arangodb/Documentation/DocuBlocks/collectionEnsureGeoConstraint.md

@brief ensures that a geo index exists collection.ensureIndex({ type: "geo", fields: [ "location" ] })

Since ArangoDB 2.5, this method is an alias for ensureGeoIndex since geo indexes are always sparse, meaning that documents that do not contain the index attributes or have non-numeric values in the index attributes will not be indexed.