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Individual fields can be boosted — count more towards the relevance score — at index time, with the
boost parameter as follows:
Matches on the
Note that a
title field will usually be shorter than a
content field. The
default relevance calculation takes field length into account, so a short
title field will have a higher natural boost than a long
Why index time boosting is a bad idea
We advise against using index time boosting for the following reasons:
- You cannot change index-time
boostvalues without reindexing all of your documents.
- Every query supports query-time boosting which achieves the same effect. The
difference is that you can tweak the
boostvalue without having to reindex.
- Index-time boosts are stored as part of the
norm, which is only one byte. This reduces the resolution of the field length normalization factor which can lead to lower quality relevance calculations.
The only advantage that index time boosting has is that it is copied with the
value into the
_all field. This means that, when
_all field, words that originated from the
title field will
have a higher score than words that originated in the
This functionality comes at a cost: queries on the
_all field are slower
when index-time boosting is used.