{"action":"created","issue":{"url":"https://api.github.com/repos/pingcap/tikv/issues/3290","repository_url":"https://api.github.com/repos/pingcap/tikv","labels_url":"https://api.github.com/repos/pingcap/tikv/issues/3290/labels{/name}","comments_url":"https://api.github.com/repos/pingcap/tikv/issues/3290/comments","events_url":"https://api.github.com/repos/pingcap/tikv/issues/3290/events","html_url":"https://github.com/pingcap/tikv/pull/3290","id":339297504,"node_id":"MDExOlB1bGxSZXF1ZXN0MTk5OTg2MjI2","number":3290,"title":"Txn: collapse continuous rollbacks","user":{"login":"zhangjinpeng1987","id":19700528,"node_id":"MDQ6VXNlcjE5NzAwNTI4","avatar_url":"https://avatars2.githubusercontent.com/u/19700528?v=4","gravatar_id":"","url":"https://api.github.com/users/zhangjinpeng1987","html_url":"https://github.com/zhangjinpeng1987","followers_url":"https://api.github.com/users/zhangjinpeng1987/followers","following_url":"https://api.github.com/users/zhangjinpeng1987/following{/other_user}","gists_url":"https://api.github.com/users/zhangjinpeng1987/gists{/gist_id}","starred_url":"https://api.github.com/users/zhangjinpeng1987/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/zhangjinpeng1987/subscriptions","organizations_url":"https://api.github.com/users/zhangjinpeng1987/orgs","repos_url":"https://api.github.com/users/zhangjinpeng1987/repos","events_url":"https://api.github.com/users/zhangjinpeng1987/events{/privacy}","received_events_url":"https://api.github.com/users/zhangjinpeng1987/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":2,"created_at":"2018-07-09T04:00:02Z","updated_at":"2018-07-16T05:37:50Z","closed_at":null,"author_association":"CONTRIBUTOR","pull_request":{"url":"https://api.github.com/repos/pingcap/tikv/pulls/3290","html_url":"https://github.com/pingcap/tikv/pull/3290","diff_url":"https://github.com/pingcap/tikv/pull/3290.diff","patch_url":"https://github.com/pingcap/tikv/pull/3290.patch"},"body":"\r\n## What have you changed? (mandatory)\r\n\r\nPreviously, when a key rollbacked for several times, there will be several rollbacks in `write` column family. These rollbacks only wiped by GC system, so reading the key will be slow before GC wipe these rollbacks. ref to https://github.com/pingcap/tikv/pull/2834\r\n\r\nThis PR collapse continuous rollbacks, and only keep the latest rollback. This optimization works because `PreWrite` is not allowed when there exists a commit version whose commit timestamp is larger than or equal to `PreWrite`'s start timestamp, even if the commit type is rollback.\r\n\r\n## What are the type of the changes? (mandatory)\r\n\r\n- Improvement\r\n\r\n## How has this PR been tested? (mandatory)\r\n\r\nUnit test and CI\r\n\r\n## Does this PR affect documentation (docs/docs-cn) update? (mandatory)\r\n\r\nNo\r\n\r\n## Does this PR affect tidb-ansible update? (mandatory)\r\n\r\nNo\r\n\r\n## Refer to a related PR or issue link (optional)\r\n\r\nhttps://github.com/pingcap/tikv/pull/2834\r\n"},"comment":{"url":"https://api.github.com/repos/pingcap/tikv/issues/comments/405152957","html_url":"https://github.com/pingcap/tikv/pull/3290#issuecomment-405152957","issue_url":"https://api.github.com/repos/pingcap/tikv/issues/3290","id":405152957,"node_id":"MDEyOklzc3VlQ29tbWVudDQwNTE1Mjk1Nw==","user":{"login":"disksing","id":12077877,"node_id":"MDQ6VXNlcjEyMDc3ODc3","avatar_url":"https://avatars1.githubusercontent.com/u/12077877?v=4","gravatar_id":"","url":"https://api.github.com/users/disksing","html_url":"https://github.com/disksing","followers_url":"https://api.github.com/users/disksing/followers","following_url":"https://api.github.com/users/disksing/following{/other_user}","gists_url":"https://api.github.com/users/disksing/gists{/gist_id}","starred_url":"https://api.github.com/users/disksing/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/disksing/subscriptions","organizations_url":"https://api.github.com/users/disksing/orgs","repos_url":"https://api.github.com/users/disksing/repos","events_url":"https://api.github.com/users/disksing/events{/privacy}","received_events_url":"https://api.github.com/users/disksing/received_events","type":"User","site_admin":false},"created_at":"2018-07-16T05:37:50Z","updated_at":"2018-07-16T05:37:50Z","author_association":"MEMBER","body":"LGTM"}}
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