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Faster SELECTs when using Sequel with pg
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sequel_pg overwrites the inner loop of the Sequel postgres adapter row fetching code with a C version. The C version is significantly faster (2-6x) than the pure ruby version that Sequel uses by default.

Real world difference

The speed up that sequel_pg gives you depends on what you are selecting, but it should be noticable whenever many rows are selected. Here's an example that shows the difference it makes on a couple of models:

$ irb -r model -r benchmark 
irb(main):001:0> Track.count
=> 140854
irb(main):002:0> Album.count
=> 5579
irb(main):003:0> puts Benchmark.measure{Track.each{}}
 10.740000   0.190000  10.930000 ( 11.875343)
=> nil
irb(main):004:0> puts Benchmark.measure{10.times{Album.each{}}}
  7.920000   0.070000   7.990000 (  8.482130)
=> nil
irb(main):005:0> require '/data/code/sequel_pg/ext/sequel_pg/sequel_pg'
=> true
irb(main):006:0> puts Benchmark.measure{Track.each{}}
  2.360000   0.400000   2.760000 (  3.723098)
=> nil
irb(main):007:0> puts Benchmark.measure{10.times{Album.each{}}}
  1.300000   0.190000   1.490000 (  2.001393)
=> nil

Here's an example that uses a modified version of swift's benchmarks (

benchmark         sys       user      total     real     rss
sequel #select    0.090000  2.020000  2.110000  2.246688 46.54m
sequel_pg #select 0.000000  0.250000  0.250000  0.361999  7.33m

Installing the gem

gem install sequel_pg

The standard gem requires compiling from source, so you need a working compiler toolchain. Since few Windows users have a working compiler toolchain, a windows binary gem is available that works on both 1.8 and 1.9.

Running the specs

sequel_pg doesn't ship with it's own specs. It's designed to replace a part of Sequel, so it just uses Sequel's specs. Specifically, the spec_postgres spec from Sequel.

Reporting issues/bugs

sequel_pg uses GitHub Issues for tracking issues/bugs:


The source code is on GitHub:

To get a copy:

git clone git://

There are only a few requirements, which you should probably have before considering use of the library:

  • Rake

  • Sequel

  • pg

  • libpq headers and library


To build the library from a git checkout, after installing the requirements:

rake build

Platforms Supported

sequel_pg has been tested on the following:

Operating Systems/Platforms

  • Linux (i386)

  • OpenBSD (amd64, i386)

  • Windows XP (i386)

Compiler Versions

  • gcc (3.3.5, 4.2.1, 4.4.3)

Ruby Versions

  • jruby cext branch (compiles but untested and unusable, as pg itself doesn't compile yet)

  • rbx head

  • ruby 1.8.6

  • ruby 1.8.7

  • ruby 1.9.1

  • ruby 1.9.2

  • ruby head

If your platform, compiler version, or ruby version is not listed above, please test and send me a report including:

* Your operating system and platform (e.g. i386, x86_64/amd64)
* Your compiler
* Your ruby version

Known Issues

  • You must be using the ISO PostgreSQL date format (which is the default). Using the SQL, POSTGRESQL, or GERMAN date formats will result in incorrect date/timestamp handling. In addition to PostgreSQL defaulting to ISO, Sequel also manually sets the date format to ISO by default, so unless you are overriding that setting (via Sequel::Postgres.use_iso_date_format = false), you should be OK.

  • Adding your own type conversion procs to Sequel::Postgres::PG_TYPES only has an effect if those types are not handled by default.

  • The named_timezones plugin does not integrate with sequel_pg, since sequel_pg does it's own timestamp conversions. The :local and :utc settings for database_timestamp and application_timestamp do work, as does setting the datetime_class to DateTime.


Jeremy Evans <>

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