Topic: New index - productivity select vs insert

As it is known, at creation of a new index it is required to weigh productivity of readings vs updates. But something I anywhere did not meet specific approaches actually as it to do.
Therefore for an example took one table and typical  with  and supporting this  an index.
That does this index - it replaces  tables on seek.
The table of small, 150 records. In the presence of an index, there will be a following statistics:

``````select-&gt;&gt;&gt; Table ' MyTable '. Scan count 2, logical reads 15, physical reads 0...
insert-&gt;&gt;&gt; Table ' MyTable '. Scan count 0, logical reads 4, physical reads 0...``````

Without an index:

``````select-&gt;&gt;&gt; Table ' MyTable '. Scan count 2, logical reads 18, physical reads 0...
insert-&gt;&gt;&gt; Table ' MyTable '. Scan count 0, logical reads 2, physical reads 0...``````

I.e. we have such situation that   on 3 logical reads it is less, and  - on 2 it is more. I.e.  from an index in 1 logical read as a whole.
Two questions:
- I correctly understand, what when the table becomes big, hundred thousand records - that the difference (because of  in ) becomes where , after all  will be all table, and index logical reads at  increase slightly? Adjusted for an amount  vs
- So-whether it is necessary to estimate usefulness of indexes generally?

Re: New index - productivity select vs insert

hey112;
Without a ratio chtenie/zapis to do an estimation - it is senseless. If at you the data is once interposed, and then  time is read - an index very much even  server life. And if on the contrary - to the table goes  , but  from it there is time in a year (for example - the table of dens of operation of application to which always write, but read it only in the presence of any problems in application operation) the index  is not necessary.

Re: New index - productivity select vs insert

[quote =] without a ratio chtenie/zapis to do an estimation - it is senseless. If at you the data is once interposed, and then  time is read - an index very much even  server life. And if on the contrary - to the table goes  , but  from it there is time in a year (for example - the table of dens of operation of application to which always write, but read it only in the presence of any problems in application operation) the index  is not necessary.

I know, but we assume "the typical" situation where we have is considered we tell 60-80 % , and remaining  when users view the data, and sometimes them interpose/update