delete all vs destroy all

Question

I am looking for the best approach to delete records from a table  For instance  I have a user whose user ID is across many tables  I want to delete this user and every record that has his ID in all tables   u   User find by name  JohnBoy   u usage indexes destroy all u sources destroy all u user stats destroy all u delete   This works and removes all references of the user from all tables  but I heard that destroy all was very process heavy  so I tried delete all  It only removes the user from his own user table and the id from all the other tables are made null  but leaves the records intact in them  Can someone share what the correct process is for performing a task like this    I see that destroy all calls the destroy function on all associated objects but I just want to confirm the correct approach

User · Answer

delete all is a single SQL DELETE statement and nothing more  destroy all calls destroy   on all matching results of  conditions  if you have one  which could be at least NUM OF RESULTS SQL statements     If you have to do something drastic such as destroy all   on large dataset  I would probably not do it from the app and handle it manually with care   If the dataset is small enough  you wouldn t hurt as much

User · Answer

I   ve made a small gem that can alleviate the need to manually delete associated records in some circumstances   This gem adds a new option for ActiveRecord associations  dependent   delete recursively When you destroy a record  all records that are associated using this option will be deleted recursively  i e  across models   without instantiating any of them  Note that  just like dependent   delete or dependent   delete all  this new option does not trigger the around before after destroy callbacks of the dependent records  However  it is possible to have dependent   destroy associations anywhere within a chain of models that are otherwise associated with dependent   delete recursively  The  destroy option will work normally anywhere up or down the line  instantiating and destroying all relevant records and thus also triggering their callbacks

User · Answer

To avoid the fact that destroy all instantiates all the records and destroys them one at a time  you can use it directly from the model class   So instead of    u   User find by name  JohnBoy   u usage indexes destroy all   You can do    u   User find by name  JohnBoy   UsageIndex destroy all  user id     u id     The result is one query to destroy all the associated records

User · Answer

You are right  If you want to delete the User and all associated objects -  destroy all However  if you just want to delete the User without suppressing all associated objects -  delete all  According to this post   Rails  dependent   gt   destroy VS  dependent   gt   delete all   destroy   destroy all  The associated objects are destroyed alongside this object by calling their destroy method delete   delete all  All associated objects are destroyed immediately without calling their  destroy method

[ruby-on-rails] delete_all vs destroy_all?

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