When to not use a summary index

There are several cases where summary indexes are either inappropriate or inefficient. Consider the following:

• When you need to see the original events: In most cases, summary indexes are used to store aggregate values. A summary index could be used to store a separate copy of events, but this is not usually the case. The more events you have in your summary index, the less advantage it has over the original index.
• When the possible number of categories of data is huge: For example, if you want to know the top IP addresses seen per day, it may be tempting to simply capture a count of every IP address seen. This can still be a huge amount of data, and may not save you a lot of search time, if any. Likewise, simply storing the top 10 addresses per slice of time may not give an accurate picture over a long period of time. We will discuss this scenario under the Calculating top for a large time frame section.
• When it is impractical to slice the data across sufficient...