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Implement Sorted Writes #871
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      73ec535
              
                Implement Sorted Writes
              
              
                vinjai 64b8975
              
                Refactored and added more tests for sorting
              
              
                vinjai 76f9894
              
                Added more tests
              
              
                vinjai bd600d6
              
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                vinjai 5029e71
              
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                vinjai 793c99f
              
                Added warning for unsupported Transforms
              
              
                vinjai b6345ba
              
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              | Original file line number | Diff line number | Diff line change | 
|---|---|---|
| @@ -0,0 +1,110 @@ | ||
| # Licensed to the Apache Software Foundation (ASF) under one | ||
| # or more contributor license agreements. See the NOTICE file | ||
| # distributed with this work for additional information | ||
| # regarding copyright ownership. The ASF licenses this file | ||
| # to you under the Apache License, Version 2.0 (the | ||
| # "License"); you may not use this file except in compliance | ||
| # with the License. You may obtain a copy of the License at | ||
| # | ||
| # http://www.apache.org/licenses/LICENSE-2.0 | ||
| # | ||
| # Unless required by applicable law or agreed to in writing, | ||
| # software distributed under the License is distributed on an | ||
| # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| # KIND, either express or implied. See the License for the | ||
| # specific language governing permissions and limitations | ||
| # under the License. | ||
| # pylint:disable=redefined-outer-name | ||
| from typing import List, Tuple | ||
|  | ||
| import pyarrow as pa | ||
|  | ||
| from pyiceberg.table.sorting import NullOrder, SortDirection, SortField | ||
|  | ||
|  | ||
| class PyArrowSortOptions: | ||
| sort_direction: str | ||
| null_order: str | ||
|  | ||
| def __init__(self, sort_direction: str = "ascending", null_order: str = "at_end"): | ||
| if sort_direction not in ("ascending", "descending"): | ||
| raise ValueError('Sort Direction should be one of ["ascending","descending"]') | ||
| if null_order not in ("at_start", "at_end"): | ||
| raise ValueError('Sort Null Order should be one of ["at_start","at_end"]') | ||
|  | ||
| self.sort_direction = sort_direction | ||
| self.null_order = null_order | ||
|  | ||
|  | ||
| def convert_sort_field_to_pyarrow_sort_options(sort_field: SortField) -> PyArrowSortOptions: | ||
| """ | ||
| Convert an Iceberg Table Sort Field to Arrow Sort Options. | ||
|  | ||
| Args: | ||
| sort_field (SortField): Source Iceberg Sort Field to be converted | ||
|  | ||
| Returns: | ||
| PyArrowOptions: PyArrowOptions format for the input Sort Field | ||
| """ | ||
| pyarrow_sort_direction = {SortDirection.ASC: "ascending", SortDirection.DESC: "descending"} | ||
| pyarrow_null_ordering = {NullOrder.NULLS_LAST: "at_end", NullOrder.NULLS_FIRST: "at_start"} | ||
| return PyArrowSortOptions( | ||
| pyarrow_sort_direction.get(sort_field.direction, "ascending"), | ||
| pyarrow_null_ordering.get(sort_field.null_order, "at_end"), | ||
| ) | ||
|  | ||
|  | ||
| def get_sort_indices_arrow_table(arrow_table: pa.Table, sort_seq: List[Tuple[str, PyArrowSortOptions]]) -> List[int]: | ||
| """ | ||
| Return the indices that would sort the input arrow table. | ||
|  | ||
| This function computes an array of indices that define a stable sort of the input arrow_table | ||
|  | ||
| Currently, pyarrow sort_indices function doesn't accept different null ordering across multiple keys | ||
| To make sure, we are able to sort null orders across multiple keys: | ||
| 1. Utilize a stable sort algo (e.g. pyarrow sort indices) | ||
| 2. Sort on the last key first and reverse iterate sort to the first key. | ||
|  | ||
| For instance: | ||
| If the sorting is defined on age asc and then name desc, the sorting can be decomposed into single key stable | ||
| sorts in the following way: | ||
| - first sort by name desc | ||
| - then sort by age asc | ||
|  | ||
| Using a stable sort, we can guarantee that the output would be same across different order keys. | ||
|  | ||
| Pyarrow sort_indices function is stable as mentioned in the doc: https://arrow.apache.org/docs/python/generated/pyarrow.compute.sort_indices.html | ||
|  | ||
| Args: | ||
| arrow_table (pa.Table): Input table to be sorted | ||
| sort_seq: Seq of PyArrowOptions to apply sorting | ||
|  | ||
| Returns: | ||
| List[int]: Indices of the arrow table for sorting | ||
| """ | ||
| import pyarrow as pa | ||
|  | ||
| index_column_name = "__idx__pyarrow_sort__" | ||
| cols = set(arrow_table.column_names) | ||
|  | ||
| while index_column_name in cols: | ||
| index_column_name = f"{index_column_name}_1" | ||
|  | ||
| sorted_table: pa.Table = arrow_table.add_column(0, index_column_name, [list(range(len(arrow_table)))]) | ||
|  | ||
| for col_name, _ in sort_seq: | ||
| if col_name not in cols: | ||
| raise ValueError( | ||
| f"{col_name} not found in arrow table. Expected one of [{','.join([col_name for col_name, _ in cols])}]" | ||
| ) | ||
|  | ||
| for col_name, sort_options in sort_seq[::-1]: | ||
| sorted_table = sorted_table.take( | ||
| # This function works because pyarrow sort_indices function is stable. | ||
| # As mentioned in the docs: https://arrow.apache.org/docs/python/generated/pyarrow.compute.sort_indices.html | ||
| pa.compute.sort_indices( | ||
| sorted_table, sort_keys=[(col_name, sort_options.sort_direction)], null_placement=sort_options.null_order | ||
| ) | ||
| ) | ||
|  | ||
| return sorted_table[index_column_name].to_pylist() | ||
      
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Just wanted to clarify on the separate implementation for sort_indices other than the one provided by pyarrow.
This is because pyarrow sort_indices or Sort Options only supports one order for null placement across keys.
More details here:
While, the iceberg spec doesn't discriminate of having different null ordering across keys: https://iceberg.apache.org/spec/#sort-orders
This function specifically helps to implement the above functionality by sorting across keys and utilizing the stable nature of the sort_indices algo from pyarrow.
We can raise another issue to improve the performance of this function.
In future, if pyarrow sort_indices does support different null ordering across, we can mark this function as obsolete and keep the implementation clean in the iceberg table append and overwrite methods.