Commit 0c7e2833 authored by Markus Holtermann's avatar Markus Holtermann
Browse files

[1.8.x] Fixed #24554 -- Sped up migrations by rendering initial apps when they are first needed 

Calling Migration.mutate_state() now also allows to do in_place
mutations in case an intermediate state is thrown away later.

Thanks Anssi Kääriäinen for the idea, Ryan Hall for parts of the patch,
and Claude Paroz and Tim Graham for the review

Backport of 57dc8dd3 from master
parent 9e991470

django/db/migrations/executor.py

+14 −7
Original line number Diff line number Diff line
@@ -74,20 +74,27 @@ class MigrationExecutor(object): 
        migrations_to_run = {m[0] for m in plan}

        # Create the forwards plan Django would follow on an empty database

        full_plan = self.migration_plan(self.loader.graph.leaf_nodes(), clean_start=True)

        # Holds all states right before and right after a migration is applied

        # Holds all states right before a migration is applied

        # if the migration is being run.

        states = {}

        state = ProjectState(real_apps=list(self.loader.unmigrated_apps))

        if self.progress_callback:

            self.progress_callback("render_start")

        # Phase 1 -- Store all project states of migrations right before they

        # are applied. The first migration that will be applied in phase 2 will

        # trigger the rendering of the initial project state. From this time on

        # models will be recursively reloaded as explained in

        # `django.db.migrations.state.get_related_models_recursive()`.

        for migration, _ in full_plan:

            do_run = migration in migrations_to_run

            if do_run:

                if 'apps' not in state.__dict__:

                    state.apps  # Render all real_apps -- performance critical

                states[migration] = state.clone()

            # Only preserve the state if the migration is being run later

            state = migration.mutate_state(state, preserve=do_run)

        if self.progress_callback:

            self.progress_callback("render_success")

        # Phase 1 -- Store all required states

        for migration, _ in full_plan:

            if migration in migrations_to_run:

                states[migration] = state.clone()

            state = migration.mutate_state(state)  # state is cloned inside

        # Phase 2 -- Run the migrations

        for migration, backwards in plan:

            if not backwards:

django/db/migrations/graph.py

+1 −1
Original line number Diff line number Diff line
@@ -228,7 +228,7 @@ class MigrationGraph(object): 
                    plan.append(migration)

        project_state = ProjectState(real_apps=real_apps)

        for node in plan:

            project_state = self.nodes[node].mutate_state(project_state)

            project_state = self.nodes[node].mutate_state(project_state, preserve=False)

        return project_state



    def __contains__(self, node):

django/db/migrations/migration.py

+7 −3
Original line number Diff line number Diff line
@@ -69,12 +69,16 @@ class Migration(object): 
    def __hash__(self):

        return hash("%s.%s" % (self.app_label, self.name))



    def mutate_state(self, project_state):

    def mutate_state(self, project_state, preserve=True):

        """

        Takes a ProjectState and returns a new one with the migration's

        operations applied to it.

        operations applied to it. Preserves the original object state by

        default and will return a mutated state from a copy.

        """

        new_state = project_state

        if preserve:

            new_state = project_state.clone()



        for operation in self.operations:

            operation.state_forwards(self.app_label, new_state)

        return new_state

django/db/migrations/state.py

+6 −0
Original line number Diff line number Diff line
@@ -35,6 +35,12 @@ def get_related_models_recursive(model): 
    """

    Returns all models that have a direct or indirect relationship

    to the given model.



    Relationships are either defined by explicit relational fields, like

    ForeignKey, ManyToManyField or OneToOneField, or by inheriting from another

    model (a superclass is related to its subclasses, but not vice versa). Note,

    however, that a model inheriting from a concrete model is also related to

    its superclass through the implicit *_ptr OneToOneField on the subclass.

    """

    def _related_models(m):

        return [