query/optimizer/
windowed_sort.rs

// Copyright 2023 Greptime Team
//
// Licensed 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.

use std::collections::HashSet;
use std::sync::Arc;

use datafusion::physical_optimizer::PhysicalOptimizerRule;
use datafusion::physical_plan::coalesce_batches::CoalesceBatchesExec;
use datafusion::physical_plan::coalesce_partitions::CoalescePartitionsExec;
use datafusion::physical_plan::filter::FilterExec;
use datafusion::physical_plan::projection::ProjectionExec;
use datafusion::physical_plan::repartition::RepartitionExec;
use datafusion::physical_plan::sorts::sort::SortExec;
use datafusion::physical_plan::sorts::sort_preserving_merge::SortPreservingMergeExec;
use datafusion::physical_plan::ExecutionPlan;
use datafusion_common::tree_node::{Transformed, TreeNode};
use datafusion_common::Result as DataFusionResult;
use datafusion_physical_expr::expressions::Column as PhysicalColumn;
use datafusion_physical_expr::LexOrdering;
use store_api::region_engine::PartitionRange;
use table::table::scan::RegionScanExec;

use crate::part_sort::PartSortExec;
use crate::window_sort::WindowedSortExec;

/// Optimize rule for windowed sort.
///
/// This is expected to run after [`ScanHint`] and [`ParallelizeScan`].
/// It would change the original sort to a custom plan. To make sure
/// other rules are applied correctly, this rule can be run as later as
/// possible.
///
/// [`ScanHint`]: crate::optimizer::scan_hint::ScanHintRule
/// [`ParallelizeScan`]: crate::optimizer::parallelize_scan::ParallelizeScan
#[derive(Debug)]
pub struct WindowedSortPhysicalRule;

impl PhysicalOptimizerRule for WindowedSortPhysicalRule {
    fn optimize(
        &self,
        plan: Arc<dyn ExecutionPlan>,
        config: &datafusion::config::ConfigOptions,
    ) -> DataFusionResult<Arc<dyn ExecutionPlan>> {
        Self::do_optimize(plan, config)
    }

    fn name(&self) -> &str {
        "WindowedSortRule"
    }

    fn schema_check(&self) -> bool {
        false
    }
}

impl WindowedSortPhysicalRule {
    fn do_optimize(
        plan: Arc<dyn ExecutionPlan>,
        _config: &datafusion::config::ConfigOptions,
    ) -> DataFusionResult<Arc<dyn ExecutionPlan>> {
        let result = plan
            .transform_down(|plan| {
                if let Some(sort_exec) = plan.as_any().downcast_ref::<SortExec>() {
                    // TODO: support multiple expr in windowed sort
                    if sort_exec.expr().len() != 1 {
                        return Ok(Transformed::no(plan));
                    }

                    let preserve_partitioning = sort_exec.preserve_partitioning();

                    let sort_input = remove_repartition(sort_exec.input().clone())?.data;
                    // Gets scanner info from the input without repartition before filter.
                    let Some(scanner_info) = fetch_partition_range(sort_input.clone())? else {
                        return Ok(Transformed::no(plan));
                    };

                    if let Some(first_sort_expr) = sort_exec.expr().first()
                        && let Some(column_expr) = first_sort_expr
                            .expr
                            .as_any()
                            .downcast_ref::<PhysicalColumn>()
                        && scanner_info.time_index.contains(column_expr.name())
                    {
                    } else {
                        return Ok(Transformed::no(plan));
                    }
                    let first_sort_expr = sort_exec.expr().first().unwrap().clone();

                    // PartSortExec is unnecessary if:
                    // - there is no tag column, and
                    // - the sort is ascending on the time index column
                    let new_input = if scanner_info.tag_columns.is_empty()
                        && !first_sort_expr.options.descending
                    {
                        sort_input
                    } else {
                        Arc::new(PartSortExec::new(
                            first_sort_expr.clone(),
                            sort_exec.fetch(),
                            scanner_info.partition_ranges.clone(),
                            sort_input,
                        ))
                    };

                    let windowed_sort_exec = WindowedSortExec::try_new(
                        first_sort_expr,
                        sort_exec.fetch(),
                        scanner_info.partition_ranges,
                        new_input,
                    )?;

                    if !preserve_partitioning {
                        let order_preserving_merge = SortPreservingMergeExec::new(
                            LexOrdering::new(sort_exec.expr().to_vec()),
                            Arc::new(windowed_sort_exec),
                        );
                        return Ok(Transformed {
                            data: Arc::new(order_preserving_merge),
                            transformed: true,
                            tnr: datafusion_common::tree_node::TreeNodeRecursion::Stop,
                        });
                    } else {
                        return Ok(Transformed {
                            data: Arc::new(windowed_sort_exec),
                            transformed: true,
                            tnr: datafusion_common::tree_node::TreeNodeRecursion::Stop,
                        });
                    }
                }

                Ok(Transformed::no(plan))
            })?
            .data;

        Ok(result)
    }
}

#[derive(Debug)]
struct ScannerInfo {
    partition_ranges: Vec<Vec<PartitionRange>>,
    time_index: HashSet<String>,
    tag_columns: Vec<String>,
}

fn fetch_partition_range(input: Arc<dyn ExecutionPlan>) -> DataFusionResult<Option<ScannerInfo>> {
    let mut partition_ranges = None;
    let mut time_index = HashSet::new();
    let mut tag_columns = None;
    let mut is_batch_coalesced = false;

    input.transform_up(|plan| {
        // Unappliable case, reset the state.
        if plan.as_any().is::<RepartitionExec>()
            || plan.as_any().is::<CoalescePartitionsExec>()
            || plan.as_any().is::<SortExec>()
            || plan.as_any().is::<WindowedSortExec>()
        {
            partition_ranges = None;
        }

        if plan.as_any().is::<CoalesceBatchesExec>() {
            is_batch_coalesced = true;
        }

        // Collects alias of the time index column.
        if let Some(projection) = plan.as_any().downcast_ref::<ProjectionExec>() {
            for (expr, output_name) in projection.expr() {
                if let Some(column_expr) = expr.as_any().downcast_ref::<PhysicalColumn>() {
                    if time_index.contains(column_expr.name()) {
                        time_index.insert(output_name.clone());
                    }
                }
            }
        }

        if let Some(region_scan_exec) = plan.as_any().downcast_ref::<RegionScanExec>() {
            partition_ranges = Some(region_scan_exec.get_uncollapsed_partition_ranges());
            // Reset time index column.
            time_index = HashSet::from([region_scan_exec.time_index()]);
            tag_columns = Some(region_scan_exec.tag_columns());

            // set distinguish_partition_ranges to true, this is an incorrect workaround
            if !is_batch_coalesced {
                region_scan_exec.with_distinguish_partition_range(true);
            }
        }

        Ok(Transformed::no(plan))
    })?;

    let result = try {
        ScannerInfo {
            partition_ranges: partition_ranges?,
            time_index,
            tag_columns: tag_columns?,
        }
    };

    Ok(result)
}

/// Removes the repartition plan between the filter and region scan.
fn remove_repartition(
    plan: Arc<dyn ExecutionPlan>,
) -> DataFusionResult<Transformed<Arc<dyn ExecutionPlan>>> {
    plan.transform_down(|plan| {
        if plan.as_any().is::<FilterExec>() {
            // Checks child.
            let maybe_repartition = plan.children()[0];
            if maybe_repartition.as_any().is::<RepartitionExec>() {
                let maybe_scan = maybe_repartition.children()[0];
                if maybe_scan.as_any().is::<RegionScanExec>() {
                    let new_filter = plan.clone().with_new_children(vec![maybe_scan.clone()])?;
                    return Ok(Transformed::yes(new_filter));
                }
            }
        }

        Ok(Transformed::no(plan))
    })
}
query/optimizer/windowed_sort.rs

query/optimizer/
windowed_sort.rs
