Elasticsearch коннектор#

Примечание

Ниже приведена оригинальная документация Trino. Скоро мы ее переведем на русский язык и дополним полезными примерами.

The Elasticsearch Connector allows access to Elasticsearch data from Trino. This document describes how to setup the Elasticsearch Connector to run SQL queries against Elasticsearch.

Примечание

Elasticsearch (6.6.0 or later) or OpenSearch (1.1.0 or later) is required.

Configuration#

To configure the Elasticsearch connector, create a catalog properties file etc/catalog/example.properties with the following contents, replacing the properties as appropriate for your setup:

connector.name=elasticsearch
elasticsearch.host=localhost
elasticsearch.port=9200
elasticsearch.default-schema-name=default

Configuration properties#

Elasticsearch configuration properties#

Property name

Description

Default

elasticsearch.host

The comma-separated list of host names for the Elasticsearch node to connect to. This property is required.

elasticsearch.port

Port of the Elasticsearch node to connect to.

9200

elasticsearch.default-schema-name

The schema that contains all tables defined without a qualifying schema name.

default

elasticsearch.scroll-size

Sets the maximum number of hits that can be returned with each Elasticsearch scroll request.

1000

elasticsearch.scroll-timeout

Amount of time Elasticsearch keeps the search context alive for scroll requests.

1m

elasticsearch.request-timeout

Timeout value for all Elasticsearch requests.

10s

elasticsearch.connect-timeout

Timeout value for all Elasticsearch connection attempts.

1s

elasticsearch.backoff-init-delay

The minimum duration between backpressure retry attempts for a single request to Elasticsearch. Setting it too low might overwhelm an already struggling ES cluster.

500ms

elasticsearch.backoff-max-delay

The maximum duration between backpressure retry attempts for a single request to Elasticsearch.

20s

elasticsearch.max-retry-time

The maximum duration across all retry attempts for a single request to Elasticsearch.

20s

elasticsearch.node-refresh-interval

How often the list of available Elasticsearch nodes is refreshed.

1m

elasticsearch.ignore-publish-address

Disables using the address published by Elasticsearch to connect for queries.

TLS security#

The Elasticsearch connector provides additional security options to support Elasticsearch clusters that have been configured to use TLS.

If your cluster has globally-trusted certificates, you should only need to enable TLS. If you require custom configuration for certificates, the connector supports key stores and trust stores in PEM or Java Key Store (JKS) format.

The allowed configuration values are:

TLS Security Properties#

Property name

Description

elasticsearch.tls.enabled

Enables TLS security.

elasticsearch.tls.keystore-path

The path to the PEM or JKS key store.

elasticsearch.tls.truststore-path

The path to PEM or JKS trust store.

elasticsearch.tls.keystore-password

The key password for the key store specified by elasticsearch.tls.keystore-path.

elasticsearch.tls.truststore-password

The key password for the trust store specified by elasticsearch.tls.truststore-path.

Type mapping#

Because Trino and Elasticsearch each support types that the other does not, this connector maps some types when reading data.

Elasticsearch type to Trino type mapping#

The connector maps Elasticsearch types to the corresponding Trino types according to the following table:

Elasticsearch type to Trino type mapping#

Elasticsearch type

Trino type

Notes

BOOLEAN

BOOLEAN

DOUBLE

DOUBLE

FLOAT

REAL

BYTE

TINYINT

SHORT

SMALLINT

INTEGER

INTEGER

LONG

BIGINT

KEYWORD

VARCHAR

TEXT

VARCHAR

DATE

TIMESTAMP

For more information, see Date types.

IPADDRESS

IP

No other types are supported.

Array types#

Fields in Elasticsearch can contain zero or more values , but there is no dedicated array type. To indicate a field contains an array, it can be annotated in a Trino-specific structure in the _meta section of the index mapping.

For example, you can have an Elasticsearch index that contains documents with the following structure:

{
    "array_string_field": ["trino","the","lean","machine-ohs"],
    "long_field": 314159265359,
    "id_field": "564e6982-88ee-4498-aa98-df9e3f6b6109",
    "timestamp_field": "1987-09-17T06:22:48.000Z",
    "object_field": {
        "array_int_field": [86,75,309],
        "int_field": 2
    }
}

The array fields of this structure can be defined by using the following command to add the field property definition to the _meta.trino property of the target index mapping.

curl --request PUT \
    --url localhost:9200/doc/_mapping \
    --header 'content-type: application/json' \
    --data '
{
    "_meta": {
        "trino":{
            "array_string_field":{
                "isArray":true
            },
            "object_field":{
                "array_int_field":{
                    "isArray":true
                }
            },
        }
    }
}'

Примечание

It is not allowed to use asRawJson and isArray flags simultaneously for the same column.

Date types#

Elasticsearch supports a wide array of date formats including built-in date formats and also custom date formats. The Elasticsearch connector supports only the default date type. All other date formats including built-in date formats and custom date formats are not supported. Dates with the format property are ignored.

Raw JSON transform#

There are many occurrences where documents in Elasticsearch have more complex structures that are not represented in the mapping. For example, a single keyword field can have widely different content including a single keyword value, an array, or a multidimensional keyword array with any level of nesting.

curl --request PUT \
    --url localhost:9200/doc/_mapping \
    --header 'content-type: application/json' \
    --data '
{
    "properties": {
        "array_string_field":{
            "type": "keyword"
        }
    }
}'

Notice for the array_string_field that all the following documents are legal for Elasticsearch. See the Elasticsearch array documentation for more details.

[
    {
        "array_string_field": "trino"
    },
    {
        "array_string_field": ["trino","is","the","besto"]
    },
    {
        "array_string_field": ["trino",["is","the","besto"]]
    },
    {
        "array_string_field": ["trino",["is",["the","besto"]]]
    }
]

Further, Elasticsearch supports types, such as dense_vector, that are not supported in Trino. New types are constantly emerging which can cause parsing exceptions for users that use of these types in Elasticsearch. To manage all of these scenarios, you can transform fields to raw JSON by annotating it in a Trino-specific structure in the _meta section of the index mapping. This indicates to Trino that the field, and all nested fields beneath, need to be cast to a VARCHAR field that contains the raw JSON content. These fields can be defined by using the following command to add the field property definition to the _meta.presto property of the target index mapping.

curl --request PUT \
    --url localhost:9200/doc/_mapping \
    --header 'content-type: application/json' \
    --data '
{
    "_meta": {
        "presto":{
            "array_string_field":{
                "asRawJson":true
            }
        }
    }
}'

This preceding configurations causes Trino to return the array_string_field field as a VARCHAR containing raw JSON. You can parse these fields with the built-in JSON functions.

Примечание

It is not allowed to use asRawJson and isArray flags simultaneously for the same column.

Special columns#

The following hidden columns are available:

Column

Description

_id

The Elasticsearch document ID

_score

The document score returned by the Elasticsearch query

_source

The source of the original document

Full text queries#

Trino SQL queries can be combined with Elasticsearch queries by providing the full text query as part of the table name, separated by a colon. For example:

SELECT * FROM "tweets: +trino SQL^2"

Predicate push down#

The connector supports predicate push down of below data types:

Elasticsearch

Trino

Supports

binary

VARBINARY

NO

boolean

BOOLEAN

YES

double

DOUBLE

YES

float

REAL

YES

byte

TINYINT

YES

short

SMALLINT

YES

integer

INTEGER

YES

long

BIGINT

YES

keyword

VARCHAR

YES

text

VARCHAR

NO

date

TIMESTAMP

YES

ip

IPADDRESS

NO

(all others)

(unsupported)

(unsupported)

AWS authorization#

To enable AWS authorization using IAM policies, the elasticsearch.security option needs to be set to AWS. Additionally, the following options need to be configured appropriately:

Property name

Description

elasticsearch.aws.region

AWS region or the Elasticsearch endpoint. This option is required.

elasticsearch.aws.access-key

AWS access key to use to connect to the Elasticsearch domain. If not set, the Default AWS Credentials Provider chain will be used.

elasticsearch.aws.secret-key

AWS secret key to use to connect to the Elasticsearch domain. If not set, the Default AWS Credentials Provider chain will be used.

elasticsearch.aws.iam-role

Optional ARN of an IAM Role to assume to connect to the Elasticsearch domain. Note: the configured IAM user has to be able to assume this role.

elasticsearch.aws.external-id

Optional external ID to pass while assuming an AWS IAM Role.

Password authentication#

To enable password authentication, the elasticsearch.security option needs to be set to PASSWORD. Additionally the following options need to be configured appropriately:

Property name

Description

elasticsearch.auth.user

User name to use to connect to Elasticsearch.

elasticsearch.auth.password

Password to use to connect to Elasticsearch.

SQL support#

The connector provides globally available and read operation statements to access data and metadata in the Elasticsearch catalog.

Table functions#

The connector provides specific table functions to access Elasticsearch.

raw_query(varchar) -> table#

The raw_query function allows you to query the underlying database directly. This function requires Elastic Query DSL syntax, because the full query is pushed down and processed in Elasticsearch. This can be useful for accessing native features which are not available in Trino or for improving query performance in situations where running a query natively may be faster.

Предупреждение

Нативный запрос, переданный в источник, должен возвращать набор записей (result set). CedrusData не осуществляет проверку доступа текущего пользователя к объектам источника, задействованным в нативном запросе. Используйте нативные запросы только для чтения данных.

The raw_query function requires three parameters:

  • schema: The schema in the catalog that the query is to be executed on.

  • index: The index in Elasticsearch to be searched.

  • query: The query to be executed, written in Elastic Query DSL.

Once executed, the query returns a single row containing the resulting JSON payload returned by Elasticsearch.

For example, query the example catalog and use the raw_query table function to search for documents in the orders index where the country name is ALGERIA:

SELECT
  *
FROM
  TABLE(
    example.system.raw_query(
      schema => 'sales',
      index => 'orders',
      query => '{
        "query": {
          "match": {
            "name": "ALGERIA"
          }
        }
      }'
    )
  );

Примечание

Полиморфные табличные функции не сохраняют оригинальный порядок записей в результате запроса. Есть переданный запрос содержит запрос выражение ORDER BY, функция может вернуть записи в ином порядке. Для восстановления требуемого порядка используйте ORDER BY в запросе CedrusData.