t_digest

Category: Probabilistic
Wire type: t_digest
Construction: CREATE

Probabilistic structures provide bounded-memory estimates and membership/frequency queries.

Create a value

Use the top-level CREATE command to initialize this structured value. The example shows its construction options.

amaquet-cli -uri amaquet://127.0.0.1:13378 CREATE '{"key":"example:t_digest","type":"t_digest","options":{"compression":100}}'

Construction options

Example CREATE options: {"compression":100}. Omitted fields use server defaults.

Supported operations

ADD, QUANTILE.

See the complete operation contract for exact arguments, defaults, results, and whether a listed GET is the top-level key command or a type-specific OP. It also identifies read-only operations and documents validation, lazy maintenance, and key-version behavior.

Operation payloads

The following examples use the public amaquet-cli JSON command format. Replace example:t_digest with the key used by your application.

Construction payloads

Use the payload below to initialize this type before issuing reads or type-specific operations.

CREATE

This payload initializes the value and must complete before its type-specific operations are used.

{
  "key": "example:t_digest",
  "type": "t_digest",
  "options": {
    "compression": 100
  }
}

Operations

Each request uses the OP envelope. The response is the type-specific value described in the complete operation contract.

OP ADD

Accepts numeric value, optional weight:1 and returns true; non-positive weights are ignored internally.

{
  "key": "example:t_digest",
  "operation": "ADD",
  "args": {
    "value": 5
  }
}

OP QUANTILE

Accepts numeric q and returns approximate quantile; q clamps to 0…1; empty digest returns JSON-incompatible NaN and therefore should be avoided.

{
  "key": "example:t_digest",
  "operation": "QUANTILE",
  "args": {
    "q": 0.5
  }
}

Top-level read payload

GET reads the current value without changing it:

{
  "key": "example:t_digest"
}

Key lifecycle payloads

These commands apply to the key regardless of its registered type:

• TYPE: {"key":"example:t_digest"} — returns the wire type.
• EXISTS: {"key":"example:t_digest"} — reports whether the key exists.
• EXPIRE: {"key":"example:t_digest","ttl_ms":5000} — assigns a five-second TTL.
• TTL: {"key":"example:t_digest"} — returns the remaining TTL in milliseconds.
• PERSIST: {"key":"example:t_digest"} — removes the TTL.
• DEL: {"keys":["example:t_digest"]} — deletes the key.

For defaults, validation, result shapes, and persistence classification, see the complete operation contract.

Key lifecycle

The key participates in TYPE, EXISTS, TTL, EXPIRE, PERSIST, and DEL. Top-level GET returns the type’s direct public value or a synchronized snapshot.