feat: unordered scanner scans data by time ranges

[evenyag]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

What's changed and what's your intention?

This PR adds the initial implementation for the unordered scanner to support reading rows from time ranges individually.

The scanner groups sources (files and memtables) into ranges and maintains a RangeMeta to store the metadata of that range. Each PartitionRange refers to a RangeMeta in the StreamContext so we can use the PartitionRange::identifier to locate the RangeMeta.

SeqScan and UnorderedScan have different grouping strategies:

• SeqScan merges all overlapping files and memtables to ensure output rows are sorted. So it puts overlapping files and memtables in the same range.
  • If the range only consists of one source, then it can further split row groups of the source into multiple ranges
• UnorderedScan can assign each row group to a dedicated range as it doesn't sort and merge duplication rows

The implementations of grouping strategies are similar to SeqDistributor and UnorderedDistributor.

It also refactors the scan_partition() method by wrapping some methods to scan memtables and files.

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR requires documentation updates.

Summary by CodeRabbit

Release Notes

• New Features

  • Introduced a new module for managing partition ranges, enhancing data scanning capabilities.
  • Added methods to handle pruning of memtable and file ranges, improving efficiency during scans.

• Improvements

  • Updated return types for several methods to utilize BTreeMap, enhancing data organization and access.
  • Enhanced internal state management with the addition of num_ranges to track range counts.

• Bug Fixes

  • Removed unnecessary code attributes to streamline the codebase.

• Documentation

  • Added comments for future development tasks to improve code maintainability.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Walkthrough

The changes introduce a new field num_ranges to the MemtableStats struct and modify the return types of various methods in the Memtable trait from Vec<MemtableRange> to BTreeMap<usize, MemtableRange>. This shift alters how ranges are represented and accessed across multiple implementations, including BulkMemtable, PartitionTreeMemtable, TimeSeriesMemtable, and EmptyMemtable. Additionally, a new module for managing partition ranges is added, along with various utility functions for efficient data scanning operations.

Changes

File Path	Change Summary
src/mito2/src/memtable.rs	Added num_ranges field to MemtableStats, updated ranges method to return BTreeMap<usize, MemtableRange>.
src/mito2/src/memtable/bulk.rs	Updated method return type from Vec<MemtableRange> to BTreeMap<usize, MemtableRange>.
src/mito2/src/memtable/partition_tree.rs	Updated method return type from Vec<MemtableRange> to BTreeMap<usize, MemtableRange>, added num_ranges field to MemtableRange.
src/mito2/src/memtable/time_series.rs	Updated method return type from Vec<MemtableRange> to BTreeMap<usize, MemtableRange>, added num_ranges field to MemtableRange.
src/mito2/src/read.rs	Added new module range.
src/mito2/src/read/dedup.rs	Removed #[allow(dead_code)] attribute from new function in LastNonNull.
src/mito2/src/read/range.rs	Introduced RowGroupIndex and RangeMeta structs; added methods for managing partition ranges.
src/mito2/src/read/scan_region.rs	Added prune_memtable and prune_file methods, updated StreamContext to include new fields for managing ranges.
src/mito2/src/read/seq_scan.rs	Updated SeqScan::new method to initialize StreamContext differently; modified ScanPart structure.
src/mito2/src/read/unordered_scan.rs	Removed UnorderedDistributor, refactored scanning logic into direct methods for handling partition ranges.
src/mito2/src/sst/parquet.rs	Changed visibility of DEFAULT_ROW_GROUP_SIZE from private to public within the crate.
src/mito2/src/sst/parquet/reader.rs	Added a comment in ParquetReaderBuilder for future task tracking.
src/mito2/src/test_util/memtable_util.rs	Updated get_ranges method return type from Vec<MemtableRange> to BTreeMap<usize, MemtableRange>.

Possibly related PRs

• feat: migrate local WAL regions #4715: Modifications to the handling of Write-Ahead Logging (WAL) regions, potentially related to the changes in range representation and access.

Suggested reviewers

• v0y4g3r
• waynexia
• MichaelScofield
• WenyXu

Poem

In the meadow where bunnies play,
New ranges hop in a bright array.
With maps of trees, our data's neat,
Each hop and skip, a joyful feat!
So let's rejoice, with ears held high,
For memtables now reach for the sky! 🐇✨

---

Thank you for using CodeRabbit. We offer it for free to the OSS community and would appreciate your support in helping us grow. If you find it useful, would you consider giving us a shout-out on your favorite social media?

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

🪧 Tips

Chat

There are 3 ways to chat with CodeRabbit:

• Review comments: Directly reply to a review comment made by CodeRabbit. Example:
  • I pushed a fix in commit <commit_id>, please review it.
  • Generate unit testing code for this file.
  • Open a follow-up GitHub issue for this discussion.
• Files and specific lines of code (under the "Files changed" tab): Tag @coderabbitai in a new review comment at the desired location with your query. Examples:
  • @coderabbitai generate unit testing code for this file.
  • @coderabbitai modularize this function.
• PR comments: Tag @coderabbitai in a new PR comment to ask questions about the PR branch. For the best results, please provide a very specific query, as very limited context is provided in this mode. Examples:
  • @coderabbitai gather interesting stats about this repository and render them as a table. Additionally, render a pie chart showing the language distribution in the codebase.
  • @coderabbitai read src/utils.ts and generate unit testing code.
  • @coderabbitai read the files in the src/scheduler package and generate a class diagram using mermaid and a README in the markdown format.
  • @coderabbitai help me debug CodeRabbit configuration file.

Note: Be mindful of the bot's finite context window. It's strongly recommended to break down tasks such as reading entire modules into smaller chunks. For a focused discussion, use review comments to chat about specific files and their changes, instead of using the PR comments.

CodeRabbit Commands (Invoked using PR comments)

• @coderabbitai pause to pause the reviews on a PR.
• @coderabbitai resume to resume the paused reviews.
• @coderabbitai review to trigger an incremental review. This is useful when automatic reviews are disabled for the repository.
• @coderabbitai full review to do a full review from scratch and review all the files again.
• @coderabbitai summary to regenerate the summary of the PR.
• @coderabbitai resolve resolve all the CodeRabbit review comments.
• @coderabbitai configuration to show the current CodeRabbit configuration for the repository.
• @coderabbitai help to get help.

Other keywords and placeholders

• Add @coderabbitai ignore anywhere in the PR description to prevent this PR from being reviewed.
• Add @coderabbitai summary to generate the high-level summary at a specific location in the PR description.
• Add @coderabbitai anywhere in the PR title to generate the title automatically.

Documentation and Community

• Visit our Documentation for detailed information on how to use CodeRabbit.
• Join our Discord Community to get help, request features, and share feedback.
• Follow us on X/Twitter for updates and announcements.

[evenyag]

@coderabbitai summary

[coderabbitai]

Actions performed

Summary regeneration triggered.

[codecov]

Codecov Report

Attention: Patch coverage is 84.17085% with 63 lines in your changes missing coverage. Please review.

Project coverage is 84.28%. Comparing base (0f99218) to head (3d419fc).
Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4757      +/-   ##
==========================================
- Coverage   84.56%   84.28%   -0.28%     
==========================================
  Files        1118     1118              
  Lines      202889   202925      +36     
==========================================
- Hits       171566   171033     -533     
- Misses      31323    31892     +569     

[WenyXu]

LGTM