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 are experimental. Set allow_experimental_ai_functions to enable them.

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. Different named collections can be created and used for different functions or functions calls. For example you may want to define a different named collection to use with the text functions (aiGenerate, aiClassify, aiExtract, aiTranslate) vs the aiEmbed function, which require different endpoints and usually use different models.

Example statement to create a named collection with provider credentials, one with a chat endpoint and another with an embedding endpoint:

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

CREATE NAMED COLLECTION ai_embedding_credentials AS
    provider = 'openai',
    endpoint = 'https://api.openai.com/v1/embeddings',
    model = 'text-embedding-3-small',
    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. Optional: when omitted, the auth header is not sent, which allows targeting OpenAI-compatible servers that do not require authentication.
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.

Selecting credentials

A function resolves the named collection to use from, in order:

1. the credentials key of its parameter map, when present;
2. otherwise the applicable default-credentials setting:
   • ai_function_text_default_credentials for the text functions (aiGenerate, aiClassify, aiExtract, aiTranslate);
   • ai_function_embedding_default_credentials for aiEmbed.

If neither is set, the call fails. The text and embedding functions use separate default settings because a chat-completions endpoint and model differ from an embeddings one.

SET ai_function_text_default_credentials = 'ai_text_credentials';

-- Uses ai_text_credentials from the setting:
SELECT aiGenerate('What is 2 + 2? Reply with just the number.');

-- Overrides the default for this call:
SELECT aiGenerate('Bonjour', map('credentials', 'other_credentials'));

Parameter map

Each function accepts an optional trailing Map(String, String) of parameters. All values are strings (quote numbers, e.g. '0.2'). Unknown keys are rejected. A key that is present overrides the corresponding named-collection value; a key that is absent falls back to the named collection (for model/max_tokens) or the built-in default.

The following parameters are common to all the AI functions:

Key	Description
credentials	Named collection to use (see above).
model	Overrides the collection's model.

Individual functions accept additional, function-specific parameters (such as max_tokens, temperature, system_prompt, instructions, and dimensions). See each function's reference below for the parameters it accepts and their defaults.

SELECT aiGenerate(body, map('temperature', '0.2', 'system_prompt', 'You are terse.')) FROM articles;

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, potentially carrying (if specified) 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.

Transport security (HTTP vs HTTPS)

The transport is determined solely by the scheme of the endpoint URL. There is no application-level encryption of the request payload; the protection of data in transit depends entirely on the scheme:

• https:// — the connection uses TLS. The request body (input text, prompts) and the api_key in the request headers are encrypted in transit, and the provider's certificate is validated. Use this for any remote provider.
• http:// — the connection is not encrypted. The request body and the api_key are sent in cleartext. Only use this for a trusted provider on a private network (e.g. a local vLLM or Ollama instance).

AI functions do not force HTTPS: an http:// endpoint is accepted and sends data unencrypted. There is currently no server-side setting that rejects cleartext AI endpoints — remote_url_allow_hosts restricts the destination host only and does not inspect the URL scheme, so an http:// endpoint to an allowed host still passes. To ensure encrypted transport, configure named collections with https:// endpoints.

Note that in either case the provider receives the input data in cleartext after TLS termination; TLS protects the data only on the network path between the server and the provider.

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.

Credentials (a named collection specifying the provider, model, endpoint, and optionally an API key) are taken from the credentials key of the optional parameter map, or from the ai_function_text_default_credentials setting when the map omits it.

Syntax

aiClassify(text, categories[, params])

Aliases: AIClassify

Arguments

• text — Text to classify. String
• categories — Constant list of candidate category labels. Array(String)
• params — Optional constant Map(String, String) of parameters. Function-specific keys: temperature (sampling temperature controlling randomness; default 0.0), max_tokens (maximum output tokens per call; default 1024). The common parameters credentials and model also apply (see AI Functions). Map(String, String)

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

positive

Classify a column with explicit credentials

SELECT body, aiClassify(body, ['bug', 'question', 'feature'], map('credentials', 'ai_text_credentials')) 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.

Credentials (a named collection specifying the provider, model, endpoint, and optionally an API key) are taken from the credentials key of the optional parameter map, or from the ai_function_embedding_default_credentials setting when the map omits it. Note that aiEmbed uses a separate default-credentials setting from the text functions, since an embeddings endpoint and model differ from a chat one.

The optional dimensions parameter, 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(text[, params])

Arguments

• text — Text to embed. String
• params — Optional constant Map(String, String) of parameters. Function-specific keys: dimensions (target dimensionality of the output vector; 0 or omitted means the model's native size). The common parameters credentials and model also apply (see AI Functions). Map(String, String)

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 (map parameter can be omitted if the ai_function_embedding_default_credentials setting is set)

SELECT aiEmbed('Hello world', map('credentials', 'ai_embedding_credentials'))

With explicit dimensions

SELECT aiEmbed('Hello world', map('credentials', 'ai_embedding_credentials', 'dimensions', '256'))

Embed a column of texts

SELECT aiEmbed(title, map('credentials', 'ai_embedding_credentials', 'dimensions', '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.

Credentials (a named collection specifying the provider, model, endpoint, and optionally an API key) are taken from the credentials key of the optional parameter map, or from the ai_function_text_default_credentials setting when the map omits it.

Syntax

aiExtract(text, instruction_or_schema[, params])

Aliases: AIExtract

Arguments

• 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
• params — Optional constant Map(String, String) of parameters. Function-specific keys: temperature (sampling temperature controlling randomness; default 0.0), max_tokens (maximum output tokens per call; default 1024). The common parameters credentials and model also apply (see AI Functions). Map(String, String)

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

late and damaged package

Schema extraction

SELECT aiExtract(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.

Credentials (a named collection specifying the provider, model, endpoint, and optionally an API key) are taken from the credentials key of the optional parameter map, or from the ai_function_text_default_credentials setting when the map omits it.

The optional parameter map may also set system_prompt (an instruction that guides the model's behavior, e.g. tone, format, role), temperature, max_tokens, and model. If system_prompt is not set, the default is: You are a helpful assistant. Provide a clear and concise response.

Syntax

aiGenerate(prompt[, params])

Aliases: AIGenerate

Arguments

• prompt — The user prompt or question to send to the model. String
• params — Optional constant Map(String, String) of parameters. Function-specific keys: temperature (sampling temperature controlling randomness; default 0.7), max_tokens (maximum output tokens per call; default 1024), system_prompt (constant system-level instruction guiding the model's behavior; default a generic assistant prompt). The common parameters credentials and model also apply (see AI Functions). Map(String, String)

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('What is 2 + 2? Reply with just the number.')

4

With explicit credentials and system prompt

SELECT aiGenerate('Explain ClickHouse', map('credentials', 'ai_text_credentials', 'system_prompt', 'You are a database expert. Be concise.'))

Summarize column values

SELECT article_title, aiGenerate(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 via the instructions key of the parameter map (e.g. 'keep technical terms untranslated').

Credentials (a named collection specifying the provider, model, endpoint, and optionally an API key) are taken from the credentials key of the optional parameter map, or from the ai_function_text_default_credentials setting when the map omits it.

Syntax

aiTranslate(text, target_language[, params])

Aliases: AITranslate

Arguments

• text — Text to translate. String
• target_language — Target language name or BCP-47 code (e.g. 'French', 'es-MX'). String
• params — Optional constant Map(String, String) of parameters. Function-specific keys: temperature (sampling temperature controlling randomness; default 0.3), max_tokens (maximum output tokens per call; default 1024), instructions (additional style or dialect instructions for the translator). The common parameters credentials and model also apply (see AI Functions). Map(String, String)

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('Hello, world!', 'French')

Bonjour le monde!

Translate to Japanese with style instructions

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