change_table with Bulk Option Combines Multiple alter-table Statements

Today I learned that when doing database-migration on Rails, change_table :#{table_name}, bulk: true let us combine multiple alter-table statements and it could reduce the cost of the whole alteration. That is, instead of executing multiple alter-table separately, def change add_column :users, :first_name, :string, null: false add_column :users, :last_name, :string, null: false end we can run a single alter-table statement by change_table like as follows. def change change_table :users, bulk: true do |t| t.

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RSpec's #to Method Takes the 2nd Argument As Its failing-message

Today I learned that RSpec's #to method takes the 2nd argument as its custom failing-message. expect(actual_value).to eq(expected_value), message Let's say we are going to test a JSON object. The following example expects a part of the JSON object response_json['eye_colour'] to be "blue". require 'net/https' require 'uri' require 'json' RSpec.describe do example do response = Net::HTTP.get_response(URI('')) response_json = JSON.parse(response.body) expect(response_json['eye_colour']).to eq('blue') end end Unfortunately, this test fails and displays messages like this:

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How to Fix PostgreSQL Error: canceling statement due to conflict with recovery

Today I learned how to fix a PostgreSQL error like this: ERROR: canceling statement due to conflict with recovery DETAIL: User query might have needed to see row versions that must be removed. It's about database replication. I have been getting that on read-only database which uses PostgreSQL Hot Standby. This error didn't happen always but happened occasionally. I fixed that by setting both max_standby_archive_delay and max_standby_streaming_delay to a longer time (300s) on the standby servers.

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`sole` Method Is Going to Be Introduced into ActiveRecord and Enumerable

Today I learned that Rails 6.1.3 does not have methods that raise exceptions when more than one record was found. However, in future versions, we could use ActiveRecord::FinderMethods#sole for that purpose. It seems Enumerable#sole is also going to be introduced. Sometimes I need to make sure there is one and only one record that matches a condition without using a unique-index, for example, when I cannot add that constraint to the database.

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Format with to_s Methods ActiveSupport Provides

Today I learned/remembered that to format a number with a delimiter, we can use ActiveSupport::NumericWithFormat#to_s(:delimited). require 'active_support' require 'active_support/core_ext' 123456789.to_s(:delimited) # => "123,456,789" Not only that, but this method also provides other formats and takes options to tweak its behavior. 123456789.to_s(:delimited, delimiter: '-') # => "123-456-789" 123456789.to_s(:currency, precision: 3) # => "$123,456,789.000" 123456789.to_s(:human_size) # => "118 MB" 123456789.to_s(:human) # => "123 Million" Originally, when I need to format a number to a delimited number, I would try to use number_to_delimited provided by ActiveSupport::NumberHelper.

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Gentaro "hibariya" Terada

Otaka-no-mori, Chiba, Japan
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Loves Ruby, Internet, and Programming.