如何在弹性搜索中比较两个文本字段

Question

I have a need to compare two text fields in elastic search, but they are text fields. For normal fields I can use script to compare using doc['field'].value, but is there a way to do the same for text fields.

Answer 1

See below excerpt from ES DOCS :

By far the fastest most efficient way to access a field value from a script is to use the doc['field_name'] syntax, which retrieves the field value from doc values. Doc values are a columnar field value store, enabled by default on all fields except for analyzed text fields.

There are 2 ways known to me to access a text value from script.

1. Map a keyword representation of a text field as well and access that field.

 { "mappings": { "properties": { "name":{ "type": "text", "fields": { "keyword":{ // <======= See this "type":"keyword" } } } } } }

The keyword representation can be accessed like 'doc[name.keyword].value'

It is recommended to index/store keyword representation of fields for small-size text fields like 'name', 'emailId' but is not recommended for larger fields like 'description', due to memory overhead

2. Another way is to enable field data on the text field and access that field.

Fielddata is disabled on text fields by default. Set fielddata=true on [ your_field_name ] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory.

It is not recommended to use the field-data over the text fields however.

Note: Please do add details on why you need comparison and what kind of comparison is required on 'text' fields.