can you perhaps place a "pdb.set_trace()" inside of session._flush()?
using the debugger you can see the source of every flush() call.
Generally, it occurs each time a query is about to emit SQL.
On Mon, May 7, 2018 at 9:37 PM, Colton Allen <cmanalle...@gmail.com> wrote:
> What exactly causes the session to flush? I'm trying to track down a nasty
> bug in my versioning system.
>
> Sorry for the long code dump. I retooled
> examples/versioned_history/history_meta.py so it should look familiar. The
> function that's breaking is "column_has_changed". I've added some logs as
> well.
>
> # WHEN IT WORKS!
>
> CRITICAL:root:BEFORE MAPPING NEW VALUES
> CRITICAL:root:BEFORE SAVE
> CRITICAL:root:BEFORE REVISE
> CRITICAL:root:CHECK COLUMN CHANGES
> CRITICAL:root:AFTER REVISE
> CRITICAL:root:flush!
> CRITICAL:root:AFTER SAVE
> CRITICAL:root:flush!
>
> # WHEN IT DOESN'T WORK!
>
> CRITICAL:root:BEFORE MAPPING NEW VALUES
> CRITICAL:root:BEFORE SAVE
> CRITICAL:root:BEFORE REVISE
> CRITICAL:root:flush!
> CRITICAL:root:CHECK COLUMN CHANGES
> CRITICAL:root:AFTER REVISE
> CRITICAL:root:AFTER SAVE
> CRITICAL:root:flush!
>
> controller.py
>
> for k, v in dict.items():
> setattr(model, k, v)
> model.revise()
> db.session.add(model)
> db.session.commit()
>
> model.py
>
> class RevisionMixin:
> """Version control manager."""
>
> def revise(self):
> db.session.add(self)
> write_revision(self)
>
> version.py
>
> def write_revision(target):
> target_mapper = orm.object_mapper(target)
> revision_class = target.__versioned__['model']
> revision_mapper = revision_class.__mapper__
>
> object_changed = False
> state = {}
>
> for column in iter_mapper_columns(target_mapper, revision_mapper):
> state[column.key] = getattr(target, column.key)
> column_changed = column_has_changed(target, column.key)
> object_changed = object_changed or column_changed
>
> for relationship, changed in iter_relationships(target, target_mapper):
> if hasattr(revision_class, relationship.key):
> state[relationship.key] = getattr(target, relationship.key)
> object_changed = object_changed or changed
>
> if not isinstance(target.id, str) or object_changed:
> _write_revision(target, state)
>
>
> def _write_revision(target, state):
> version = target.version or 0
> version = version + 1
> state['version'] = version
> state['updated_at'] = db.now()
> state['primary'] = target
>
> revision = target.__versioned__['model'](**state)
> db.session.add(revision)
>
> target.version = version
> target.updated_at = state['updated_at']
>
>
> def iter_mapper_columns(primary, revision):
> mappers = zip(primary.iterate_to_root(), revision.iterate_to_root())
> for om, hm in mappers:
> if hm.single:
> continue
> for column in iter_shared_columns(om, hm):
> yield column
>
>
> def iter_shared_columns(mapper, comparison_mapper):
> for comparison_mapper_column in comparison_mapper.local_table.c:
> if 'version_meta' in comparison_mapper_column.info:
> continue
>
> try:
> mapper_column =
> mapper.local_table.c[comparison_mapper_column.key]
> yield mapper.get_property_by_column(mapper_column)
> except UnmappedColumnError:
> continue
>
>
> def iter_relationships(target, mapper):
> for prop in mapper.iterate_properties:
> if isinstance(prop, RelationshipProperty):
> passive = attributes.PASSIVE_NO_INITIALIZE
> changed = attributes.get_history(
> target, prop.key, passive=passive).has_changes()
> yield prop, changed
>
>
> def column_has_changed(target, column_name):
> # Sometimes the instance state history can't be properly
> # calculated? No flushing during versioning. Unsure why its not
> # working.
> added, _, deleted = attributes.get_history(target, column_name)
> return bool(added or deleted)
>
>
> def relationship_has_changed(prop):
> for p in prop.local_columns:
> if p.foreign_keys:
> return True
> return False
>
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
> To post example code, please provide an MCVE: Minimal, Complete, and
> Verifiable Example. See http://stackoverflow.com/help/mcve for a full
> description.
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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