Fetch all table name and row count for specific table with Rails? - mysql

Question

How can i fetch all the table name and row count for the specific table from the specific database ?
Result
Table Name , Row Count , Table Size(MB)
---------------------------------------
table_1 , 10 , 2.45
table_2 , 20 , 4.00

Answer 1

ActiveRecord::Base.connection.tables.each do |table|
h = ActiveRecord::Base.connection.execute("SHOW TABLE STATUS LIKE '#{table}'").fetch_hash
puts "#{h['Name']} has #{h['Rows']} rows with size: #{h['Data_length']}"
end

Answer 2

The question is tagged mysql but you can do it in a DB-agnostic manner via ORM.
class DatabaseReport
def entry_counts
table_model_names.map do |model_name|
entity = model_name.constantize rescue nil
next if entity.nil?
{ entity.to_s => entity.count }
end.compact
end
private
def table_model_names
ActiveRecord::Base.connection.tables.map(&:singularize).map(&:camelize)
end
end
Note that this will skip tables for which you don't have an object mapping such as meta tables like ar_internal_metadata or schema_migrations. It also cannot infer scoped models (but could be extended to do so). E.g. with Delayed::Job I do this:
def table_model_names
ActiveRecord::Base.connection.tables.map(&:singularize).map(&:camelize) + ["Delayed::Job"]
end

Answer 3

I came up with my own version which is also db agnostic.
As it uses the descendants directly it also handles any tables where the table_name is different to the model name.
The rescue nil exists for cases when you have the class that inherits from ActiveRecord but for some reason don't have a table associated with it. It does give data for STI classes and the parent class.
my_models = ActiveRecord::Base.descendants
results = my_models.inject({}) do |result, model|
result[model.name] = model.count rescue nil
result
end

Answer 4

#temp_table = []
ActiveRecord::Base.connection.tables.each do |table|
count = ActiveRecord::Base.connection.execute("SELECT COUNT(*) as count FROM #{table}").fetch_hash['count']
size = ActiveRecord::Base.connection.execute("SHOW TABLE STATUS LIKE '#{table}'").fetch_hash
#temp_table << {:table_name => table,
:records => count.to_i,
:size_of_table => ((BigDecimal(size['Data_length']) + BigDecimal(size['Index_length']))/1024/1024).round(2)
}
end
end