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avoid performance jitter caused by statistics feedback #17478

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eurekaka opened this issue May 28, 2020 · 0 comments · Fixed by #15503
Closed

avoid performance jitter caused by statistics feedback #17478

eurekaka opened this issue May 28, 2020 · 0 comments · Fixed by #15503
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component/statistics epic/query-feedback-GA type/enhancement The issue or PR belongs to an enhancement.

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Statistics feedback would impose periodical read/write burden on the database. Each TiDB would dump the feedbacks collected on this instance into TiKV every 10 mins, and the stats owner TiDB instance would read the feedbacks dumped every 15 seconds. If the stats owner TiDB finds there are new feedbacks from TiKV, it would merge the feedbacks with statistics in cache, then dump all these updated statistics into TiKV. This dump operation is pretty heavy if there are bunches of feedbacks on bunches of columns/indexes, since it can be treated as a light-weight ANALYZE on a lot of tables.
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component/statistics epic/query-feedback-GA type/enhancement The issue or PR belongs to an enhancement.
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statistics: ease the impact of stats feedback on cluster eurekaka/tidb
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@SunRunAway @eurekaka