Support List and LargeList in Row format (#3159) #3251
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| /// | ||
| /// ```text | ||
| /// ┌──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┐ | ||
| /// [1_u8, 2_u8, 3_u8] │01│01│01│02│01│03│00│00│00│02│00│00│00│02│00│00│00│02│00│00│00│03│ |
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I get the │01│01│01│02│01│03│ prefix and the │00│00│00│03│ suffix. But where do the other bytes come from?
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the lengths of each encoded row, and the number of elements
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So basically 00│00│00│02│00│00│00│02│00│00│00│02│00│00│00│03 represents [element0_len, element1_len, element2_len, element count] --> [2, 2, 2, 3]
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maybe we can add this explanation to the docstring?
Co-authored-by: Marco Neumann <[email protected]>
| /// | ||
| /// ```text | ||
| /// ┌──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┬──┐ | ||
| /// [1_u8, 2_u8, 3_u8] │01│01│01│02│01│03│00│00│00│02│00│00│00│02│00│00│00│02│00│00│00│03│ |
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So basically 00│00│00│02│00│00│00│02│00│00│00│02│00│00│00│03 represents [element0_len, element1_len, element2_len, element count] --> [2, 2, 2, 3]
| != sort_field.options.descending, | ||
| }; | ||
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| let field = SortField::new_with_options(f.data_type().clone(), options); |
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I don't understand how descending sort is achieved if the list is always encoded descending false 🤔 )
However, I see it is tested below, so 👍
let options = SortOptions {
descending: true,
nulls_first: false,
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Only the elements are encoded with descending false, they are then encoded using variable length encoding which may reorder them. Yes it is mind-bending 😅
| builder.values().append_value(32); | ||
| builder.values().append_value(52); | ||
| builder.append(true); | ||
| builder.values().append_value(32); // MASKED |
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masked means this row is NULL so these values should be igored
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| assert!(rows.row(0) < rows.row(1)); // [32, 52, 32] < [32, 52, 12] | ||
| assert!(rows.row(2) > rows.row(1)); // [32, 42] > [32, 52, 12] | ||
| assert!(rows.row(3) < rows.row(2)); // null < [32, 42] |
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👍
Thank you for the comments -- they make the tests easy to follow
| // ] | ||
| let options = SortOptions { | ||
| descending: false, | ||
| nulls_first: true, |
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I recommend adding a test in nested lists for nulls_first: false, and verify that
assert!(rows.row(0) < rows.row(1));
Co-authored-by: Andrew Lamb <[email protected]>
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Benchmark runs are scheduled for baseline = de3828c and contender = 9833288. 9833288 is a master commit associated with this PR. Results will be available as each benchmark for each run completes. |
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I can feel DataFusion grouping getting faster.....
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Which issue does this PR close?
Part of #3159
Rationale for this change
The longer term goal is to make the Row Format support enough types to use in DataFusion so we can use it for a unified GroupBy operation
What changes are included in this PR?
Add support for encoding/decoding lists from the row format
Are there any user-facing changes?