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Empty fields?

The topic of empty-ish fields comes up often because:

• input fields weren't required and were skipped (e.g. optional input fields in signup forms)
• because of human error (e.g. data entry "interns" forgot to fill out a form field)
• and last but not least, because of purposefully set empty-ish values (null, [], {}, "")

Disambiguation

Existent Fields

In Elasticsearch, these values would indicate that a given field does exist:

• Empty strings, such as "" or "-"
• Arrays containing **null and another value**, such as [null, "foo"]
• A custom [null-value](<https://www.elastic.co/guide/en/elasticsearch/reference/current/null-value.html>), defined in field mapping (discussed later on)

Non-Existent Fields

When a doc is inserted into ES, its fields are usually indexed. The indexed value of one of those fields may not exist due to a variety of reasons:

• The field is simply not present in the source JSON
• The field in the source JSON is null — null or [] or [null, null, ...?] or {}
• The field has ["index" : false](<https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-index.html>) set in the mapping
• The field value was malformed and the [ignore_malformed](<https://www.elastic.co/guide/en/elasticsearch/reference/current/ignore-malformed.html>) parameter was defined in the index mapping