What’s in Search Crawl SQL database anyway?
Inside are information about status, time etc. found by crawling.
average size for crawl = 0,046 * (content SQL DB)
How to reduce size of Crawl Search SQL DB?
From SharePoint 2010 we can use Health Analyzer for reducing big sized Crawl Search DB. If you for any reason stop crawling scheduled job or remove crawled content then sometimes indexing generates too big search database.
Or it might be fragmented indices. In this case just found rule Search in Health Analyzer and set the rule, that will automatically defrag if many fragmented indices are found.
Search Crawl database often have plenty of empty space. If with defragmentation we didn’t get wanted result, than you can restore crawl db in 2 different ways.
In SharePoint admin console:
Central Administration found Search Administration
Stop All Crawl in content Sources
In Index reset undo Deactivate search alerts during reset in click on Reset Now
In SQL server:
Found Search DB Crawl and open All Tasks – Shrink – Database: undo Reorganize files before releasing unused space
Again for All Tasks – Shrink – Files: undo Release unused space files before releasing unused space