Dave Elliott said:
For performance issues, is it a good or bad idea to index some or all
of the fields, and what is the criteria to or not to index?
In principle, it's a good idea to index those fields that will
frequently be used in query criteria or for sorting. This can make an
enormous difference in query performance, if the table is large. You
don't necessarily want to index every conceivable field, though, because
(a) the indexes themselves can take up significant storage space, and
(b) maintaining each index takes extra time whenever records are added
or deleted, or the values of their indexed fields are changed.