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You're viewing version 2.17 of the OpenSearch documentation. This version is no longer maintained. For the latest version, see the current documentation. For information about OpenSearch version maintenance, see Release Schedule and Maintenance Policy.

Identifiers

An identifier is an ID to name your database objects, such as index names, field names, aliases, and so on. OpenSearch supports two types of identifiers: regular identifiers and delimited identifiers.

Regular identifiers

A regular identifier is a string of characters that starts with an ASCII letter (lower or upper case). The next character can either be a letter, digit, or underscore (_). It can’t be a reserved keyword. White space and other special characters are also not allowed.

OpenSearch supports the following regular identifiers:

  1. Identifiers prefixed by a dot . sign. Use to hide an index. For example .opensearch-dashboards.
  2. Identifiers prefixed by an @ sign. Use for meta fields generated by Logstash ingestion.
  3. Identifiers with hyphen - in the middle. Use for index names with date information.
  4. Identifiers with star * present. Use for wildcard match of index patterns.

For regular identifiers, you can use the name without any back tick or escape characters. In this example, source, fields, account_number, firstname, and lastname are all identifiers. Out of these, the source field is a reserved identifier.

SELECT account_number, firstname, lastname FROM accounts;
account_number firstname lastname
1 Amber Duke
6 Hattie Bond
13 Nanette Bates
18 Dale Adams

Delimited identifiers

A delimited identifier can contain special characters not allowed by a regular identifier. You must enclose delimited identifiers with back ticks (``). Back ticks differentiate the identifier from special characters.

If the index name includes a dot (.), for example, log-2021.01.11, use delimited identifiers with back ticks to escape it `log-2021.01.11`.

Typical examples of using delimited identifiers:

  1. Identifiers with reserved keywords.
  2. Identifiers with a . present. Similarly, - to include date information.
  3. Identifiers with other special characters. For example, Unicode characters.

To quote an index name with back ticks:

source=`accounts` | fields `account_number`;
account_number
1
6
13
18

Case sensitivity

Identifiers are case sensitive. They must be exactly the same as what’s stored in OpenSearch.

For example, if you run source=Accounts, you’ll get an index not found exception because the actual index name is in lower case.

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