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Hui 辉 ("shine" in Chinese) is a Solr client and library for Elixir.



Hui enables Solr querying, updating and other forms of interaction in Elixir or Phoenix applications.


Example - searching

  import Hui

  # query structs
  alias Hui.Query.{Standard,DisMax,Common,Facet,FacetRange,Suggest,MoreLikeThis,Highlight}

  url = "http://localhost:8983/solr/gettingstarted/select"
  search(url, [%Standard{q: "author:I*"}, %Facet{field: ["cat", "author_str"], mincount: 1}])

  suggester_url = "http://localhost:8983/solr/collection/suggest"
  suggest_query = %Suggest{q: "ha", count: 10, dictionary: ["name_infix", "ln_prefix", "fn_prefix"]}
  suggest(suggester_url, suggest_query)

  # DisMax SolrCloud query
  x = %DisMax{q: "market", qf: "description^2.3 title", mm: "2<-25% 9<-3", pf: "title", ps: 1, qs: 3}
  y = %Common{collection: "library,commons", rows: 10, distrib: true, "shards.tolerant": true, "": true}
  z = %Facet{field: ["cat", "author_str"], mincount: 1}
  search(url, [x, y, z])

  # more elaborated faceting query
  range1 = %FacetRange{range: "price", start: 0, end: 100, gap: 10, per_field: true}
  range2 = %FacetRange{range: "popularity", start: 0, end: 5, gap: 1, per_field: true}
  z = %Facet{field: ["cat", "author_str"], mincount: 1, range: [range1, range2]}
  search(url, [x, y, z])

  # the above spawns a request with the following query string
  # q=...&
  # f.price.facet.range.end=100&
  # f.price.facet.range.start=0&
  # f.popularity.facet.range.end=5&
  # facet.range=popularity&
  # f.popularity.facet.range.start=0

  # convenience functions
  suggest(suggester_url, "ha", 5, ["name_infix", "ln_prefix", "fn_prefix"], "1939")

Query parameters could be any arbitrary keywords such as [q: "*", rows: 10] or built-in query structs that provide a structured way for using the comprehensive and powerful features of Solr.

See the API reference and Solr reference guide for more details on available search parameters.


Example - updating

To add, update and delete Solr documents, as well as optimised search indexes:

  import Hui

  # Specify an update handler endpoint for JSON-formatted update
  headers = [{"content-type", "application/json"}]
  url = {"http://localhost:8983/solr/collection/update", headers}

  # Solr documents
  doc1 = %{
    "actors" => ["Ingrid Bergman", "Liv Ullmann", "Lena Nyman", "Halvar Björk"],
    "desc" => "A married daughter who longs for her mother's love is visited by the latter, a successful concert pianist.",
    "directed_by" => ["Ingmar Bergman"],
    "genre" => ["Drama", "Music"],
    "id" => "tt0077711",
    "initial_release_date" => "1978-10-08",
    "name" => "Autumn Sonata"
  doc2 = %{
    "actors" => ["Bibi Andersson", "Liv Ullmann", "Margaretha Krook"],
    "desc" => "A nurse is put in charge of a mute actress and finds that their personas are melding together.",
    "directed_by" => ["Ingmar Bergman"],
    "genre" => ["Drama", "Thriller"],
    "id" => "tt0060827",
    "initial_release_date" => "1967-09-21",
    "name" => "Persona"

  # Add the docs and commit them to the index immediately
  update(url, [doc1, doc2])

  # Send documents to another pre-configured endpoint
  update(:updater, [doc1, doc2])

  delete_by_id(url, "tt0077711") # delete one doc
  delete_by_id(url, ["tt0077711", "tt0060827"]) # delete a list of docs
  delete_by_query(url, ["genre:Drama", "name:Persona"]) # delete via filter queries

Advanced update commands may be issued using the Hui.Query.Update struct, as well as through any valid binary data encapsulating Solr documents and commands.

  import Hui
  alias Hui.Query.Update

  x = %Update{doc: [doc1, doc2], commit: true, waitSearcher: true}
  update(url, x)

  # Commits docs within 5 seconds
  x = %Update{doc: [doc1, doc2], commitWithin: 5000, overwrite: true}
  update(url, x)

  # Commit and optimise index
  update(url, %Update{commit: true, waitSearcher: true, optimize: true, maxSegments: 10})

  # Binary mode, e.g. delete a document via XML binary
  {url: "http://localhost:8983/solr/collection", [{"content-type", "application/xml"}]}
  |> update("<delete><id>9780141981727</id></delete>")

See Solr reference for more details on update commands, data types and formats.


Parsed Solr response

Solr results is returned encapsulated in the HTTP response struct containing the Solr response.

    body: "...[Solr response]..",
    headers: [
      {"Content-Type", "application/json;charset=utf-8"},
      {"Content-Length", "4005"}
    method: :get,
    options: [],
    status: 200,
    url: "http://localhost:8983/solr/gettingstarted/select?q=%2A"

JSON response is automatically parsed and decoded as map. It is accessible via the body key.

  {:ok, resp} =

  # getting a list of Solr documents (Map)
  solr_docs = resp.body["response"]["docs"]
  total_hits = resp.body["response"]["numFound"]

Note: other response formats such as XML, are currently being returned as raw text.


HTTP clients and endpoints settings

Solr endpoints and request handlers may be specified in multiple ways:

  # binary string endpoint"http://localhost:8983/solr/collection/select", q: "loch")

  # atomic key referring to an endpoint in configuration - see "Configuration", q: "edinburgh", rows: 10)

  # a tuple containing HTTP headers and client options
  headers = [{"accept", "application/json"}]
  options = [timeout: 10000]
  url = {"http://localhost:8983/solr/collection/suggest", headers, options}, %Hui.Query.Suggest{q: "el", dictionary: "mySuggester"})

HTTP headers and client options for a specific endpoint may also be included in the a {url, headers, options} tuple where:

If HTTPoison is used, advanced HTTP options such as the use of connection pools may also be specified via options, e.g. [hackney: [pool: :default]]


Deploying an HTTP client

Hui relies on an existing client to facilitate HTTP requests. It currently provides support for the following clients:

Instead of using the default httpc client, one of the above HTTP clients may be deployed by adding the client as dependency and specificying it via the http_client configuration - see below. Other HTTP clients may also be used by implementing the Hui.Http.Client behaviour.

  config :hui,
    http_client: Hui.Http.Clients.Finch
  defp deps do
      {:finch, "~> 0.16"}

For Finch (only), you also need to start it from your supervision tree and configure it as below:

  # use the same name specified in the supervision tree
  config :hui, :finch, name: FinchSolr

See Hui.Http.Client for further details.



Hui is available in Hex, the package can be installed by adding hui to your list of dependencies in mix.exs:

  def deps do
      {:hui, "~> 0.11.0"}

Then run $ mix deps.get.

Documentation can be found at



A default Solr endpoint may be specified in the application configuration. HTTP headers and options may also be configured.

  config :hui, :default,
    url: "http://localhost:8983/solr/gettingstarted/select",
    headers: [{"accept", "application/json"}]
    options: [timeout: 10_000]

The URL endpoint should also include various request handlers for many purposes (search, autosuggest, spellcheck, indexing etc.). The handlers are configured in different custom or normative names in Solr configuration, e.g. "select" for search queries.

Additional endpoints and request handlers can be configured in Hui using arbitrary config keys (e.g. :suggester):

  config :hui, :suggester,
    url: "http://localhost:8983/solr/collection/suggest"

Use the config key to represent Solr endpoints in functions such as


Software library

Hui modules and data structures can be used for building Solr application in Elixir and Phoenix. The query struct modules provide idiomatic and structured ways for creating and encoding Solr parameters. For example, multiple filters and facet fields can be specified via list. fq: ["field1", "field2"], field: ["field1", "field2"], gap: 10 Elixir codes.

"Per-field" faceting can be specified in a succinct and unified way, e.g. gap instead of the long-winded f.[fieldname] (per field) or (single field). Per-field usage for a particular facet can be set or unset via the per_field key (example below).

Hui.Encoder protocol and Hui.Encode utility provide support for encoding query structs into binary and IO data formats. A custom query struct may be developed by implementing the Encoder protocol.

  alias Hui.Query.{Facet,FacetRange}

  %Facet{field: ["type", "year", "subject"], query: "edited:true"}
  |> Hui.Encoder.encode
  # -> "facet=true&facet.field=type&facet.field=year&facet.field=subject&facet.query=edited%3Atrue"
  # facet=true, facet prefixes are generated implicitly

  # a unified way to specify per-field or singe-field faceting
  x = %FacetRange{range: "age", gap: 10, start: 0, end: 100}
  x |> Hui.Encoder.encode
  # -> "facet.range.end=100&"

 %{x | per_field: true} # toggle per field faceting
  |> Hui.Encoder.encode
  # -> "f.age.facet.range.end=100&"

Hui.Query.Update struct enables various JSON-formatted update and grouped commands to be generated.

  alias Hui.Query.Update
  alias Hui.Encoder

  # doc1, doc2 are Maps of Solr documents
  x = %Update{doc: [doc1, doc2], commit: true, commitWithin: 1000}
  x |> Encoder.encode
  # -> "{\"add\":{\"commitWithin\":1000,\"doc\":{...}},\"add\":{\"commitWithin\":1000,\"doc\":{...}},\"commit\":{}}"

  # Delete the documents by ID
  %Update{delete_id: ["tt1316540", "tt1650453"]} |> Encoder.encode
  # -> "{\"delete\":{\"id\":\"tt1316540\"},\"delete\":{\"id\":\"tt1650453\"}}"

The structs and their associated type spec also provide binding to and introspection of available Solr parameters.

  iex> %Hui.Query.Facet{field: ["type", "year"], query: "year:[2000 TO NOW]"}
    contains: nil,
    "contains.ignoreCase": nil,
    "enum.cache.minDf": nil,
    excludeTerms: nil,
    exists: nil,
    facet: true,
    field: ["type", "year"],
    interval: nil,
    limit: nil,
    matches: nil,
    method: nil,
    mincount: nil,
    missing: nil,
    offset: nil,
    "overrequest.count": nil,
    "overrequest.ratio": nil,
    pivot: [],
    "pivot.mincount": nil,
    prefix: nil,
    query: "year:[2000 TO NOW]",
    range: nil,
    sort: nil,
    threads: nil


IO data encoding

To leverage Erlang runtime and some HTTP client features for lower memory usage and increased performance, Hui.Encoder provides functions to return either string or IO data which can be sent directly to IO functions or over the socket.

Copyright (c) 2023 Boon Low

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.