[[search-request-sort]] === Sort Allows to add one or more sort on specific fields. Each sort can be reversed as well. The sort is defined on a per field level, with special field name for `_score` to sort by score, and `_doc` to sort by index order. Assuming the following index mapping: [source,js] -------------------------------------------------- PUT /my_index { "mappings": { "my_type": { "properties": { "post_date": { "type": "date" }, "user": { "type": "keyword" }, "name": { "type": "keyword" }, "age": { "type": "integer" } } } } } -------------------------------------------------- // CONSOLE [source,js] -------------------------------------------------- GET /my_index/my_type/_search { "sort" : [ { "post_date" : {"order" : "asc"}}, "user", { "name" : "desc" }, { "age" : "desc" }, "_score" ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE // TEST[continued] NOTE: `_doc` has no real use-case besides being the most efficient sort order. So if you don't care about the order in which documents are returned, then you should sort by `_doc`. This especially helps when <>. ==== Sort Values The sort values for each document returned are also returned as part of the response. ==== Sort Order The `order` option can have the following values: [horizontal] `asc`:: Sort in ascending order `desc`:: Sort in descending order The order defaults to `desc` when sorting on the `_score`, and defaults to `asc` when sorting on anything else. ==== Sort mode option Elasticsearch supports sorting by array or multi-valued fields. The `mode` option controls what array value is picked for sorting the document it belongs to. The `mode` option can have the following values: [horizontal] `min`:: Pick the lowest value. `max`:: Pick the highest value. `sum`:: Use the sum of all values as sort value. Only applicable for number based array fields. `avg`:: Use the average of all values as sort value. Only applicable for number based array fields. `median`:: Use the median of all values as sort value. Only applicable for number based array fields. ===== Sort mode example usage In the example below the field price has multiple prices per document. In this case the result hits will be sorted by price ascending based on the average price per document. [source,js] -------------------------------------------------- PUT /my_index/my_type/1?refresh { "product": "chocolate", "price": [20, 4] } POST /_search { "query" : { "term" : { "product" : "chocolate" } }, "sort" : [ {"price" : {"order" : "asc", "mode" : "avg"}} ] } -------------------------------------------------- // CONSOLE [[nested-sorting]] ==== Sorting within nested objects. Elasticsearch also supports sorting by fields that are inside one or more nested objects. The sorting by nested field support has the following parameters on top of the already existing sort options: `nested_path`:: Defines on which nested object to sort. The actual sort field must be a direct field inside this nested object. When sorting by nested field, this field is mandatory. `nested_filter`:: A filter that the inner objects inside the nested path should match with in order for its field values to be taken into account by sorting. Common case is to repeat the query / filter inside the nested filter or query. By default no `nested_filter` is active. ===== Nested sorting example In the below example `offer` is a field of type `nested`. The `nested_path` needs to be specified; otherwise, elasticsearch doesn't know on what nested level sort values need to be captured. [source,js] -------------------------------------------------- POST /_search { "query" : { "term" : { "product" : "chocolate" } }, "sort" : [ { "offer.price" : { "mode" : "avg", "order" : "asc", "nested_path" : "offer", "nested_filter" : { "term" : { "offer.color" : "blue" } } } } ] } -------------------------------------------------- // CONSOLE Nested sorting is also supported when sorting by scripts and sorting by geo distance. ==== Missing Values The `missing` parameter specifies how docs which are missing the field should be treated: The `missing` value can be set to `_last`, `_first`, or a custom value (that will be used for missing docs as the sort value). For example: [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "price" : {"missing" : "_last"} } ], "query" : { "term" : { "product" : "chocolate" } } } -------------------------------------------------- // CONSOLE NOTE: If a nested inner object doesn't match with the `nested_filter` then a missing value is used. ==== Ignoring Unmapped Fields By default, the search request will fail if there is no mapping associated with a field. The `unmapped_type` option allows to ignore fields that have no mapping and not sort by them. The value of this parameter is used to determine what sort values to emit. Here is an example of how it can be used: [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "price" : {"unmapped_type" : "long"} } ], "query" : { "term" : { "product" : "chocolate" } } } -------------------------------------------------- // CONSOLE If any of the indices that are queried doesn't have a mapping for `price` then Elasticsearch will handle it as if there was a mapping of type `long`, with all documents in this index having no value for this field. [[geo-sorting]] ==== Geo Distance Sorting Allow to sort by `_geo_distance`. Here is an example, assuming `pin.location` is a field of type `geo_point`: [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "_geo_distance" : { "pin.location" : [-70, 40], "order" : "asc", "unit" : "km", "mode" : "min", "distance_type" : "sloppy_arc" } } ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE `distance_type`:: How to compute the distance. Can either be `sloppy_arc` (default), `arc` (slightly more precise but significantly slower) or `plane` (faster, but inaccurate on long distances and close to the poles). `mode`:: What to do in case a field has several geo points. By default, the shortest distance is taken into account when sorting in ascending order and the longest distance when sorting in descending order. Supported values are `min`, `max`, `median` and `avg`. `unit`:: The unit to use when computing sort values. The default is `m` (meters). NOTE: geo distance sorting does not support configurable missing values: the distance will always be considered equal to +Infinity+ when a document does not have values for the field that is used for distance computation. The following formats are supported in providing the coordinates: ===== Lat Lon as Properties [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "_geo_distance" : { "pin.location" : { "lat" : 40, "lon" : -70 }, "order" : "asc", "unit" : "km" } } ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE ===== Lat Lon as String Format in `lat,lon`. [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "_geo_distance" : { "pin.location" : "40,-70", "order" : "asc", "unit" : "km" } } ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE ===== Geohash [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "_geo_distance" : { "pin.location" : "drm3btev3e86", "order" : "asc", "unit" : "km" } } ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE ===== Lat Lon as Array Format in `[lon, lat]`, note, the order of lon/lat here in order to conform with http://geojson.org/[GeoJSON]. [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "_geo_distance" : { "pin.location" : [-70, 40], "order" : "asc", "unit" : "km" } } ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE ==== Multiple reference points Multiple geo points can be passed as an array containing any `geo_point` format, for example [source,js] -------------------------------------------------- GET /_search { "sort" : [ { "_geo_distance" : { "pin.location" : [[-70, 40], [-71, 42]], "order" : "asc", "unit" : "km" } } ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE and so forth. The final distance for a document will then be `min`/`max`/`avg` (defined via `mode`) distance of all points contained in the document to all points given in the sort request. ==== Script Based Sorting Allow to sort based on custom scripts, here is an example: [source,js] -------------------------------------------------- GET /_search { "query" : { "term" : { "user" : "kimchy" } }, "sort" : { "_script" : { "type" : "number", "script" : { "lang": "painless", "inline": "doc['field_name'].value * params.factor", "params" : { "factor" : 1.1 } }, "order" : "asc" } } } -------------------------------------------------- // CONSOLE ==== Track Scores When sorting on a field, scores are not computed. By setting `track_scores` to true, scores will still be computed and tracked. [source,js] -------------------------------------------------- GET /_search { "track_scores": true, "sort" : [ { "post_date" : {"order" : "desc"} }, { "name" : "desc" }, { "age" : "desc" } ], "query" : { "term" : { "user" : "kimchy" } } } -------------------------------------------------- // CONSOLE ==== Memory Considerations When sorting, the relevant sorted field values are loaded into memory. This means that per shard, there should be enough memory to contain them. For string based types, the field sorted on should not be analyzed / tokenized. For numeric types, if possible, it is recommended to explicitly set the type to narrower types (like `short`, `integer` and `float`).