WARNING: Version 5.0 of Elasticsearch has passed its EOL date.
This documentation is no longer being maintained and may be removed. If you are running this version, we strongly advise you to upgrade. For the latest information, see the current release documentation.
Synonym Token Filter
editSynonym Token Filter
editThe synonym
token filter allows to easily handle synonyms during the
analysis process. Synonyms are configured using a configuration file.
Here is an example:
{ "index" : { "analysis" : { "analyzer" : { "synonym" : { "tokenizer" : "whitespace", "filter" : ["synonym"] } }, "filter" : { "synonym" : { "type" : "synonym", "synonyms_path" : "analysis/synonym.txt" } } } } }
The above configures a synonym
filter, with a path of
analysis/synonym.txt
(relative to the config
location). The
synonym
analyzer is then configured with the filter. Additional
settings are: ignore_case
(defaults to false
), and expand
(defaults to true
).
The tokenizer
parameter controls the tokenizers that will be used to
tokenize the synonym, and defaults to the whitespace
tokenizer.
Two synonym formats are supported: Solr, WordNet.
Solr synonyms
editThe following is a sample format of the file:
# Blank lines and lines starting with pound are comments. # Explicit mappings match any token sequence on the LHS of "=>" # and replace with all alternatives on the RHS. These types of mappings # ignore the expand parameter in the schema. # Examples: i-pod, i pod => ipod, sea biscuit, sea biscit => seabiscuit # Equivalent synonyms may be separated with commas and give # no explicit mapping. In this case the mapping behavior will # be taken from the expand parameter in the schema. This allows # the same synonym file to be used in different synonym handling strategies. # Examples: ipod, i-pod, i pod foozball , foosball universe , cosmos # If expand==true, "ipod, i-pod, i pod" is equivalent # to the explicit mapping: ipod, i-pod, i pod => ipod, i-pod, i pod # If expand==false, "ipod, i-pod, i pod" is equivalent # to the explicit mapping: ipod, i-pod, i pod => ipod # Multiple synonym mapping entries are merged. foo => foo bar foo => baz # is equivalent to foo => foo bar, baz
You can also define synonyms for the filter directly in the
configuration file (note use of synonyms
instead of synonyms_path
):
{ "filter" : { "synonym" : { "type" : "synonym", "synonyms" : [ "i-pod, i pod => ipod", "universe, cosmos" ] } } }
However, it is recommended to define large synonyms set in a file using
synonyms_path
, because specifying them inline increases cluster size unnecessarily.
WordNet synonyms
editSynonyms based on WordNet format can be
declared using format
:
{ "filter" : { "synonym" : { "type" : "synonym", "format" : "wordnet", "synonyms" : [ "s(100000001,1,'abstain',v,1,0).", "s(100000001,2,'refrain',v,1,0).", "s(100000001,3,'desist',v,1,0)." ] } } }
Using synonyms_path
to define WordNet synonyms in a file is supported
as well.