Common Questions and Issues

Depending on how you have Sphinx setup, or what database you’re using, you might come across little issues and curiosities. Here’s a few to be aware of.

Editing the generated Sphinx configuration file

In most situations, you won’t need to edit this file yourself, and can rely on Thinking Sphinx to generate it reliably.

If you do want to customise the settings, you’ll find most options are available to set via config/sphinx.yml – many are mentioned on the Advanced Sphinx Configuration page. For those that aren’t mentioned on that page, you could still try setting it, and there’s a fair chance it will work.

On the off chance that you actually do need to edit the file, make sure you’re running the thinking_sphinx:reindex task instead of the normal thinking_sphinx:index task – as the latter will always regenerate the configuration file, overwriting your customisations.

Running multiple instances of Sphinx on one machine

You can run as many Sphinx instances as you wish on one machine – but each must be bound to a different port. You can do this via the config/sphinx.yml file – just add a setting for the port for the specific environment:

  port: 9313

Other options are documented on the Advanced Sphinx Configuration page.

Viewing Result Weights

To retrieve the weights/rankings of each search result, you can enumerate through your matches using each_with_weighting:

results.each_with_weighting do |result, weight|
  # ...

However, there is currently no clean way to get the weight of a specific result without looping though the dataset.

Wildcard Searching

Sphinx can support wildcard searching (for example: Austr∗), but it is turned off by default. To enable it, you need to add two settings to your config/sphinx.yml file:

  enable_star: 1
  min_infix_len: 1
  enable_star: 1
  min_infix_len: 1
  enable_star: 1
  min_infix_len: 1

You can set the min_infix_len value to something higher if you don’t need single characters with a wildcard being matched. This may be a worthwhile fine-tuning, because the smaller the infixes are, the larger your index files become.

Don’t forget to rebuild your Sphinx indexes after making this change.

rake thinking_sphinx:rebuild

Slow Indexing

If Sphinx is taking a while to process all your records, there are a few common reasons for this happening. Firstly, make sure you have database indexes on any foreign key columns and any columns you filter or sort by.

Secondly – are you using fixtures, or are there large gaps between primary key values for your models? Sphinx isn’t set up to process disparate IDs efficiently by default – and Rails’ fixtures have randomly generated IDs, which are usually extremely large integers. To get around this, you’ll need to set sql_range_step in your config/sphinx.yml file for the appropriate environments:

  sql_range_step: 10000000

MySQL and Large Fields

If you’ve got a field that is built off multiple values in one column – ie: through a has_many association – then you may hit MySQL’s default limit for string concatenation: 1024 characters. You can increase the group_concat_max_len value by adding the following to your define_index block:

define_index do
  # ...

  set_property :group_concat_max_len => 8192

If these fields get particularly large though, then there’s another setting you may need to set in your MySQL configuration: max_allowed_packet, which has a default of sixteen megabytes. You can’t set this option via Thinking Sphinx though (it’s a rare edge case).

PostgreSQL with Manual Fields and Attributes

If you’re using fields or attributes defined by strings (raw SQL), then the columns used in them aren’t automatically included in the GROUP BY clause of the generated SQL statement. To make sure the query is valid, you will need to explicitly add these columns to the GROUP BY clause.

A common example is if you’re converting latitude and longitude columns from degrees to radians via SQL.

define_index do
  # ...

  has "RADIANS(latitude)",  :as => :latitude,  :type => :float
  has "RADIANS(longitude)", :as => :longitude, :type => :float

  group_by "latitude", "longitude"

Delta Indexing Not Working

Often people find delta indexing isn’t working on their production server. Sometimes, this is because Sphinx is running as one user on the system, and the Rails/Merb application is being served as a different user. Check your production.log and Apache/Nginx error log file for mentions of permissions issues to confirm this.

Indexing for deltas is invoked by the web user, and so needs to have access to the index files. The simplest way to ensure this is run all Thinking Sphinx rake tasks by that web user.

If you’re still having issues, and you’re using Passenger, read the next hint.

Running Delta Indexing with Passenger

If you’re using Phusion Passenger on your production server, with delta indexing on some models, a common issue people find is that their delta indexes don’t get processed.

If it’s not a permissions issue (see the previous hint), another common cause is because Passenger has it’s own PATH set up, and can’t execute the Sphinx binaries (indexer and searchd) implicitly.

The way around this is to find out where your binaries are on the server:

which searchd

And then set the bin_path option in your config/sphinx.yml file for the production environment:

  bin_path: '/usr/local/bin'

Can only access the first thousand search results

This is actually how Sphinx is supposed to behave. Have a read of the Large Result Sets section of the Advanced Configuration page to see why, and how to work around it if you really need to.

Vendored Delayed Job, AfterCommit and Riddle

If you’ve still got Delayed Job vendored as part of Thinking Sphinx and would rather use a more up-to-date version of the former, recent releases of Thinking Sphinx do not have it included any longer.

As for AfterCommit and Riddle, while they are still included for plugin installs, they’re no longer in the Thinking Sphinx gem (since 1.3.3). Instead, they are considered dependencies, and will be installed as separate gems.

Filtering on String Attributes

While you can have string columns as attributes in Sphinx, they aren’t stored as strings. Instead, Sphinx figures out the alphabetical order, and gives each string an integer value to make them useful for sorting. However, this means it’s close to impossible to filter on these attributes.

So, to get around this, there’s two options: firstly, use integer attributes instead, if you possibly can. This works for small result sets (for example: gender). Otherwise, you might want to consider manually converting the string to a CRC integer value:

has "CRC32(category)", :as => :category, :type => :integer

This way, you can filter on it like so: 'pancakes', :with => {
  :category => 'Ruby'.to_crc32

Of course, this isn’t amazingly clean, but it will work quite well. You should also take note that CRC32 encoding can have collisions, so it’s not the perfect solution.

Models outside of app/models

If you’re using plugins or other web frameworks (Radiant, Ramaze, etc) that don’t always store their models in app/models, you can tell Thinking Sphinx to look in other locations when building the configuration file:

  model_directories << "/path/to/models/dir"

By default, Thinking Sphinx will load all models in app/models and vendor/plugins/*/app/models.

Using Thinking Sphinx with Bundler

If you’re using Thinking Sphinx with the gem manager Bundler, you will need to set the :require option to thinking_sphinx.

gem 'thinking-sphinx',
  :version => '1.3.17',
  :require => 'thinking_sphinx'

If this isn’t done, it can introduce issues with gem loading order and script/console. And don’t forget that you will still need to explicitly request the Thinking Sphinx tasks in your Rakefile:

require 'thinking_sphinx/tasks'

Mixing Ranged Filters and OR Logic

While Sphinx allows for querying with ranged filters on attributes, you can’t have multiple filters joined by OR logic – all must match.

As a way around this, you might want to construct a SQL snippet which returns specific values for each range interval, and then filter by an array of values for the intervals you want. Check out Tiago’s solution on the Google Group.

This won’t suit all situations, of course – if you don’t have specific range intervals, then you’re going to have to try something else.

Removing HTML from Excerpts

For a while, Thinking Sphinx auto-escaped excerpts. However, Sphinx itself can remove HTML entities for indexing and excerpts, which is a better way to approach this. So, you’ll want to add the following setting to your sphinx.yml file:

html_strip: true

Using other Database Adapters

If you’re using Thinking Sphinx in combination with a database adapter that isn’t quite run-of-the-mill, you may need to add a snippet of code to a Rails initialiser or equivalent (This is only available in versions 1.4.0 and 2.0.0 onwards, though).

Here’s an example that covers things for Octopus:

ThinkingSphinx.database_adapter = lambda do |model|
  case model.connection.config[:adapter]
  when 'mysql', 'mysql2'
  when 'postgresql'
    raise "You can only use Thinking Sphinx with MySQL or PostgreSQL"

Of course, ThinkingSphinx.database_adapter accepts a symbol as well, if you just want to presume that you’ll always be using either MySQL or PostgreSQL:

ThinkingSphinx.database_adapter = :postgresql

In most situations, though, you shouldn’t need to do this. Thinking Sphinx understands the standard MySQL, PostgreSQL, MySQL2, MySQL Plus and NullDB (as MySQL) adapters.

Using OR Logic with Attribute Filters

It is possible to filter on attributes using OR logic – although you need to be using Sphinx 0.9.9 or newer.

There’s two steps to it… firstly, you need to create a computed attribute while searching, using Sphinx’s select option, and then filter by that computed value. Here’s an example where we want to return all publicly visible articles, as well as articles belonging to the user with an ID of 5.

with_display = "*, IF(visible = 1 OR user_id = 5, 1, 0) AS display" 'pancakes',
  :sphinx_select => with_display,
  :with          => {'display' => 1}

It’s important to note that you’ll want to include all existing attribute values by default (that’s the * at the start of the select). It’s quite similar to standard SQL syntax.

For further reading, I recommend Sphinx’s documentation on both the select option and expression syntax.

Catching Exceptions when Searching

By default, Thinking Sphinx does not execute the search query until you examine your search results – which is usually in the view. This is so you can chain sphinx scopes without sending multiple (unnecessary) queries to Sphinx.

However, this means that exceptions will be fired from within the view – and most people put their exception handling in the controller. To force exceptions to fire when you actually define the search, all you need to do is to inform Thinking Sphinx that it should populate the results immediately: 'pancakes', :populate => true

Obviously, if you’re chaining scopes together, make sure you add this at the end with a final search call: :populate => true

Slow Requests (Especially in Development)

If you’re finding a lot of requests are quite slow (particularly in your local development environment), this could be because you have a lot of models. Thinking Sphinx loads all models to determine which ones are indexed by Sphinx (this is necessary to load search results), but you can make things much faster by setting out a list of indexed models in your config/sphinx.yml file.

Errors saying no fields are defined

If you have defined fields (using the indexes method) but you’re getting an error saying none are defined, it could be due to other gems packaging custom (and perhaps broken) versions of the BlankSlate gem. To get around this, add the proper BlankSlate gem to your Gemfile above thinking-sphinx:

gem 'blankslate', ''
# ...
gem 'thinking-sphinx', '2.0.11'