The shape of a dataset is not preserved when a run is exported to another database

[simonzihlmann]

As the title says, the shape of a dataset is not preserved when it is exported from one database to another one. See below for more details.

Steps to reproduce

1. generate a dummy dataset

initialise_or_create_database_at("./source.db")
# Setting up a doNd measurement
sweep_1 = LinSweep(dac.ch1, -1, 1, 20, 0.01)
sweep_2 = LinSweep(dac.ch2, -1, 1, 20, 0.01)
dond(
    sweep_1,                          # 1st independent parameter
    sweep_2,                          # 2nd independent parameter
    dmm.v1,                           # 1st dependent parameter
    dmm.v2,                           # 2nd dependent parameter
    measurement_name="dond_example",  # Set the measurement name
    exp=tutorial_exp,                 # Set the experiment to save data to.
    show_progress=True                # Optional progress bar
)
ds_source = load_by_run_spec(experiment_name='tutorial_exp', captured_run_id=1)
ds_source.get_parameter_data('dmm_v1')['dmm_v1']['dmm_v1'].shape

2. Extract it to another database

from qcodes.dataset.sqlite.database import connect
source_path = os.path.join(os.getcwd(), './source.db')
target_path = os.path.join(os.getcwd(), './target.db')
source_conn = connect(source_path)
target_conn = connect(target_path)
extract_runs_into_db(source_path, target_path, 1)

3. load it from the new database

initialise_or_create_database_at("./target.db")
ds_target = load_by_run_spec(experiment_name='tutorial_exp', captured_run_id=1)
ds_target.get_parameter_data('dmm_v1')['dmm_v1']['dmm_v1'].shape

Expected behaviour

ds_source.get_parameter_data('dmm_v1')['dmm_v1']['dmm_v1'].shape and ds_target.get_parameter_data('dmm_v1')['dmm_v1']['dmm_v1'].shape should return in both cases (20, 20)

Actual behaviour

ds_source.get_parameter_data('dmm_v1')['dmm_v1']['dmm_v1'].shape returns (20, 20)
ds_target.get_parameter_data('dmm_v1')['dmm_v1']['dmm_v1'].shape returns (400,)

It would be nice if the shape would be preserved as it facilitates further data processing.

System

operating system
Win10

If you are using a released version of qcodes (recommended):
0.32.0

[simonzihlmann]

@jenshnielsen thanks for this rapid fix.