Understanding Search - Implementing Splunk: Big Data Reporting and Development for Operational Intelligence - page 25

Understanding Search
To successfully use Splunk, it is vital that you write effective searches. Using
the index efficiently will make your initial discoveries faster, and the reports
you create will run faster for you and others. In this chapter, we will cover:
• How to write effective searches
• How to search using fields
• Understanding time
• Saving and sharing searches
Using search terms effectively
The key to creating an effective search is to take advantage of the index. Splunk's
index is effectively a huge word index, sliced by time. The single most important
factor for the performance of your searches is how many events are
pulled from disk. The following few key points should be committed to memory:
• Search terms are case insensitive : Searches for error , Error , ERROR ,
and ErRoR are all the same thing.
• Search terms are additive : Given the search item mary error , only events
that contain both words will be found. There are Boolean and grouping
operators to change this behavior; we will discuss these later.
• Only the time frame specified is queried : This may seem obvious, but it's
a big difference from a database, which would always have a single index
across all events in a table. Since each index is sliced into new buckets over
time, only the buckets that contain events for the time frame in question
need to be queried.
• Search terms are words, not parts of words : A search for foo will not
match foobar .