Closes #833: Return ERR when receiving 'LOAD DATA LOCAL INFILE' to let client know operation is unsupported

lib/MySQL_Session.cpp

@@ -1326,6 +1326,19 @@ bool MySQL_Session::handler_special_queries(PtrSize_t *pkt) {
 		l_free(pkt->size,pkt->ptr);
 		return true;
 	}
+	// 'LOAD DATA LOCAL INFILE' is unsupported. We report an specific error to inform clients about this fact. For more context see #833.
+	if ( (pkt->size >= 22 + 5) && (strncasecmp((char *)"LOAD DATA LOCAL INFILE",(char *)pkt->ptr+5, 22)==0) ) {
+		client_myds->DSS=STATE_QUERY_SENT_NET;
+		client_myds->myprot.generate_pkt_ERR(true,NULL,NULL,1,1047,(char *)"HY000",(char *)"Unsupported 'LOAD DATA LOCAL INFILE' command",true);
+		client_myds->DSS=STATE_SLEEP;
+		status=WAITING_CLIENT_DATA;
+		if (mirror==false) {
+			RequestEnd(NULL);
+		}
+		l_free(pkt->size,pkt->ptr);
+		return true;
+	}
+
 	return false;
 }