How to implement autocomplete and advance database queries in firebase

Why firebase?

• Quick and easy setup.
• Realtime database (No need for state management)*.
• Cloud functions support for advance business logic.
• Email/phone and all major third party auth provider support.

To maintain practical context throughout the post, let’s consider the use case where we are building a simple match making app and possible data structure can be as followed.

With Firebase as the database, we have a few limitations

• No support for compound queries
  can’t search for a match which is both female and willing to shift.
• No way to define sorting order (It’s ascending by default).
  can’t sort matches by their age from oldest to youngest.
• No way to implement autocomplete that is case insensitive or full text.
  can’t search for a match which is interested in dancing.
• Pagination implementation works only when the ordering parameter is unique
  can’t implement pagination if matches are sorted by their age.

Workarounds

Database restructuring
dividing users into male, female and all nodes, and then searching for a match willing to relocate in female node works.
Number of nodes and in turn redundancy increase as number of search parameters increase.

Firestore
We could use firestore as the database, since it supports compound queries and both sorting orders. Chained queries like

• Still no support for autocomplete.
  can’t search for a match by it’s last name or hobbies.
• Sorting and ordering by different parameter is not allowed.
  can’t sort men filtered by their age.

The solution I propose, is to use Algolia

Algolia is a hosted full-text, numerical, and faceted search engine capable of delivering realtime results from the first keystroke. Algolia’s powerful API lets you quickly and seamlessly implement search within your websites and mobile applications.

- Algolia Documentation

Few things I considered before committing to Algolia

• Although algolia is heavily marketed as full text solution, which it is, it has filtering, sorting and autocomplete capabilities as well.
• A quick google search for integrating algolia with firebase, gives complicated answers about writing cloud functions to search algolia indices and saving those results into the firebase database and the reading it from there. Algolia has client side javascript sdk with an easier integration.
• You need at least working knowledge of firebase cloud functions in order to sync firebase lists with algolia indices.
• Algolia is a paid service, free community plan just allows
  - storing of 10k records (users in our case)
  - 100k operations (counts every records creation, updates and queries).

Setup is pretty straight forward

Algolia in effort to provide relevant results, gives user lots options to customise their query. This can be overwhelming, so let’s consider only few relevant things for now.

• Search/Autocomplete
• Pagination
• Ordering (Ranking)
• Compound Queries (Filters)
• Facets

Ranking, filters and facets are words from algolia’s vocabulary. Facets and filters, in general, are used for restricting search to a subset of results. Difference between facets and filters

• Filters are used when filtering is done entirely hidden from the end user Serving curated matches for our match making app user’s preferences.
• Facets generally used for building a UI, where users can select facets (as categories) to further refine their query
  Can provide dropdown to our users to refine matches from specific cities.

Search

Search can be as simple as simple query and can be complex with filters or facets or both as well. There are lots of search parameter options along with query and all documented here.

Pagination

Filters

Filters can be used with or without query parameter.

Ranking

Custom ranking or ordering in realtime is not possible when used in client side, index.setSettings method doesn’t work with client-side apis, but we can always set default ranking type to whatever order we want from algolia’s dashboard.
Also, algolia’s dashboard gives an option to seamlessly create replicas of your index (users in our cases) with different ranking strategy.

For our matchmaking app, we can easily create a recommendation engine, using these options . The features I talked about are just the tip of the iceberg, algolia has many more powerful and advanced options. Those can be found here in algolia's documentation.