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Expression function "feature_id()" #51116

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andreasneumann opened this issue Dec 5, 2022 · 0 comments · Fixed by #51441
Closed

Expression function "feature_id()" #51116

andreasneumann opened this issue Dec 5, 2022 · 0 comments · Fixed by #51441
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Expressions Related to the QGIS expression engine or specific expression functions Feature Request

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@andreasneumann
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Feature description

A new expression function feature_id() would be useful in order to get the internal id of a certain feature in another (related) layer.

As parameters, there could be different variations, e.g.:

feature_id(layer,pkey_value)

assuming that the other layer knows which column contains the pkey.

or

feature_id(layer,pkey_column,pkey_value)

if the layer doesn't know the pkey column name.

or

feature_id(feature)

not sure if it is possible? A feature might not be unique, even if it contains a geometry?

Additional context

This is useful when working on expressions with multiple related layers. There are some expressions that require the "internal feature id" as an input parameter.
@andreasneumann andreasneumann added Feature Request Expressions Related to the QGIS expression engine or specific expression functions labels Dec 5, 2022
nyalldawson added a commit to nyalldawson/QGIS that referenced this issue Jan 11, 2023
@nyalldawson
[feature][expressions] Add feature_id(some feature) function
9f3da8a 
Allows for retrieving the feature ID of a feature object. Accepts
one argument which must be a feature object. Accordingly this
function can be used with the results of any other function
which returns feature objects, such as "get_feature", "overlay_*",
etc.

Fixes qgis#51116
@nyalldawson nyalldawson mentioned this issue Jan 11, 2023
Merged
nyalldawson added a commit that referenced this issue Jan 13, 2023
@nyalldawson
[feature][expressions] Add feature_id(some feature) function
390cb76 
Allows for retrieving the feature ID of a feature object. Accepts
one argument which must be a feature object. Accordingly this
function can be used with the results of any other function
which returns feature objects, such as "get_feature", "overlay_*",
etc.

Fixes #51116
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Add feature_id(some feature) function nyalldawson/QGIS
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@andreasneumann