About indexed field extraction
When Splunk indexes data, it parses the data stream into a series of events. As part of this process, it adds a number of fields to the event data. These fields include default fields that it adds automatically and any custom fields that you specify.
The process of adding fields to events is known as field extraction. There are two types of field extraction:
- Indexed field extraction, which was described briefly at the start of this topic and which forms the basis for this chapter. These fields are stored in the index and become part of the event data.
- Search-time field extraction, which takes place when data is searched. Those fields are created on the fly and are not stored in the index. See "Create search-time field extractions" in the Knowledge Manager manual for information about this type of field extraction.
There are three types of indexed fields:
- Default fields, which Splunk automatically adds to each event. See "About default fields" in this chapter.
- Custom fields, which you specify. See "Create custom fields at index-time" in this chapter.
- File header fields. Splunk can extract fields automatically from the headers of CSV files. See "Extract fields from file headers" in this chapter.
Important: It's usually a bad idea to create custom fields at index-time. You can, on the other hand, create all the custom fields you want at search-time. For details, read "Create custom fields at index-time".
Tune timestamp recognition for better indexing performance
About default fields (host, source, sourcetype, and more)
This documentation applies to the following versions of Splunk® Enterprise: 4.3, 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5, 4.3.6, 4.3.7