"description": "a string, representing a relation ID"
}, {
"arg": "aggregate",
"description": "a string corresponding to the aggregate to calculate. Valid options are:<br /><ul><li>count</li><li>count_distinct</li><li>count_missing</li><li>min</li><li>max</li><li>sum</li><li>mean</li><li>median</li><li>stdev</li><li>stdevsample</li><li>range</li><li>minority</li><li>majority</li><li>q1: first quartile</li><li>q3: third quartile</li><li>iqr: inter quartile range</li><li>min_length: minimum string length</li><li>max_length: maximum string length</li><li>concatenate: join strings with a concatenator</li><li>concatenate_unique: join unique strings with a concatenator</li><li>collect: create an aggregated multipart geometry</li><li>array_agg: create an array of aggregated values</li></ul>"
}, {
"arg": "expression",
"description": "sub expression or field name to aggregate"
}, {
"arg": "concatenator",
"optional": true,
"default": "''",
"description": "optional string to use to join values for 'concatenate' aggregate"
}, {
"arg": "order_by",
"optional": true,
"description": "optional expression to order the features used for calculating the aggregate. Fields and geometry are from the features on the joined layer. By default, the features will be returned in an unspecified order."
