Check for missing fields

You want to find documents where a field is absent or present.

IS NULL and IS NOT NULL

-- Find users without an email
SELECT * FROM users WHERE email IS NULL

-- Find users with an email
SELECT * FROM users WHERE email IS NOT NULL

-- Combine with other filters
SELECT * FROM users WHERE category = 'eng' AND email IS NULL

IS NULL translates to ismissing(@email) and the negation to -ismissing(@email).

Requires Redis 7.4+ (RediSearch 2.10+) and the field must be declared with INDEXMISSING in the index schema. A UserWarning is emitted at translation time as a reminder.

exists() for SELECT and HAVING

exists() is a different mechanism. It runs through FT.AGGREGATE and APPLY, returning 1 or 0 per row rather than filtering them out.

-- Add a 0/1 column
SELECT name, exists(email) AS has_email FROM users

-- Filter via HAVING
SELECT name FROM users HAVING exists(email) = 1

-- Multiple checks
SELECT name, exists(email) AS has_email, exists(phone) AS has_phone FROM users

exists() does not require INDEXMISSING on the field, but it cannot be used in WHERE. Use IS NULL / IS NOT NULL to filter rows by presence.