You're mistaken. VFP does not support variable length index keys. As result, an index key after ALLTRIM() will be padded back to the size of the field. Adding ALLTRIM() is not required for index to be it optimazable either because it's optimaziable w/o it already.

upper(thiswhatever)) = upper(m.thiswhatever)

The bottom line, ALLTRIM() is useless in indexes at least and dangerous at worst.

>I use alltrim() on the index, which makes the index smaller and optimized when searching on allt(upper(thiswhatever))=allt(upper(m.thiswhatever))