QGIS/resources/function_help/json/geometry_overlay_within

{
  "name": "geometry_overlay_within",
  "type": "function",
    "description": "Performs a spatial join of type WITHIN. This returns an array of results of an expression evaluated on features from a different layer that are WITHIN the current feature, or, if no expression if provided, simply returns whether at least one feature from the other layer is WITHIN the current feature.",
    "arguments": [
    {
      "arg": "layer",
      "description": "the other layer"
    },
    {
      "arg": "expression",
      "description": "an optional expression to evaluate on the features from the other layer (if not set, the function will just return a boolean indicating whether there is at least one match)",
      "optional": true
    },
    {
      "arg": "filter",
      "description": "an optional expression to filter the matching features (if not set, all features will be returned)",
      "optional": true
    },
    {
      "arg": "limit",
      "description": "an optional integer to limit the number of matching features (if not set, all features will be returned)",
      "optional": true
    },
    {
      "arg": "cache",
      "description": "set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)",
      "optional": true,
      "default": false
    }
  ],
  "examples": [
    {
      "expression": "geometry_overlay_within('regions')",
      "returns": "True"
    },
    {
      "expression": "geometry_overlay_within('regions', name)",
      "returns": "['South Africa', 'Africa', 'World']"
    },
    {
      "expression": "geometry_overlay_within('regions', name, name != 'World')",
      "returns": "['South Africa', 'Africa']"
    },
    {
      "expression": "geometry_overlay_within('regions', name, limit:=1)",
      "returns": "['South Africa']"
    }
  ]
}