We Keep Coding

How to translate Elastic Search query in Java by using the query builder?

I am trying to translate the following elastic search query in Java, using the query builder? Can someone give any ideas of it?
GET <index-name>/_search
{
“size”: 1,
“sort”: [
{
“Date”: {
“order”: “desc”
}
}
]
}

You need to use SortBuilder to sort on fields. Below request will sort Date field in desc order
RestHighLevelClient client = new RestHighLevelClient(restClientBuilder);
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.size(1).sort(new FieldSortBuilder("Date").order(SortOrder.DESC));
SearchRequest searchRequest = new SearchRequest("my-index");
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

Java equivalent of elasticsearch CURL query?

My project had a new reqiurement of migrating all datas which are currently in postresql to elasticsearch. Successfully migrated all my datas, but I am stuck with writing java code to search for some datas in elastic search index.
Sample structure of a hit in index is attached in the below image:
I need to find average of activity.attentionLevel from the index.
I wrote something like below query to find average:
GET proktor-activities/_search
{
"aggs" : {
"avg_attention" : {
"avg" : {
"script" : "Float.parseFloat(doc['activity.attentionLevel.keyword'].value)" }
}
}
}
please help me to find java equivalent code for doing the same.
thanks in advance

Using Elastic's RestHighLevel API would be something like this:
// Create the client
RestHighLevelClient client = new RestHighLevelClient(
RestClient.builder(new HttpHost("localhost", 9200, "http")));
// Specify the aggregation request
SearchRequest searchRequest = new SearchRequest("proktor-activities");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.aggregation(AggregationBuilders
.avg("avg_attention")
.field("activity.attentionLevel"));
searchRequest.source(searchSourceBuilder);
// Execute the aggreagation with Elasticsearch
SearchResponse response = client.search(searchRequest, RequestOptions.DEFAULT);
// Read the aggregation result
Aggregations aggregations = response.getAggregations();
Avg averageAttention = aggregations.get("avg_attention");
double result = averageAttention.getValue();
client.close(); // get done with the client
More information here.

How to use search_after in Elastic High Level Rest Client for pagination

I am using elastic RestHighLevelClient to talk to ES. I am able to query basic queries. Although i am trying to use teh search_after api to design a paginated api from my front end queries. Although query_after is simple to use in the RestLowLevelClient api, i am not able to figure how to use it in the HighLevel API.
Looks like the lucene api has SearchAfterSortedDocQuery, but i am not able to figure how to use it with the elastic search api. For example: in the code below i initialize SearchAfterSortedDocQuery query but not sure how to use it .
RestHighLevelClient client = ESRestClient.getClient();
SearchRequest searchRequest = new SearchRequest();
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.termQuery("field1",value1));
searchSourceBuilder.query(QueryBuilders.termQuery("field2",value2));
searchSourceBuilder.from(0);
searchSourceBuilder.size(limit);
SortField[] sortFields = new SortField[2];
sortFields[0]= new SortField("field1", SortField.Type.LONG);
sortFields[1]= new SortField("field2", SortField.Type.LONG);
FieldDoc fieldDoc = new FieldDoc(0,0); //Is this correct? how to initialize field doc?
fieldDoc.fields = new Object[2];
fieldDoc.fields[0] = new Long("-156034");
fieldDoc.fields[1] = new Long("2297416849");
SearchAfterSortedDocQuery query = new SearchAfterSortedDocQuery(new Sort(sortFields), fieldDoc);
searchRequest.source(searchSourceBuilder);
searchRequest.indices("index1");
try {
SearchResponse response = client.search(searchRequest, RequestOptions.DEFAULT);
System.out.println(response);
}
catch(IOException e){
System.out.println(e);
}
}

I think instead of you using SearchAfterSortedDocQuery, just set search_after in searchSourceBuilder look like below
searchSourceBuilder.searchAfter(new Object[]{sortAfterValue});
after that use SearchRequest and rest client to get the response
SearchRequest searchRequest = new SearchRequest("index");
searchRequest.types("type");
searchRequest.source(searchSourceBuilder);
SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT)
SearchHits hits = searchResponse.getHits();
final you should keep the last sort value by getSortValues() from hits to go to the next page.
hits.getAt(lastIndex).getSortValues()
Elasticsearch search_after api
hope this help.

High level rest client get only hits' size

i know with transport client can get hits' count like this:
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.action.search.SearchType;
import org.elasticsearch.index.query.QueryBuilders.*;
SearchResponse response = client.prepareSearch("your_index_goes_here")
.setTypes("YourTypeGoesHere")
.setQuery(QueryBuilders.termQuery("some_field", "some_value"))
.setSize(0) // Don't return any documents, we don't need them.
.get();
SearchHits hits = response.getHits();
long hitsCount = hits.getTotalHits();
but how can i get hits' size with high level rest client?

If you are using Elasticsearch 6.6 or newer. Maybe you want to use the Count API: https://www.elastic.co/guide/en/elasticsearch/reference/6.6/search-count.html
In high level rest client (https://www.elastic.co/guide/en/elasticsearch/client/java-rest/6.6/java-rest-high-count.html):
CountRequest countRequest = new CountRequest("your_index_goes_here");
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
searchSourceBuilder.query(QueryBuilders.termQuery("some_field", "some_value"));
countRequest.source(searchSourceBuilder);
CountResponse countResponse = client.count(countRequest, RequestOptions.DEFAULT);
long hitsCount = countResponse.getCount();

Here is a version with the REST client:
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder()
.query(queryBuilder)
.size(1);
SearchRequest searchRequest = new SearchRequest("your_index_goes_here");
searchRequest.source(searchSourceBuilder);
SearchResponse response = highLevelClient.search(searchRequest, RequestOptions.DEFAULT);
System.out.println("Total: " + response.getResponse().getHits().totalHits);

Another potential solution is to use the aggregation builder and get the count that way.
sourceBuilder.aggregation(AggregationBuilders.count("totalCount").field("id"));
As you can see you can base it on the ID or any other unique value that would give you a total count of all fields based on the query you send.

Elasticsearch MultiSearchRequestBuilder

I have written a query and want to set index on each query execution dynamically. How can I pass the index name.
MultiSearchRequestBuilder multiSearchRequestBuilder = null;
multiSearchRequestBuilder = client.prepareMultiSearch()

You need to build one SearchRequest per request you want to make on any index of your choice and then add that SearchRequest to MultiSearchRequestBuilder
SearchRequest searchRequest1 = new SearchRequest("index1");
multiSearchRequestBuilder.add(searchRequest1);
SearchRequest searchRequest2 = new SearchRequest("index2");
multiSearchRequestBuilder.add(searchRequest2);