Service Catalog issue

Hello!

Recently we have significantly increased our service catalog records. Currently we have about 8000 records. And then we faced problems with searching through ess portal. It works too slow. I have found that the function buildSearchQuery was changed in svcCatCategory library in our environment. OOB version: 

return "displayName=\""  searchStr  "\"";

was changed to:

return "index(\""  searchStr  "\", displayName)>0";

Reverting the change increases performance, but it does not return all results. I have run IR regen on svcDisplay table. But there are different number of records in scirexpert table on each regen run. Why IR regen process returning different results? And how can we return all results using OOB version code?