mask

mask replaces entity characters with a masking character. Use it for partial redaction when you need to hide selected characters while preserving useful structure such as length, separators, or visible prefixes.

Parameters

Parameter	Type	Default	Description
`masking_char`	STRING (1 char)	`"*"`	Character used for masking.
`chars_to_mask`	INT	`null`	How many characters to mask. `null` (omitted) = mask all; `0` = mask none; positive N = mask N characters.
`from_end`	BOOLEAN	`true`	When `chars_to_mask` is set, count from the end of the value. Set `false` to count from the start.
`mask_all_chars`	BOOLEAN	`false`	When `false`, only alphanumeric characters are masked (separators like `-` and spaces are preserved). When `true`, every character position is masked, including separators.

Example — full mask

SELECT app_public.mask(
  'SSN: 078-05-1120, Card: 4532-7891-2345-6672',
  OBJECT_CONSTRUCT(
    'entity_config', OBJECT_CONSTRUCT(
      'US_SSN', OBJECT_CONSTRUCT('operator', 'mask'),
      'CREDIT_CARD', OBJECT_CONSTRUCT(
        'operator', 'mask',
        'operator_params', OBJECT_CONSTRUCT('masking_char', 'X')
      )
    )
  )
);
-- SSN: ***-**-****, Card: XXXX-XXXX-XXXX-XXXX

Example — mask last 4 digits only

Use this when a workflow needs to hide the trailing digits while leaving the rest of the value visible:

SELECT app_public.mask(
  'Phone: 415-555-0100',
  OBJECT_CONSTRUCT(
    'entity_config', OBJECT_CONSTRUCT(
      'PHONE_NUMBER', OBJECT_CONSTRUCT(
        'operator', 'mask',
        'operator_params', OBJECT_CONSTRUCT(
          'masking_char', 'X',
          'chars_to_mask', 4,
          'from_end', TRUE
        )
      )
    )
  )
);
-- Phone: 415-555-XXXX

Example — mask_all_chars for uniform output

Mask every position, including separators. This hides punctuation and spacing, but the output still preserves entity length:

SELECT app_public.mask(
  'SSN: 078-05-1120',
  OBJECT_CONSTRUCT(
    'entity_config', OBJECT_CONSTRUCT(
      'US_SSN', OBJECT_CONSTRUCT(
        'operator', 'mask',
        'operator_params', OBJECT_CONSTRUCT('mask_all_chars', TRUE)
      )
    )
  )
);
-- SSN: ***********

When to use

Workflows that require masking specific portions of credit card numbers, phone numbers, or other structured identifiers.
Partial redaction where reviewers need to see length or format while selected characters are hidden.
When downstream workflows do not need stable replacement values for joins or grouping.

Notes

masking_char must be exactly 1 character.
When chars_to_mask > len(entity), the entire entity is masked.
Masked output preserves original length — ***-**-**** is the same length as 078-05-1120.
Partial masking can leave unmasked characters, length, and format visible. Use a stricter operator, such as constant or hash, when that remaining structure should not be exposed.