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observe

Schedules one keyed READ at both the pre and terminal execution checkpoints.

Scalar function Program CompilerSimulate

Example

Runs locally

-- Schedule a storage observation on a runnable candidate
WITH actors AS (
  SELECT
    '0x1000000000000000000000000000000000000001'::ADDRESS AS sender,
    '0x2000000000000000000000000000000000000002'::ADDRESS AS writer
),
runnable_candidate AS (
  SELECT
    'pass'::VARCHAR AS candidate_key,
    program([execute_call(
      sender,
      writer,
      '0x000000000000000000000000000000000000000000000000000000000000002a'::BYTES,
      1::UINT256,
      100000::UBIGINT
    )]) AS program,
    [observe('writer.slot.checkpoint'::VARCHAR, storage_at(writer, '0x0000000000000000000000000000000000000000000000000000000000000000'::BYTES32))] AS observations
  FROM actors
)
SELECT
  candidate_key,
  len(observations)::INTEGER AS scheduled_observations,
  observations[1] IS NOT NULL AS scheduled
FROM runnable_candidate;
-- => [{"candidate_key":"pass","scheduled_observations":1,"scheduled":"true"}]

API reference

observe(VARCHAR, READ) #

Schedules one keyed READ at both the pre and terminal execution checkpoints.

Inputs

Name Type Use
observation_key VARCHAR

Non-NULL valid UTF-8 key; the consumed request requires 1-256 bytes and no NUL byte.

 required positional
read READ

Non-NULL READ evaluated once before step zero and once at terminal state.

 required positional

Returns

Name Type
observation OBSERVATION

Pre-and-terminal OBSERVATION. Returns one OBSERVATION that expands to two points, pre and terminal, when execution requests are compiled.

observe(VARCHAR, READ, VARCHAR) #

Schedules one keyed READ at exactly the pre or terminal execution checkpoint.

Inputs

Name Type Use
observation_key VARCHAR

Non-NULL valid UTF-8 key; the consumed request requires 1-256 bytes and no NUL byte.

 required positional
read READ

Non-NULL READ evaluated at the selected checkpoint.

 required positional
checkpoint VARCHAR

Case-insensitive selector; only pre or terminal is accepted.

 required positional

Returns

Name Type
observation OBSERVATION

Single-checkpoint OBSERVATION. Returns one OBSERVATION that expands to the selected pre or terminal point.

Guidance

Request validation

Key length, NUL bytes, and duplicate points are validated when the observation list is consumed. A request may contain at most 256 expanded points across all OBSERVATION values.

Examples

Runs locally

-- Schedule a storage observation on a runnable candidate
WITH actors AS (
  SELECT
    '0x1000000000000000000000000000000000000001'::ADDRESS AS sender,
    '0x2000000000000000000000000000000000000002'::ADDRESS AS writer
),
runnable_candidate AS (
  SELECT
    'pass'::VARCHAR AS candidate_key,
    program([execute_call(
      sender,
      writer,
      '0x000000000000000000000000000000000000000000000000000000000000002a'::BYTES,
      1::UINT256,
      100000::UBIGINT
    )]) AS program,
    [observe('writer.slot.checkpoint'::VARCHAR, storage_at(writer, '0x0000000000000000000000000000000000000000000000000000000000000000'::BYTES32), 'pre'::VARCHAR)] AS observations
  FROM actors
)
SELECT
  candidate_key,
  len(observations)::INTEGER AS scheduled_observations,
  observations[1] IS NOT NULL AS scheduled
FROM runnable_candidate;
-- => [{"candidate_key":"pass","scheduled_observations":1,"scheduled":"true"}]