How to get all attributes from a non geometry PostGIS layer with Python in QGIS?

Question

I want to extract all attributes from a non geomety layer in QGIS with Python, but there is only the function

uniqueValues(fieldIndex)

More specific: I have a postgresql table which is loaded into QGIS with "Add PostGIS layers". Then I need all attributes from two columns in a dictionary (key: column1, value: column2). Here is my code so far:

dictAttr = {}
feature = QgsFeature()
layer.dataProvider().select(layer.dataProvider().attributeIndexes())
while layer.dataProvider().nextFeature(feature):
  attributes = feature.attributeMap()
  dictAttr[attributes[FIELD_INDEX1].toString()] = attributes[FIELD_INDEX2].toString()
return dictAttr

Problem: layer is not a geometry table, so it has no features and the while loop is never entered. And I can't use uniqueValues() because I need every attribute. Do you know any way to solve this? This can't be so hard...

Answer 1

Call select passing False as third argument (i.e. fetchGeometry):

layer.dataProvider().select(layer.dataProvider().attributeIndexes(), QgsRectangle(), False)