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feat: only offline the subset that matches all layer's filters #138

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suricactus merged 1 commit into from
Mar 3, 2026
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feat: only offline the subset that matches all layer's filters #138

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26 changes: 25 additions & 1 deletion libqfieldsync/offliners.py
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Original file line number Diff line number Diff line change
Expand Up @@ -403,12 +403,13 @@ def _convert_to_offline_project(
driver = ogr.GetDriverByName("GPKG")
data_source = driver.CreateDataSource(offline_gpkg_path)
datasource_mapping = self._get_datasource_mapping(project, offline_layers)
filters_mapping = self._get_filters_mapping(datasource_mapping)

for layer_infos in datasource_mapping.values():
layer_to_offline = layer_infos[0].layer
self.create_layer(layer_to_offline, data_source, offline_gpkg_path)

for layer_infos in datasource_mapping.values():
for datasource_hash, layer_infos in datasource_mapping.items():
request = QgsFeatureRequest()
# All layers for given `datasource_hash` are pointing to the very same file/datasource.
# Here we get the first layer for convenience, but it doesn't really matter.
Expand Down Expand Up @@ -439,6 +440,9 @@ def _convert_to_offline_project(
layer_bbox = tr.transform(bbox)
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@nirvn nirvn Feb 27, 2026

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Not related to the change in this PR, but since I see it now and it's an important one, I shall speak ;)

You should wrap this transform around a try / except. If the transform fails, QGIS throws a QgsCsException. Without catching that, I suspect here what will happen is that we'll either silently fail or the whole offline will fail due to a parent try / except.

If we catch it here, it'll allow us to decide whether we want to a/ stop the export and provide clear guidance on how to resolve failure (i.e., fix your extent), b/ offline the whole layer without being filtered by a bounding box, or c/ offline the layer with zero feature in it.

I'm leaning towards option b or c, and I can think of multiple reasons why either are good 😆

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@suricactus suricactus Mar 3, 2026 •
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see #139

request.setFilterRect(layer_bbox)

if filters_mapping[datasource_hash]:
request.setFilterExpression(filters_mapping[datasource_hash])

source = self.convert_to_offline_layer(
layer_to_offline, data_source, offline_gpkg_path, request
)
Expand All @@ -465,6 +469,26 @@ def _convert_to_offline_project(
project.writePath(offline_gpkg_path),
)

def _get_filters_mapping(
self, datasource_mapping: Dict[str, List[LayerInfo]]
) -> Dict[str, str]:
"""Get mapping of filter strings to be applied for each datasource. If no filters to be applied, the value will be an empty string."""
filters_by_datasource = {}

for datasource_hash, layer_infos in datasource_mapping.items():
filters = []
for layer_info in layer_infos:
if layer_info.subset_string.strip():
filters.append(f"({layer_info.subset_string})")
else:
# if there is no subset string, we don't need to apply any filter, as it means "all features"
filters = []
break

filters_by_datasource[datasource_hash] = " OR ".join(filters)

return filters_by_datasource

def _get_datasource_mapping(
self,
project: QgsProject,
Expand Down
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