WARNING: Version 5.2 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.

« Phonetic Token Filter Synonym Graph Token Filter »

› › ›

Synonym Token Filter

edit

Synonym Token Filter

edit

The 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

edit

The 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

edit

Synonyms 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.

« Phonetic Token Filter Synonym Graph Token Filter »