{
  "name": "overlay_equals",
  "type": "function",
  "groups": ["GeometryGroup"],
  "description": "Returns whether the current feature spatially equals to at least one feature from a target layer, or an array of expression-based results for the features in the target layer that are spatially equal to the current feature.<br><br>Read more on the underlying GEOS \"Equals\" predicate, as described in PostGIS <a href='https://postgis.net/docs/ST_Equals.html'>ST_Equals</a> function.",
  "arguments": [{
    "arg": "layer",
    "description": "the layer whose overlay is checked"
  }, {
    "arg": "expression",
    "description": "an optional expression to evaluate on the features from the target 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 target features to check. If not set, all the features will be checked.",
    "optional": true
  }, {
    "arg": "limit",
    "description": "an optional integer to limit the number of matching features. If not set, all the matching 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": "overlay_equals('regions')",
    "returns": "TRUE if the current feature is spatially equal to a region"
  }, {
    "expression": "overlay_equals('regions', filter:= population > 10000)",
    "returns": "TRUE if the current feature is spatially equal to a region with a population greater than 10000"
  }, {
    "expression": "overlay_equals('regions', name)",
    "returns": "an array of names, for the regions spatially equal to the current feature"
  }, {
    "expression": "array_to_string(overlay_equals('regions', name))",
    "returns": "a string as a comma separated list of names, for the regions spatially equal to the current feature"
  }, {
    "expression": "array_sort(overlay_equals(layer:='regions', expression:=\"name\", filter:= population > 10000))",
    "returns": "an ordered array of names, for the regions spatially equal to the current feature and with a population greater than 10000"
  }, {
    "expression": "overlay_equals(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2)",
    "returns": "an array of geometries (in WKT), for up to two regions spatially equal to the current feature"
  }],
  "tags": ["predicate", "current", "equals", "equal", "target", "array", "geos", "st_equals", "described", "underlying", "features"]
}