I would like to write a Python macro that upon opening my QGIS project file will reload the default style for each layer from the PostgreSQL 'layer_style' table. I have had a look at the documentation and can only work out how this is done from an SQLite .db or .qml file.
Any pointers?
Resurrecting the topic with QGIS 3.0 :). Looking at the QgsVectorLayer API documentation instead of QgsMapLayer API, you have the answer. You can use method saveStyleToDatabase
There are related recipes to manipulate styles in PostgreSQL database from QGIS Python tests including saveStyleToDatabase case at https://github.com/qgis/QGIS/blob/master/tests/src/python/test_provider_postgres.py#L1553
