Comment 16 for bug 2071374

Reviewed: https://review.opendev.org/c/openstack/neutron/+/923496
Committed: https://opendev.org/openstack/neutron/commit/a73ef23e3fca625b82d59c4e2aa10b8d8736d78b
Submitter: "Zuul (22348)"
Branch: stable/2023.2

commit a73ef23e3fca625b82d59c4e2aa10b8d8736d78b
Author: Roberto Bartzen Acosta <email address hidden>
Date: Thu Jun 27 18:29:37 2024 +0000

    Change to use selectin for RBACs in SubnetPool DB load strategy

    To solve a performance issue when using network rbacs with thousands
    of entries in the subnets, networks, and networks rbacs tables, it's
    necessary to change the eager loader strategy to not create and process
    a "cartesian" product of thousands of unnecessary combinatios for the
    purpose of the relationship included between rbac rules and subnetpool
    database model.

    We don't need a many-to-many relationship here. So, we can use the
    selectin eager loading to make this relationship one-to-many and create
    the model with only the necessary steps, without exploding into a
    thousands of rows caused by the "left outer join" cascade.

    The "total" queries from this process would be divided into a series of
    smaller queries with much better performance, and the resulting huge
    select query will be resolved much faster without joined cascade,
    representing significant performance gains.

    Closes-bug: #2071374
    Change-Id: I2e4fa0ffd2ad091ab6928bdf0d440b082c37def2
    (cherry picked from commit 46edf255bde0603fe88b2dd9f4e482590e384382)