Saving styles for all layers using PyQGIS - SLD, QML, databases

Question

I wrote a script (for QGIS 3) that saves styles for all visible vector layers in QML and SLD files:

import processing
self=qgis.utils
layers = self.iface.mapCanvas().layers()

for layer in layers:
    layerType = layer.type()
    if layerType == QgsMapLayer.VectorLayer:
        name = layer.name()
        pathqml = 'C:/Style/QML/'+str(name)+'.qml'  
        pathsld = 'C:/Style/SLD/'+str(name)+'.sld'  
        layer.saveNamedStyle(pathqml)
        layer.saveSldStyle(pathsld)

How can I do this for the layers from SQLite, PostgreSQL/PostGIS ?

Answer 1

To save the style into a database use:

layer.saveStyleToDatabase("NameOfStyle","Description",True,"uiFileContent")

Answer 2

This is what i do to write all styles to the Postgresql database, after setting up a project:

Writing all styles to the database

mapGeometryType = {
    0: "Point",
    1: "Line",
    2: "Polygon",
    3: "UnknownGeometry",
    4: "NullGeometry",
}

layers = QgsProject.instance().mapLayers()

for layer in layers.values():
    if layer.type() == QgsMapLayer.VectorLayer:
        if mapGeometryType[layer.geometryType()] != "NullGeometry":
            layer.saveStyleToDatabase(name=layer.name(),description="Default style for {}".format(layer.name()), useAsDefault=True, uiFileContent="")

The code has an additional condition based on layer.geometryType() to avoid writing styles for non geographic data (from tables used just for joins or relations).

Styles are written on public.layer_styles table on the database where the layer comes from.