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Support default expression and expression indexes for MySQL #34307
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MySQL 8.0.13 and higher supports functional key parts that index expression values rather than column or column prefix values. https://dev.mysql.com/doc/refman/8.0/en/create-index.html
MySQL 8.0.13 and higher supports default value to be a function or expression. https://dev.mysql.com/doc/refman/8.0/en/create-table.html
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lengths = options.delete(:lengths) | ||
|
||
columns = index[-2].map { |name| | ||
[ name.to_sym, expressions[name] || +quote_column_name(name) ] |
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Why would we want to dup quote_column_name(name)
here?
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This is because the quoted columns would be mutated by add_index_length
and add_index_sort_order
:
rails/activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb
Lines 109 to 112 in a3dcba4
def add_index_length(quoted_columns, **options) | |
lengths = options_for_index_columns(options[:length]) | |
quoted_columns.each do |name, column| | |
column << "(#{lengths[name]})" if lengths[name].present? |
rails/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
Lines 1195 to 1198 in a3dcba4
def add_index_sort_order(quoted_columns, **options) | |
orders = options_for_index_columns(options[:order]) | |
quoted_columns.each do |name, column| | |
column << " #{orders[name].upcase}" if orders[name].present? |
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Ah I see, I thought quote_column_name
would return something that was already duped somehow... because it is the case of
rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb
Lines 67 to 69 in 6149080
def quote_column_name(column_name) | |
column_name.to_s | |
end |
... but I didn't realise the method may always return the same object like ...
def quote_column_name(name) | |
@quoted_column_names[name] ||= "`#{super.gsub('`', '``')}`" | |
end |
... got it :)
I'm just realising that there's no way (AFAIK) to know whether a method returns an object that is referenced elsewhere or not, which is kind of sad, because we may be duplicating strings for no reason (if a method returns a new object or an existing object), maybe we should do something about that one day.
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Nevermind, I misread this whole thing 👍
Support default expression and expression indexes for MySQL rails/rails#34307
MySQL 8.0.13 is released a few days ago.
https://mysqlserverteam.com/the-mysql-8-0-13-maintenance-release-is-generally-available/
Now we can supports default expression and expression indexes for mysql2 adapter.