duplicate_columns_handler.rb

Path: lib/sequel/extensions/duplicate_columns_handler.rb
Last Update: Sun Oct 02 21:06:53 +0000 2016

frozen-string-literal: true

The duplicate_columns_handler extension allows you to customize handling of duplicate column names in your queries on a per-database or per-dataset level.

For example, you may want to raise an exception if you join 2 tables together which contains a column that will override another columns.

To use the extension, you need to load the extension into the database:

  DB.extension :duplicate_columns_handler

A database option is introduced: :on_duplicate_columns. It accepts a Symbol or any object that responds to :call.

  :on_duplicate_columns => :raise
  :on_duplicate_columns => :warn
  :on_duplicate_columns => :ignore
  :on_duplicate_columns => proc { |columns| arbitrary_condition? ? :raise : :warn }

You may also configure duplicate columns handling for a specific dataset:

  ds.on_duplicate_columns(:warn)
  ds.on_duplicate_columns(:raise)
  ds.on_duplicate_columns(:ignore)
  ds.on_duplicate_columns { |columns| arbitrary_condition? ? :raise : :warn }
  ds.on_duplicate_columns(proc { |columns| arbitrary_condition? ? :raise : :warn })

If :raise is specified, a Sequel::DuplicateColumnError is raised. If :warn is specified, you will receive a warning via `warn`. If a callable is specified, it will be called. If no on_duplicate_columns is specified, the default is :warn.

Related module: Sequel::DuplicateColumnsHandler

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