AI Functions

AI Functions are built-in functions in ClickHouse that you can use to call AI or generate embeddings to work with your data, extract information, classify data, etc...

Note

AI functions can return unpredictable outputs. The result will highly depend on the quality of the prompt and the model used.

All functions are sharing a common infrastructure that provides:

Quota enforcement: Per-query limits on tokens (ai_function_max_input_tokens_per_query, ai_function_max_output_tokens_per_query) and API calls (ai_function_max_api_calls_per_query).
Retry with backoff: Transient failures are retried (ai_function_max_retries) with exponential backoff (ai_function_retry_initial_delay_ms).

Configuration

AI functions reference a named collection that stores provider credentials and configuration. The first argument to each function is the name of this collection.

Example statement to create a named collection with provider credentials:

CREATE NAMED COLLECTION ai_credentials AS
    provider = 'openai',
    endpoint = 'https://api.openai.com/v1/chat/completions',
    model = 'gpt-4o-mini',
    api_key = 'sk-...';

Named collection parameters

Parameter	Type	Default	Description
`provider`	String	—	Model provider. Supported: `'openai'`, `'anthropic'`. See note below.
`endpoint`	String	—	API endpoint URL.
`model`	String	—	Model name (e.g. `'gpt-4o-mini'`, `'text-embedding-3-small'`).
`api_key`	String	—	Authentication key for the provider.
`max_tokens`	UInt64	`1024`	Maximum number of output tokens per API call.
`api_version`	String	—	API version string. Used by Anthropic (`'2023-06-01'`).

Note

Any OpenAI-compatible API (e.g. vLLM, Ollama, LiteLLM) can be used by setting provider = 'openai' and pointing the endpoint to your service.

Query-level settings

All AI-related settings are listed in Settings under the ai_function_ prefix.

Restricting endpoint hosts

The endpoint URL in an AI named collection is an outbound destination the server connects to under its own identity, carrying the named collection's api_key in the request headers. By default, ClickHouse permits any host. To restrict functions to a specific set of providers, configure remote_url_allow_hosts in the server config, e.g.:

<remote_url_allow_hosts>
    <host>api.openai.com</host>
    <host>api.anthropic.com</host>
</remote_url_allow_hosts>

Note that this setting is server-wide and applies to all HTTP-using features.

Supported providers

Provider	`provider` value	Chat functions	Notes
OpenAI	`'openai'`	Yes	Default provider.
Anthropic	`'anthropic'`	Yes	Uses `/v1/messages` endpoint.

Observability

AI function activity is tracked through ClickHouse ProfileEvents:

ProfileEvent	Description
`AIAPICalls`	Number of HTTP requests made to the AI provider.
`AIInputTokens`	Total input tokens consumed.
`AIOutputTokens`	Total output tokens consumed.
`AIRowsProcessed`	Number of rows that received a result.
`AIRowsSkipped`	Number of rows skipped (quota exceeded, or error with `ai_function_throw_on_error = 0`).

Query these events:

SELECT
    ProfileEvents['AIAPICalls'] AS api_calls,
    ProfileEvents['AIInputTokens'] AS input_tokens,
    ProfileEvents['AIOutputTokens'] AS output_tokens
FROM system.query_log
WHERE query_id = 'query_id'
AND type = 'QueryFinish'
ORDER BY event_time DESC;

aiClassify

Introduced in: v26.4.0

Classifies the given text into one of the provided categories using an LLM provider.

The function sends the text together with a fixed classification prompt and a JSON-schema response format constraining the model to return exactly one of the supplied labels. When the response is returned as a JSON object of the form {"category": "..."}, the label is unwrapped and the label string is returned.

The first argument is a named collection that specifies the provider, model, endpoint, and API key.

Syntax

aiClassify(collection, text, categories[, temperature])

Aliases: AIClassify

Arguments

collection — Name of a named collection containing provider credentials and configuration. String
text — Text to classify. String
categories — Constant list of candidate category labels. Array(String)
temperature — Sampling temperature controlling randomness. Default: 0.0. Float64

Returned value

One of the provided category labels, or the default value for the column type (empty string) if the request failed and ai_function_throw_on_error is disabled. String

Examples

Classify sentiment

SELECT aiClassify('ai_credentials', 'I love this product!', ['positive', 'negative', 'neutral'])

positive

Classify a column

SELECT body, aiClassify('ai_credentials', body, ['bug', 'question', 'feature']) AS kind FROM issues LIMIT 5

aiEmbed

Introduced in: v26.6.0

Generates an embedding vector for the given text using the configured AI provider.

The function sends the text to the configured embedding endpoint and returns the resulting vector as Array(Float32). Within a single block of rows, inputs are grouped into batches of up to ai_function_embedding_max_batch_size entries per HTTP request to reduce per-call overhead.

The first argument is a named collection that specifies the provider, model, endpoint, and API key. The optional dimensions argument, when supported by the model (e.g. OpenAI's text-embedding-3-*), requests a vector of the given size; otherwise the model's native size is returned.

Syntax

aiEmbed(collection, text[, dimensions])

Arguments

collection — Name of a named collection containing provider credentials and configuration. String
text — Text to embed. String
dimensions — Optional target dimensionality for the output vector. 0 or omitted means the model's native size. UInt64

Returned value

The embedding vector, or an empty array if the input is NULL or empty, the request failed and ai_function_throw_on_error is disabled, or a quota was exceeded with ai_function_throw_on_quota_exceeded disabled. Array(Float32)

Examples

Embed a single string

SELECT aiEmbed('ai_credentials', 'Hello world')

With explicit dimensions

SELECT aiEmbed('ai_credentials', 'Hello world', 256)

Embed a column of texts

SELECT aiEmbed('ai_credentials', title, 256) FROM articles LIMIT 10

aiExtract

Introduced in: v26.4.0

Extracts structured information from unstructured text using an LLM provider.

The third argument may be either a free-form natural-language instruction (e.g. 'the main complaint') or a JSON-encoded schema of the form '{"field_a": "description of field a", "field_b": "description of field b"}'.

In instruction mode, the function returns the extracted value as a plain string, or an empty string if nothing was found. In schema mode, the function returns a JSON object string whose keys match the requested schema; missing fields are null.

The first argument is a named collection that specifies the provider, model, endpoint, and API key.

Syntax

aiExtract(collection, text, instruction_or_schema[, temperature])

Aliases: AIExtract

Arguments

collection — Name of a named collection containing provider credentials and configuration. String
text — Text to extract information from. String
instruction_or_schema — Free-form extraction instruction, or a constant JSON object describing the fields to extract. const String
temperature — Sampling temperature controlling randomness. Default: 0.0. const Float64

Returned value

A single extracted value (instruction mode) or a JSON object string (schema mode). Returns the default value for the column type (empty string) if the request failed and ai_function_throw_on_error is disabled. String

Examples

Free-form instruction

SELECT aiExtract('ai_credentials', 'The package arrived late and was damaged.', 'the main complaint')

late and damaged package

Schema extraction

SELECT aiExtract('ai_credentials', review, '{"sentiment": "positive, negative or neutral", "topic": "main topic of the review"}') FROM reviews LIMIT 5

aiGenerate

Introduced in: v26.4.0

Generates free-form text content from a prompt using an LLM provider.

The function sends the prompt to the configured AI provider and returns the generated text. An optional system prompt can be provided to guide the model's behavior (e.g. tone, format, role). If no system prompt is given, the default system prompt is: You are a helpful assistant. Provide a clear and concise response.

The first argument is a named collection that specifies the provider, model, endpoint, and API key.

Syntax

aiGenerate(collection, prompt[, system_prompt[, temperature]])

Aliases: AIGenerate

Arguments

collection — Name of a named collection containing provider credentials and configuration. String
prompt — The user prompt or question to send to the model. String
system_prompt — Optional constant system-level instruction that guides the model's behavior (e.g. persona, output format), sent along with each prompt. String
temperature — Sampling temperature controlling randomness. Default: 0.7. Float64

Returned value

The generated text response, or the default value for the column type (empty string) if the request failed and ai_function_throw_on_error is disabled. String

Examples

Simple question

SELECT aiGenerate('ai_credentials', 'What is 2 + 2? Reply with just the number.')

With system prompt

SELECT aiGenerate('ai_credentials', 'Explain ClickHouse', 'You are a database expert. Be concise.')

Summarize column values

SELECT article_title, aiGenerate('ai_credentials', concat('Summarize in one sentence: ', article_body)) AS summary FROM articles LIMIT 5

aiTranslate

Introduced in: v26.4.0

Translates the given text into the specified target language using an LLM provider.

Additional style or dialect instructions may be passed as a fourth argument (e.g. 'keep technical terms untranslated').

The first argument is a named collection that specifies the provider, model, endpoint, and API key.

Syntax

aiTranslate(collection, text, target_language[, instructions[, temperature]])

Aliases: AITranslate

Arguments

collection — Name of a named collection containing provider credentials and configuration. String
text — Text to translate. String
target_language — Target language name or BCP-47 code (e.g. 'French', 'es-MX'). String
instructions — Optional constant additional instructions for the translator. String
temperature — Sampling temperature controlling randomness. Default: 0.3. Float64

Returned value

The translated text, or the default value for the column type (empty string) if the request failed and ai_function_throw_on_error is disabled. String

Examples

Translate to French

SELECT aiTranslate('ai_credentials', 'Hello, world!', 'French')

Bonjour le monde!

Translate to Japanese with style instructions

SELECT aiTranslate('ai_credentials', body, 'Japanese', 'Use polite form (desu/masu)') FROM articles LIMIT 5

Configuration​

Named collection parameters​

Query-level settings​

Restricting endpoint hosts​

Supported providers​

Observability​

aiClassify​

aiEmbed​

aiExtract​

aiGenerate​

aiTranslate​

Configuration

Named collection parameters

Query-level settings

Restricting endpoint hosts

Supported providers

Observability

aiClassify

aiEmbed

aiExtract

aiGenerate

aiTranslate