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synonym (同义词)词元过滤器允许在分析过程中轻松处理同义词。 同义词使用配置文件配置。示例如下:

PUT /test_index
{
    "settings": {
        "index" : {
            "analysis" : {
                "analyzer" : {
                    "synonym" : {
                        "tokenizer" : "whitespace",
                        "filter" : ["synonym"]
                    }
                },
                "filter" : {
                    "synonym" : {
                        "type" : "synonym",
                        "synonyms_path" : "analysis/synonym.txt"
                    }
                }
            }
        }
    }
}

以上配置一个 synonym (同义词)过滤器,其中包含一个路径 analysis/synonym.txt(相对于 config 位置)。 然后使用过滤器配置 synonym  同义词分析器。 其他设置有:ignore_case(默认为 false),和 expand (默认为 true)。

tokenizer 参数控制将用于标记同义词的分词器,并且默认为 whitespace  分词器。

支持两种同义词格式:Solr,WordNet

Solr synonyms

以下是文件的示例格式:

# 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
lol, laughing out loud

# 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

您也可以在配置文件中直接给过滤器定义同义词(请注意使用 synonyms 而不是 synonyms_path ):

PUT /test_index
{
    "settings": {
        "index" : {
            "analysis" : {
                "filter" : {
                    "synonym" : {
                        "type" : "synonym",
                        "synonyms" : [
                            "i-pod, i pod => ipod",
                            "universe, cosmos"
                        ]
                    }
                }
            }
        }
    }
}

但是,建议使用 synonyms_path 在文件中定义大型同义词集,因为内联指定会不必要地增加群集大小。

WordNet synonyms

基于 WordNet 格式的 同义词 可以如下使用格式声明:

 PUT /test_index
{
    "settings": {
        "index" : {
            "analysis" : {
                "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)."
                        ]
                    }
                }
            }
        }
    }
}

同时支持使用 synonyms_path  在文本中定义 WordNet synonyms