Unique token filter

Unique token filter

Removes duplicate tokens from a stream. For example, you can use the unique filter to change the lazy lazy dog to the lazy dog.

If the only_on_same_position parameter is set to true, the unique filter removes only duplicate tokens in the same position.

When only_on_same_position is true, the unique filter works the same as remove_duplicates filter.

Example

The following analyze API request uses the unique filter to remove duplicate tokens from the quick fox jumps the lazy fox:

  1. GET _analyze
  2. {
  3.   "tokenizer" : "whitespace",
  4.   "filter" : ["unique"],
  5.   "text" : "the quick fox jumps the lazy fox"
  6. }

The filter removes duplicated tokens for the and fox, producing the following output:

  1. [ the, quick, fox, jumps, lazy ]

Add to an analyzer

The following create index API request uses the unique filter to configure a new custom analyzer.

  1. PUT custom_unique_example
  2. {
  3.   "settings" : {
  4.     "analysis" : {
  5.       "analyzer" : {
  6.         "standard_truncate" : {
  7.         "tokenizer" : "standard",
  8.         "filter" : ["unique"]
  9.         }
  10.       }
  11.     }
  12.   }
  13. }

Configurable parameters

only_on_same_position

(Optional, Boolean) If true, only remove duplicate tokens in the same position. Defaults to false.

Customize

To customize the unique filter, duplicate it to create the basis for a new custom token filter. You can modify the filter using its configurable parameters.

For example, the following request creates a custom unique filter with only_on_same_position set to true.

  1. PUT letter_unique_pos_example
  2. {
  3.   "settings": {
  4.     "analysis": {
  5.       "analyzer": {
  6.         "letter_unique_pos": {
  7.           "tokenizer": "letter",
  8.           "filter": [ "unique_pos" ]
  9.         }
  10.       },
  11.       "filter": {
  12.         "unique_pos": {
  13.           "type": "unique",
  14.           "only_on_same_position": true
  15.         }
  16.       }
  17.     }
  18.   }
  19. }