Method scan

src/persist/src/postgres.rs:623–654

(
        &self,
        key: &str,
        from: SeqNo,
        limit: usize,
    )

    }

    async fn scan(
        &self,
        key: &str,
        from: SeqNo,
        limit: usize,
    ) -> Result<Vec<VersionedData>, ExternalError> {
        let q = "SELECT sequence_number, data FROM consensus
             WHERE shard = $1 AND sequence_number >= $2
             ORDER BY sequence_number ASC LIMIT $3";
        let Ok(limit) = i64::try_from(limit) else {
            return Err(ExternalError::from(anyhow!(
                "limit must be [0, i64::MAX]. was: {:?}",
                limit
            )));
        };
        let rows = {
            let client = self.get_connection().await?;
            let statement = client.prepare_cached(q).await?;
            pg_query_prepared(&client, &statement, &[&key, &from, &limit]).await?
        };
        let mut results = Vec::with_capacity(rows.len());

        for row in rows {
            let seqno: SeqNo = row.try_get("sequence_number")?;
            let data: Vec<u8> = row.try_get("data")?;
            results.push(VersionedData {
                seqno,
                data: Bytes::from(data),
            });
        }
        Ok(results)
    }

    async fn truncate(&self, key: &str, seqno: SeqNo) -> Result<Option<usize>, ExternalError> {
        // `sequence_number >= 0` keeps the seqno -1 sentinel (see `compare_and_set`); it is a no-op