Sequel::CountComparisons

This gem adds three methods to Sequel::Dataset:

• #count_equals?
• #count_less_than?
• #count_greater_than?

These methods allow you to efficiently compare a dataset's row count to a given number.

Why use this gem?

• It generates efficient SQL queries to minimize database overhead, using LIMIT and OFFSET clauses to count only the rows needed. This is especially useful for large datasets.
• It provides a readable API for expressing dataset count comparisons, which makes code easier to understand and less error-prone.

Install the gem and add to the application's Gemfile by executing:

$ bundle add sequel_count_comparisons

If Bundler is not being used to manage dependencies, install the gem by executing:

$ gem install sequel_count_comparisons

You can load this extension into specific datasets:

ds = DB[:table].extension(:count_comparisons)

Or you can load it into all of a database’s datasets:

DB.extension(:count_comparisons)

DB[:table].count_equals?(1)
# SELECT EXISTS (SELECT 1 FROM table OFFSET 0) AND NOT EXISTS (SELECT 1 FROM table OFFSET 1)

DB[:table].count_equals?(0)
# SELECT 1 FROM table LIMIT 1

DB[:table].count_greater_than?(0)
# SELECT 1 FROM table LIMIT 1

DB[:table].count_greater_than?(1)
# SELECT 1 FROM table LIMIT 1 OFFSET 1

DB[:table].count_less_than?(1)
# SELECT 1 FROM table LIMIT 1

DB[:table].count_less_than?(5)
# SELECT 1 FROM table LIMIT 1 OFFSET 4

The gem is tested on PostgreSQL. It may or may not work for other databases.

This library is released under the MIT License.

Bug reports and pull requests are welcome on GitHub at https://github.com/eriklovmo/sequel_count_comparisons.