[DOCS] Add some documentation about the performance of `_source` usage in scripts.

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Ben McCann 2013-11-02 20:09:24 -07:00 committed by Boaz Leskes
parent c724f0de5d
commit 46edfc484a
1 changed files with 6 additions and 0 deletions

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@ -184,6 +184,12 @@ source field is loaded per doc, parsed, and then provided to the script
for evaluation. The `_source` forms the context under which the source for evaluation. The `_source` forms the context under which the source
field can be accessed, for example `_source.obj2.obj1.field3`. field can be accessed, for example `_source.obj2.obj1.field3`.
Accessing `_source` is much slower compared to using `_doc`
but the data is not loaded into memory. For a single field access `_fields` may be
faster than using `_source` due to the extra overhead of potentially parsing large documents.
However, `_source` may be faster if you access multiple fields or if the source has already been
loaded for other purposes.
[float] [float]
=== mvel Built In Functions === mvel Built In Functions