Lucene.net - Index Format

Directory, Document, Fields
↓
Index, Segment, Files
----------------------------------------------------------------------------
Index: Is a container for all indexing files
Segment: a sub-index, and a fully independent index/search module
File: Contains physical data

Inverted index: focus on Term,

• Field names (.fnm)
  
• Term dictionary (.tis)
• Term frequencies (.frq)
  
• Term positions (.prx)

Files:

• Per-Index Files
  • Segments File
  • Lock File
  • Deletable File
  • Compound Files
• Per-Segment Files
  • Fields
  • Term Dictionary
  • Frequencies
  • Positions
  • Normalization Factors
  • Term Vectors
  • Deleted Documents

Some definition:

• A document is a sequence of Fields;
• A Field is a named sequence of Terms;
• A Term is a string