Explore, filter and export without writing SQL

1How FilterMate works

FilterMate applies a subset filter to your vector layers. Nothing is deleted or copied: the filtered layer simply shows only the features that match, exactly as if you had typed a provider filter in the layer properties. FilterMate builds that filter for you, in the native language of the data source (PostGIS SQL, SpatiaLite SQL or a QGIS expression for files).

Every spatial filter follows the same three-part pattern:

Attribute-only filters also work: with no target layers and no predicate, FilterMate filters the source layer itself on the features you selected in the Exploring zone. Filters can be chained with AND, OR and AND NOT, undone, redone, saved as favorites, and exported to a new file or GeoPackage project.

2Installation

From the QGIS plugin repository (recommended)

1. In QGIS, open Plugins → Manage and Install Plugins…
2. Search for FilterMate in the All tab and click Install Plugin.
3. A FilterMate button appears in the plugin toolbar. Click it to open the panel.

Manual installation

Download the ZIP from GitHub Releases, then either use Install from ZIP in the plugin manager or unzip it into your profile's plugin folder:

Optional: PostgreSQL / PostGIS

FilterMate filters PostGIS layers server-side. This needs the psycopg2 Python package inside the QGIS Python environment:

pip install psycopg2-binary

On Windows, run it from the OSGeo4W Shell that ships with QGIS. Without it, PostgreSQL layers still work through the generic OGR backend, only slower.

3The panel at a glance

FilterMate is a dock panel. By default it opens on the right side of the QGIS window and can be moved, floated or resized like any other QGIS panel.

The panel is made of four areas, from top to bottom:

4Exploring a layer

The Exploring zone works on the current layer, shown in the first row of the Filtering tab. By default it follows the layer selected in the QGIS Layers panel (the auto current layer button, first in the Filtering rail). Turn that button off to pick the layer manually from the drop-down.

Three selection modes are available. Ticking one un-ticks the others, and the header of each box expands or collapses it.

Single selection

Pick one feature from a searchable drop-down. The second row is the display expression: FilterMate detects a sensible name field automatically (name, label, id…) but you can type any QGIS expression, for instance "code" || ' - ' || "name". The blue arrows step to the previous or next feature.

Multiple selection

Tick as many features as you need. The list loads at most 1000 rows (configurable) so that huge layers never freeze QGIS. When the list is truncated, typing in the filter box searches the whole layer, and Select All in the right-click menu loads everything.

Custom selection (expression)

Write a QGIS expression; every feature it matches becomes part of the reference geometry. This is the mode to use for "all features": an always-true expression such as 1 or TRUE takes the whole source layer.

The exploring rail

The vertical buttons to the left of the selection boxes, from top to bottom:

Each layer remembers its own exploring settings in the project, so switching layers and coming back restores your selection.

5The Filtering tab

Each row of the Filtering tab is switched on and off by the button in the rail on its left. A row that is switched off is ignored when you press Filter, which lets you keep a buffer or a predicate configured without using it.

Row by row

The eight predicates

Buffers

• Positive buffer, e.g. 50 m: "everything within 50 m of the selected road". Use Intersect as the predicate.
• Negative buffer, e.g. -20 m on a polygon: keeps only the features well inside it, away from the edges.
• Expression buffer: the distance is evaluated per source feature, so a regulatory distance can come from an attribute.
• Distances are always in metres. Layers in a geographic CRS (degrees) are reprojected on the fly.

Centroids

The two centroid checkboxes replace polygons by a representative point (a point guaranteed to be on the surface) during the test. With very detailed polygons this can make a cascade several times faster, at the cost of exactness on the borders. FilterMate keeps the spatial index usable in both cases.

6Tutorial: your first spatial filter

Goal: show only the buildings and hedges within 50 m of one road. The screenshots use a small BD TOPO extract (one commune, 373 buildings, 130 road sections) stored in a GeoPackage, but any project with a line layer and a polygon layer will do.

Each step below shows the whole QGIS window, so you can check the map canvas and the panel against your own screen. The map extent is the same from step 2 to step 6.

1. Choose the source layer. Load your layers and open FilterMate. In the Layers panel, click the road layer: it becomes the source layer (the auto current layer button is on by default) and the Exploring zone switches to it.

   

2. Pick the reference road. In the Exploring zone, tick Single selection and choose a road in the drop-down. The canvas selects it (yellow). If the drop-down shows identifiers rather than names, change the display field in the row below.

   

3. Choose the target layers. Open the Filtering tab. Switch on Layers to filter (second rail button) and tick batiment and haie in the list.

   

4. Choose the predicate. Switch on Geometric predicates and make sure Intersect is ticked.

   

5. Add a buffer. Switch on Buffer value and type 50. The buffer type row (Round, 5 segments) can stay as it is.

   

6. Run the filter. Press the Filter button (first button of the action bar). The map canvas is frozen for the duration of the task and redrawn once at the end.

   

What FilterMate generated for the GeoPackage buildings layer, as you can read it in Layer Properties → Source → Provider Feature Filter:

ROWID IN (SELECT id FROM "rtree_batiment_geom"
          WHERE minx <= 598540.4 AND maxx >= 598349.4
            AND miny <= 6265342.3 AND maxy >= 6265157.7)
AND ST_Intersects("geom",
      ST_Buffer(ST_MakeValid(ST_GeomFromText('LineString (…)', 2154)), 50.0))

The first clause queries the GeoPackage R-tree so that SQLite only evaluates the expensive predicate on candidate rows. That is what turns a 6-minute cascade on a 37-layer project into a 3-second one.

7Action bar, undo and history

Buttons are greyed out when they cannot apply: Undo before any filter, Redo when nothing was undone, Export while the Exporting tab is not configured.

8Favorites

A favorite stores a complete filter: source layer, selection, predicates, buffer and target layers. Re-applying it takes one click, which makes favorites the natural way to keep regulatory or recurring queries.

The favorites menu

• Add filter saves the filter currently applied. It is disabled when no filter is active.
• Saved favorites are listed in the Quick filtering section at the top: one click applies them.
• Manage favorites… opens the manager described below.
• Export… / Import… exchange favorites as JSON files between projects or colleagues.
• Global favorites lists the favorites shared across all your projects.
• Maintenance holds database statistics and cleanup tools.

The favorites manager

• General: rename the favorite, add a description and tags, see its source layer, provider and usage count. Visibility switches between This project and All projects (global).
• Expression: the exact filter expression, editable for advanced users.
• Remote: publishing to a shared git repository. FilterMate uses the QGIS authentication manager for credentials, so a team can maintain a common library of filters. This requires the optional QGIS Resource Sharing plugin.

Apply runs the favorite on the current project, Save Changes stores your edits, Delete removes it. Favorites are stored in FilterMate's own SQLite database in your QGIS profile and, for project-scoped ones, in the project file too.

9Exporting

The Exporting tab writes the currently visible features of the chosen layers to disk, filters included. As in the Filtering tab, each row is enabled by its rail button.

GeoPackage projects

When the output format is GeoPackage and several layers are exported together, FilterMate embeds a QGIS project in the file with the layer group hierarchy, styles and CRS preserved. Before writing, a recap dialog lists what will be exported and lets you keep or flatten the group structure. Opening the resulting .gpkg in QGIS restores the whole map.

10Configuration

The Configuration tab exposes FilterMate's settings as a tree. Double-click a value to edit it; drop-down values offer their allowed choices. Most changes apply live, a few (dock position, UI profile) need the panel to be closed and reopened.

The tree also holds performance thresholds (when to switch optimisations on), the expression cache size, export defaults and the Extensions section (favorites sharing, QFieldCloud). The complete file lives at config/config.json in the plugin folder; config/config.default.json next to it documents every key and can be copied back to reset everything.

11Backends and performance

FilterMate picks a backend per layer, based on its data provider, and shows it in the header badge. The backend decides where the spatial test runs: in the database whenever possible, in QGIS otherwise.

Measured on real projects with version 4.8.9 (timings from filtermate.log):

• The map canvas is frozen during a filter task and redrawn once, so the interface stays responsive.
• Click the backend badge to see the backends available for the current layer and force one when the automatic choice is not what you want.
• Every step above a few milliseconds is logged with a ⏱ prefix; compare two runs by grepping the log.

12Processing Toolbox

FilterMate registers a Processing provider. Its first algorithm, filtermate:batch_filter, applies one filter expression to several vector layers in a single run. Because it is a regular Processing algorithm it can be used in the graphical modeler, in batch mode, or from Python:

import processing
processing.run("filtermate:batch_filter", {
    "INPUT_LAYERS": ["batiment", "haie"],
    "EXPRESSION": "\"etat_de_l_objet\" = 'En service'",
})

13Troubleshooting

Where to look first

• QGIS Log Messages panel, FilterMate tab: warnings and errors of the current session.
• logs/filtermate.log in the plugin folder: the full log, including ⏱ timing lines. Set the environment variable FILTERMATE_LOG_LEVEL=DEBUG before starting QGIS for a verbose log.
• Switch FEEDBACK_LEVEL to verbose in the Configuration tab to see every message in the message bar.

Common questions

Getting help

• Report bugs with the log excerpt on GitHub Issues.
• Ask questions on the Discord server.
• Watch the video tutorials.