Parse a `(columns, rows)` PageRank result into `(node_id, rank)` pairs. The result schema is `node_id` (text) + `rank` (float). `rank` may arrive as a float (native protocol) or as a text-encoded number (pgwire), so both are accepted. An empty result with no columns (empty graph) yields an empty vec; any other column-shape mismatch is a structured error — no silent fallback to wrong data.
(
columns: &[String],
rows: &[Vec<Value>],
)
| 50 | /// vec; any other column-shape mismatch is a structured error — no silent |
| 51 | /// fallback to wrong data. |
| 52 | pub(crate) fn parse_pagerank_rows( |
| 53 | columns: &[String], |
| 54 | rows: &[Vec<Value>], |
| 55 | ) -> NodeDbResult<Vec<(String, f64)>> { |
| 56 | let node_idx = columns.iter().position(|c| c == "node_id"); |
| 57 | let rank_idx = columns.iter().position(|c| c == "rank"); |
| 58 | let (Some(ni), Some(ri)) = (node_idx, rank_idx) else { |
| 59 | if rows.is_empty() { |
| 60 | return Ok(Vec::new()); |
| 61 | } |
| 62 | return Err(NodeDbError::storage(format!( |
| 63 | "unexpected pagerank columns: {columns:?} (expected [node_id, rank])" |
| 64 | ))); |
| 65 | }; |
| 66 | |
| 67 | let mut out = Vec::with_capacity(rows.len()); |
| 68 | for row in rows { |
| 69 | let node = row |
| 70 | .get(ni) |
| 71 | .and_then(|v| v.as_str()) |
| 72 | .ok_or_else(|| NodeDbError::storage("pagerank row missing node_id"))? |
| 73 | .to_string(); |
| 74 | let rank = row |
| 75 | .get(ri) |
| 76 | .and_then(value_as_f64) |
| 77 | .ok_or_else(|| NodeDbError::storage("pagerank row missing or non-numeric rank"))?; |
| 78 | out.push((node, rank)); |
| 79 | } |
| 80 | Ok(out) |
| 81 | } |
| 82 | |
| 83 | /// Coerce a result cell to `f64`, accepting either a native numeric value or a |
| 84 | /// text-encoded number (the pgwire transport renders floats as text). |