Function write_segment_roundtrip

nodedb-columnar/src/writer/segment_writer.rs:326–377

()

    #[test]
    fn write_segment_roundtrip() {
        let schema = analytics_schema();
        let mut mt = ColumnarMemtable::new(&schema);

        for i in 0..100 {
            mt.append_row(&[
                Value::Integer(i),
                Value::String(format!("user_{i}")),
                if i % 3 == 0 {
                    Value::Null
                } else {
                    Value::Float(i as f64 * 0.25)
                },
            ])
            .expect("append");
        }

        let (schema, columns, row_count) = mt.drain();
        let writer = SegmentWriter::plain();
        let segment = writer
            .write_segment(&schema, &columns, row_count, None)
            .expect("write");

        // Verify header.
        let header = SegmentHeader::from_bytes(&segment).expect("valid header");
        assert_eq!(header.magic, *b"NDBS");
        assert_eq!(header.version_major, 1);

        // Verify footer.
        let footer = SegmentFooter::from_segment_tail(&segment).expect("valid footer");
        assert_eq!(footer.column_count, 3);
        assert_eq!(footer.row_count, 100);
        assert_eq!(footer.profile_tag, PROFILE_PLAIN);
        assert_eq!(footer.columns.len(), 3);

        // Verify column metadata.
        assert_eq!(footer.columns[0].name, "id");
        assert_eq!(footer.columns[1].name, "name");
        assert_eq!(footer.columns[2].name, "score");

        // Each column should have 1 block (100 rows < BLOCK_SIZE=1024).
        assert_eq!(footer.columns[0].block_count, 1);
        assert_eq!(footer.columns[0].block_stats[0].row_count, 100);

        // id: min=0, max=99.
        assert_eq!(footer.columns[0].block_stats[0].min, 0.0);
        assert_eq!(footer.columns[0].block_stats[0].max, 99.0);
        assert_eq!(footer.columns[0].block_stats[0].null_count, 0);

        // score: 34 nulls (every 3rd row), min=0.25 (row 1), max=99*0.25=24.75 (row 99).
        assert_eq!(footer.columns[2].block_stats[0].null_count, 34);
    }

    #[test]
    fn write_segment_multi_block() {