从在弹性搜索上使用正则表达式过滤器开始的正则表达式是什么？

Question

I'm working on a Search Engine using Elastic Search - I'm using its java API. And would like to configure a regexp filter for my queries particularly a "starts with" filter.

Suppose I have these titles in my Index:

1. the world
2. things about him
3. george's ultimatum
4. jumping
5. jimmy and the flock

If I would like to get the results exactly starting with the letter t or th, what regular expression should I use?

CORRECT RESULTS AFTER SEARCH SHOULD BE

1. the world
2. things about him

I've tried using:

^t.*   OR   ^[t.*]

But doesn't return any results. The starting anchor ^ doesn't work on Elastic even though the documentation says so.

t.*   OR   [t.*]

But it works just like the prefix filter, and includes the result "jimmy and the flock"

Note:

• I cannot use the regexp query (A limitation of the search engine I'm building) so I'm forced to use only a filter
• I've tried using the prefix filter but it will evaluate terms, using the prefix parameter "t" for example will include the title "jimmy and the flock" because of "the" term

BTW, I'm using ES version 1.0.0

Answer 1

There is a special page on the ElasticSearch blog that exactly answers your problem: http://www.elasticsearch.org/blog/starts-with-phrase-matching/ ; as pickypg suggests, it is a mapping problem, you must set a special analyzer that combines the "keyword" tokenizer and the "lowercase" filter.