Lucene doesn't support prefix search.
We have created some issues with following titles:
these words also occur in attached commented and file attachments with java source code
In our projects we need to search for the word "ComboBox" or "Box" or just "box", but it does not retrieve the issues mentioned above.
Is it possible to extend JIRA search capabiltiy with a simple search plugin, which returns results like String's indexOf ? Of course, this will result in neg. performance issues.
But I think, this way of searching is practical for us, when searching for more abstract words / partialparts of words in jira/confluence.
We use lucene as for our search engine. I did some research and it looks like Lucene starting at version 2.1 does support leading wild cards. You can see here via Apache's FAQ. We don't currently use this function. As you can see even Apache mentions it's an expensive operation.
We recommend Script Runner a third party add on (Add is no longer free) . Script Runner really beefs up JQL as you can use regex with script runner.
See more on IssueFieldMatch here.