Constant SELECT_SQL 

pub const SELECT_SQL: &str = r#"
SELECT
    thread_id,
    checkpoint,
    checkpoint_ns,
    checkpoint_id,
    parent_checkpoint_id,
    metadata,
    (
        SELECT array_agg(array[bl.channel::bytea, bl.type::bytea, bl.blob])
        FROM jsonb_each_text(checkpoint -> 'channel_versions')
        INNER JOIN checkpoint_blobs bl
            ON bl.thread_id = checkpoints.thread_id
            AND bl.checkpoint_ns = checkpoints.checkpoint_ns
            AND bl.channel = jsonb_each_text.key
            AND bl.version = jsonb_each_text.value
    ) AS channel_values,
    (
        SELECT array_agg(array[cw.task_id::text::bytea, cw.channel::bytea, cw.type::bytea, cw.blob] ORDER BY cw.task_id, cw.idx)
        FROM checkpoint_writes cw
        WHERE cw.thread_id = checkpoints.thread_id
            AND cw.checkpoint_ns = checkpoints.checkpoint_ns
            AND cw.checkpoint_id = checkpoints.checkpoint_id
    ) AS pending_writes
FROM checkpoints
"#;

Select a checkpoint with its channel values and pending writes.