Make _all's analyzer to not_analyzed

I'm trying to run a regexp query on the _all field, this query is failing because _all is analyzed.
Is there a way to make the _all field not analyzed?

Thanks.

Use copy_to feature instead and copy the content you want to whatever field.
This field can be non analyzed or a keyword.

Hey David, thanks for the quick reply

I cant quite figure out how to use the copy_to feature because I intend to copy a field of nested type to the new field..
Any suggestions?

An example of what you tried?