Created
March 6, 2012 10:21
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How to make an activerecord model use a tempory table or view dynamically per query
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# Creating view or temp table | |
ActiveRecord::Base.connection.execute("CREATE TEMPORARY TABLE users#{args.offset} SELECT * FROM users LIMIT #{limit} OFFSET #{(args.offset - 1) * limit}") | |
# or | |
ActiveRecord::Base.connection.execute("CREATE VIEW users#{args.offset} AS SELECT * FROM users LIMIT #{limit} OFFSET #{(args.offset - 1) * limit}") | |
### Giving relation back, suitable for find_in_batches | |
#User.arel_table.name ='users2' | |
# This changes table name in FROM part of the query | |
# User.scoped.find_in_batches | |
# ActiveRecord::StatementInvalid: Mysql2::Error: Unknown table 'users': SELECT `users`.* FROM `users2` WHERE (`users2`.`id` >= 0) ORDER BY users.id ASC LIMIT 1000 | |
#User.table_name = 'users2' | |
# This changes the SELECT part | |
# 1.9.2p290 :022 > User.all.count | |
# ActiveRecord::StatementInvalid: Mysql2::Error: Unknown table 'users2': SELECT `users2`.* FROM `users` | |
# So both needed, this way queries will use temp table or view. | |
User.arel_table.name ='users2' | |
User.table_name = 'users2' | |
User.all | |
# Joins may behave strangely afterwards | |
### | |
### Not giving relation back ### | |
User.find_by_sql('SELECT * FROM USERS') |
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