Function test_decoder_partial

parquet/src/arrow/push_decoder/mod.rs:1012–1048

()

    /// Decode the entire file incrementally, simulating partial reads
    #[test]
    fn test_decoder_partial() {
        let mut decoder = ParquetPushDecoderBuilder::try_new_decoder(test_file_parquet_metadata())
            .unwrap()
            .build()
            .unwrap();

        // First row group, expect a single request for all data needed to read "a" and "b"
        let ranges = expect_needs_data(decoder.try_decode());
        push_ranges_to_decoder(&mut decoder, ranges);

        let batch1 = expect_data(decoder.try_decode());
        let expected1 = TEST_BATCH.slice(0, 200);
        assert_eq!(batch1, expected1);

        // Second row group, this time provide the data in two steps
        let ranges = expect_needs_data(decoder.try_decode());
        let (ranges1, ranges2) = ranges.split_at(ranges.len() / 2);
        assert!(!ranges1.is_empty());
        assert!(!ranges2.is_empty());
        // push first half to simulate partial read
        push_ranges_to_decoder(&mut decoder, ranges1.to_vec());

        // still expect more data
        let ranges = expect_needs_data(decoder.try_decode());
        assert_eq!(ranges, ranges2); // should be the remaining ranges
        // push empty ranges should be a no-op
        push_ranges_to_decoder(&mut decoder, vec![]);
        let ranges = expect_needs_data(decoder.try_decode());
        assert_eq!(ranges, ranges2); // should be the remaining ranges
        push_ranges_to_decoder(&mut decoder, ranges);

        let batch2 = expect_data(decoder.try_decode());
        let expected2 = TEST_BATCH.slice(200, 200);
        assert_eq!(batch2, expected2);

        expect_finished(decoder.try_decode());
    }

    /// Decode multiple columns "a" and "b", expect that the decoder requests
    /// only a single request per row group