KVStore: Refine parallel prehandle snapshot (part-3)

JaySon-Huang commented 3 months ago

What problem does this PR solve?

Issue Number: ref https://github.com/pingcap/tiflash/issues/8081

Problem Summary: In the previous implementation, the code is kind of messy. We will create a SSTFilesToBlockInputStream, then resetSoftLimit a soft limit to the input stream.

What is changed and how it works?

Introduce SnapshotSSTReader to simplify the code. The following methods moved from SSTFilesToBlockInputStream to the new class:
- getApproxBytes
- findSplitKeys
- maybeSkipBySoftLimit
- maybeStopBySoftLimit
- checkFinishedState
Create SnapshotSSTReader with given SoftLimit, then use the "SnapshotSSTReader with soft limit" to create "SSTFilesToBlockInputStream"

struct SnapshotSSTReader
{
    SnapshotSSTReader(
        const SSTViewVec & snaps,
        const TiFlashRaftProxyHelper * proxy_helper,
        RegionID region_id,
        UInt64 snapshot_index,
        const ImutRegionRangePtr & region_range,
        std::optional<SSTScanSoftLimit> && soft_limit,
        const String & log_prefix);

    // Currently it only takes effect if using tablet sst reader which is usually a raftstore v2 case.
    // Otherwise will return zero.
    size_t getApproxBytes() const;
    std::vector<std::string> findSplitKeys(size_t splits_count) const;

    using SSTReaderPtr = std::unique_ptr<SSTReader>;
    SSTReaderPtr write_cf_reader;
    SSTReaderPtr default_cf_reader;
    SSTReaderPtr lock_cf_reader;
};

Check List

Tests

[ ] Unit test
[ ] Integration test
[ ] Manual test (add detailed scripts or steps below)
[ ] No code

Side effects

[ ] Performance regression: Consumes more CPU
[ ] Performance regression: Consumes more Memory
[ ] Breaking backward compatibility

Documentation

[ ] Affects user behaviors
[ ] Contains syntax changes
[ ] Contains variable changes
[ ] Contains experimental features
[ ] Changes MySQL compatibility

Release note

None

ti-chi-bot[bot] commented 3 months ago

[APPROVALNOTIFIER] This PR is NOT APPROVED

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ti-chi-bot[bot] commented 3 months ago

@JaySon-Huang: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-integration-test	dc52cf9e7b4a78c9e005e4476ddf866d75a34f60	link	true	`/test pull-integration-test`

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pingcap / tiflash