
MySQL Version : 10.2.16-MariaDB
Server :
User Agent :


Stack Trace:

#0 vB_Database->halt() called in [path]/includes/class_core.php on line 1254
#1 vB_Database_MySQLi->execute_query() called in [path]/includes/class_core.php on line 479
#2 vB_Database->query_read_slave() called in [path]/includes/functions_search.php on line 368
#3 fetch_similar_threads() called in [path]/includes/class_dm_threadpost.php on line 1174
#4 vB_DataManager_Thread->pre_save() called in [path]/includes/class_dm_threadpost.php on line 1614
#5 vB_DataManager_Thread_FirstPost->pre_save() called in [path]/includes/functions_newpost.php on line 468
#6 build_new_post() called in [path]/newthread.php on line 216