Add new items in scan context

[hongyunyan]

What problem does this PR solve?

Issue Number: ref #5926

Problem Summary:

What is changed and how it works?

Add more information in Scan Context:

1. time cost of wait index
2. read size from s3 and cache

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

[JaySon-Huang]

And there are some ColumnFile in the DeltaValueSpace read from local cache or fetch from remote write nodes. We should add them to total_disagg_read_cache_hit_size/total_disagg_read_cache_miss_size

tiflash/dbms/src/Storages/DeltaMerge/Remote/RNWorkerFetchPages.cpp

Lines 41 to 71 in 96fbffd

	RNLocalPageCache::OccupySpaceResult blockingOccupySpaceForTask(const RNReadSegmentTaskPtr & seg_task)
	{
	std::vector<PageOID> cf_tiny_oids;
	{
	cf_tiny_oids.reserve(seg_task->meta.delta_tinycf_page_ids.size());
	for (const auto & page_id : seg_task->meta.delta_tinycf_page_ids)
	{
	auto page_oid = PageOID{
	.store_id = seg_task->meta.store_id,
	.ks_table_id = {seg_task->meta.keyspace_id, seg_task->meta.physical_table_id},
	.page_id = page_id,
	};
	cf_tiny_oids.emplace_back(page_oid);
	}
	}
	// Note: We must occupySpace segment by segment, because we need to read
	// at least the complete data of one segment in order to drive everything forward.
	// Currently we call occupySpace for each FetchPagesRequest, which is fine,
	// because we send one request each seg_task. If we want to split
	// FetchPagesRequest into multiples in future, then we need to change
	// the moment of calling `occupySpace`.
	auto page_cache = seg_task->meta.dm_context->db_context.getSharedContextDisagg()->rn_page_cache;
	Stopwatch w_occupy;
	auto occupy_result = page_cache->occupySpace(cf_tiny_oids, seg_task->meta.delta_tinycf_page_sizes);
	// This metric is per-segment.
	GET_METRIC(tiflash_disaggregated_breakdown_duration_seconds, type_cache_occupy).Observe(w_occupy.elapsedSeconds());
	return occupy_result;
	}

[Lloyd-Pottiger]

rename to total_dmfile_rough_set_index_check_time_ns ?

[JaySon-Huang]

yes, we can distinguish the loading time and checking time of rough set index

[hongyunyan]

Does this mean that we need to use two indicators separately for statistics?

[Lloyd-Pottiger]

I think the sum is enough.

[JaySon-Huang]

The rest LGTM

[hongyunyan]

/run-all-tests

[JaySon-Huang]

/run-all-tests

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JaySon-Huang, Lloyd-Pottiger

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-02 09:03:50.404491048 +0000 UTC m=+262514.346839579: ☑️ agreed by JaySon-Huang.
• 2023-08-02 09:06:07.469104072 +0000 UTC m=+262651.411452603: ☑️ agreed by Lloyd-Pottiger.

[hongyunyan]

/run-all-tests

[hongyunyan]

/run-all-tests

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