arangodb/Documentation/DocuBlocks/ensureHashIndex.md

@brief ensures that a non-unique hash index exists collection.ensureIndex({ type: "hash", fields: [ "field1", ..., "fieldn" ] })

Creates a non-unique hash index on all documents using field1, ... fieldn as attribute paths. At least one attribute path has to be given. The index will be non-sparse by default.

To create a sparse unique index, set the sparse attribute to true:

collection.ensureIndex({ type: "hash", fields: [ "field1", ..., "fieldn" ], sparse: true })

In case that the index was successfully created, an object with the index details, including the index-identifier, is returned.

@EXAMPLE_ARANGOSH_OUTPUT{ensureHashIndex} ~db._create("test"); db.test.ensureIndex({ type: "hash", fields: [ "a" ] }); db.test.save({ a : 1 }); db.test.save({ a : 1 }); db.test.save({ a : null }); ~db._drop("test"); @END_EXAMPLE_ARANGOSH_OUTPUT