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OpenERP/Odoo : Difference of read() and browse() calls!

Hello Community,

Recently there has been a discussion going on whether its good to use read() or browse() in OpenERP/Odoo.

This discussion was even launched earlier too way back in 2011, some suggestions have also float around.

The community has been active on this thread and here are the answers compiled and hence can be useful for anyone.

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Using read() is a bad practice. read() is used for web-services calls but in your own method calls you should always use browse(). Not only, it allows s a better quality of the code, but it's also better for the performance.

- read() calls name_get() for many2one fields producing extra SQL queries you probably don't need.
- browse() is optimized for prefetching and auto-load of fields.

It's true that browse() may load a few fields you do not need (not all). It prefetches stored fields, because those fields do not costs anything to load in terms of performance. It's very complex to optimize for performance with read() when the code is complex (involves loops, other method calls). Whereas, with browse(), the framework do the optimization job for you.

Usually, code implemented with read are often with complexities of O(n) or O(n²) as soon as there is loops in your methods. But codes written with browse() are automatically O(1) if browse is called at the beginning of your computations. (not inside loops)

Want a small example? Try this code on res.partner:

for company in self.browse(cr, uid, ids, context=context):
for people in company.child_ids: print company.name,
people.country_id.code

The above will do 6 SQL queries, whatever the length of ids and number of people/countries. (if IDS>200, he will split into subqueries)

The same code with read(), you will probably end up with 3*len(ids) + 3 queries.

Do This: for record in self.browse():
....
Not This:

for foo in bars:
record = self.browse()
....
--
In the first instance the SQL query for the records is done once, at the beginning, but in the second it is being called once for every iteration of the loop.

Long story short: browse() scale, read() not. (even in v7 or preceding versions) We will add more inputs once community updates it.

Thanks.