Method insert_if_absent

nodedb-columnar/src/mutation/write.rs:122–147

`INSERT ... ON CONFLICT DO NOTHING` semantics: append only if the PK is absent; silently skip on duplicate. Returns `Ok(MutationResult { wal_records })` with an empty vector when the row was skipped, so callers that batch WAL appends can detect no-ops by checking `wal_records.is_empty()`.

(&mut self, values: &[Value])

    /// when the row was skipped, so callers that batch WAL appends can
    /// detect no-ops by checking `wal_records.is_empty()`.
    pub fn insert_if_absent(&mut self, values: &[Value]) -> Result<MutationResult, ColumnarError> {
        let pk_bytes = self.extract_pk_bytes(values)?;
        if self.pk_index.contains(&pk_bytes) {
            return Ok(MutationResult {
                wal_records: Vec::new(),
            });
        }

        let row_data = encode_row_for_wal(values)?;
        let wal = ColumnarWalRecord::InsertRow {
            collection: self.collection.clone(),
            row_data,
        };
        self.memtable.append_row(values)?;
        let location = RowLocation {
            segment_id: self.memtable_segment_id,
            row_index: self.memtable_row_counter,
        };
        self.pk_index.upsert(pk_bytes, location);
        self.memtable_surrogates.push(None);
        self.memtable_row_counter += 1;

        Ok(MutationResult {
            wal_records: vec![wal],
        })
    }

    /// Look up the current row for a PK in the memtable, if present.
    ///