Is it wrong to create index writer on each query request.

[Rajendra Rao]

I have system in which documents and Query comes  frequently  .I am
creating index writer in memory every time for each query I request . I
want to know Is it good to separate Index Writing and loading  and Query
request ?  Whether It is good to save index writer on hard disk .Whether it
is time consuming to update index writer when new document will come.