Elasticsearch text phrase prefix search with expansion

elastic_text_phrase_search

From Docs: max_expansions parameter that can control to how many prefixes the last term will be expanded. It is highly recommended to set it to an acceptable value to control the execution time of the query.

curl -X DELETE localhost:9200/cities
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Gabriel" }' 
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Gwann" }' 
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Carlos" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Cristobal" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Clemente" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Diego" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Dimas" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Douglas" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Francisco" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Felipe" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Francisco De Dos Rios" }'
curl -X POST "http://localhost:9200/cities/city" -d '{ "city" : "San Fidel" }'

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curl -XGET 'http://localhost:9200/cities/_search?pretty=true' -d '
{
  "query" : {
    "text_phrase_prefix" : {
        "city" : {
            "query" : "San f",
            "max_expansions" : 0
        }
    }
  }
}'

{
  "took" : 33,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : 1.3646637,
    "hits" : [ {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "461gnzgbQX-RzCyrOFlEgQ",
      "_score" : 1.3646637, "_source" : { "city" : "San Francisco De Dos Rios" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "-Sw_PeYJQg2nlyVpJYknvA",
      "_score" : 1.3236144, "_source" : { "city" : "San Felipe" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "rvN_BPllQie-xL-xtkHA0g",
      "_score" : 0.9965843, "_source" : { "city" : "San Francisco" }
    } ]
  }

3 hits, San Fidel not returned, not sure why

----------------------------------------------------------------------------------------------

curl -XGET 'http://localhost:9200/cities/_search?pretty=true' -d '
{
  "query" : {
    "text_phrase_prefix" : {
        "city" : {
            "query" : "San f",
            "max_expansions" : 2
        }
    }
  }
}'

{
  "took" : 43,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 4,
    "max_score" : 2.2020302,
    "hits" : [ {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "-Sw_PeYJQg2nlyVpJYknvA",
      "_score" : 2.2020302, "_source" : { "city" : "San Felipe" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "WMbYShc5TWa-TjQ0rjL5Vg",
      "_score" : 2.2020302, "_source" : { "city" : "San Fidel" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "461gnzgbQX-RzCyrOFlEgQ",
      "_score" : 1.3646637, "_source" : { "city" : "San Francisco De Dos Rios" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "rvN_BPllQie-xL-xtkHA0g",
      "_score" : 0.9965843, "_source" : { "city" : "San Francisco" }
    } ]
  }

4 hits returned

----------------------------------------------------------------------------------------------

curl -XGET 'http://localhost:9200/cities/_search?pretty=true' -d '
{
  "query" : {
    "text_phrase_prefix" : {
        "city" : {
            "query" : "San d",
            "max_expansions" : 0
        }
    }
  }
}'

{
  "took" : 2,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 0,
    "max_score" : null,
    "hits" : [ ]
  }

0 returned, should this be?

----------------------------------------------------------------------------------------------

curl -XGET 'http://localhost:9200/cities/_search?pretty=true' -d '
{
  "query" : {
    "text_phrase_prefix" : {
        "city" : {
            "query" : "San d",
            "max_expansions" : 2
        }
    }
  }
}'

{
  "took" : 22,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 1,
    "max_score" : 3.3574967,
    "hits" : [ {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "DpbmhNrTRWyPQZlNkDL-_A",
      "_score" : 3.3574967, "_source" : { "city" : "San Diego" }
    } ]
  }

1 hit?

----------------------------------------------------------------------------------------------

curl -XGET 'http://localhost:9200/cities/_search?pretty=true' -d '
{
  "query" : {
    "text_phrase_prefix" : {
        "city" : {
            "query" : "San d",
            "max_expansions" : 3
        }
    }
  }
}'

{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 2,
    "max_score" : 4.7654734,
    "hits" : [ {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "DpbmhNrTRWyPQZlNkDL-_A",
      "_score" : 4.7654734, "_source" : { "city" : "San Diego" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "ahHdrzDhTbSad_qShrbN7g",
      "_score" : 4.7654734, "_source" : { "city" : "San Dimas" }
    } ]
  }

----------------------------------------------------------------------------------------------

curl -XGET 'http://localhost:9200/cities/_search?pretty=true' -d '
{
  "query" : {
    "text_phrase_prefix" : {
        "city" : {
            "query" : "San d",
            "max_expansions" : 5
        }
    }
  }
}'

{
  "took" : 20,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : 7.581427,
    "hits" : [ {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "DpbmhNrTRWyPQZlNkDL-_A",
      "_score" : 7.581427, "_source" : { "city" : "San Diego" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "ahHdrzDhTbSad_qShrbN7g",
      "_score" : 7.581427, "_source" : { "city" : "San Dimas" }
    }, {
      "_index" : "cities",
      "_type" : "city",
      "_id" : "_hEbRStmSIeI407ev9txeg",
      "_score" : 7.581427, "_source" : { "city" : "San Douglas" }
    } ]
  }

how much the value of number_of_shards is setting to?