es中的Field Mapping的index选项的介绍：

es中的Field Mapping的index选项的介绍：
The index attribute controls how the string will be indexed. It can contain one of three values:

analyzed
First analyze the string and then index it. In other words, index this field as full text.
not_analyzed
Index this field, so it is searchable, but index the value exactly as specified. Do not analyze it.
no
Don’t index this field at all. This field will not be searchable.
The default value of index for a string field is analyzed. If we want to map the field as an exact value, we need to set it to not_analyzed: