mapping中index_options和term_vector的区别Elasticsearch | 作者 jingkyks | 发布于2015年04月17日 | 阅读数：10320
jingkyks - 水果铅笔2B橡皮
first of all index_options & term_vectors are two totally different things.
index_options are "options" for the index you are searching on, a
datastructure that holds "terms" to document lists (posting lists).
TermVectors are a datastructure that gives you the "terms" for a given
document and in addition their position in the document as well as their
start and end character offsets. Now the index (each field has such an
index) holds a sorted list of terms and each term points to a posting list.
these posting lists are a list of documents that contain the term. On the
posting list you can also store information like frequencies (how often did
term Y occur in document X -> useful for scoring) as well as "positions"
(at which position did term Y occur in document X -> this is required fo
phrase & span queries).
if you have for instance a field that you only use for filtering you don't
need freqs and postions so documents only will do the job. In an index the
position information is the biggest piece of data usually aside stored
fields. If you don't do phrase queries or spans you don't need them at all
so safe the disk space and improve perf by only use docs and freqs. In
previous version it wasn't possible to have only freqs but no positions
(index_options supersede omit_term_frequencies_and_positions) so this is an
improvement overall since the most common usecase might only need freqs but
jingkyks - 水果铅笔2B橡皮
TermVector.YES: Only store number of occurrences.
TermVector.WITH_POSITIONS: Store number of occurrence and positions of terms, but no offset.
TermVector.WITH_OFFSETS: Store number of occurrence and offsets of terms, but no positions.
TermVector.WITH_POSITIONS_OFFSETS:number of occurrence and positions , offsets of terms.
TermVector.NO:Don't store any term vector information.
Allows to set the indexing options, possible values are docs (only doc numbers are indexed), freqs (doc numbers and term frequencies), and positions (doc numbers, term frequencies and positions). Defaults to positions for analyzed fields, and to docs for not_analyzed fields. It is also possible to set it to offsets (doc numbers, term frequencies, positions and offsets).