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This topic has been translated from a Chinese forum by GPT and might contain errors.
Original topic: 用TiDB Lightning 把v5.4.1数据导入v6.5.3集群，执行计划不一致
[TiDB Usage Environment] Production Environment
[TiDB Version] v6.5.3
[Reproduction Path] Importing v5.4.1 data into v6.5.3 cluster using TiDB Lightning
[Encountered Problem: Phenomenon and Impact]
The table structure is the same, but the execution plan query has turned into a full table scan.
Found that a table’s query IndexRangeScan has turned into IndexFullScan global scan
[Resource Configuration] Go to TiDB Dashboard - Cluster Info - Hosts and take a screenshot of this page
[Attachments: Screenshots/Logs/Monitoring]
Recollect the statistics of the table on 6.5. Seeing the above keyword, all indicate that the statistics are inaccurate.
Execution plan after statistics
One is from July, and the other is from June.
There is a significant difference in the amount of data based on the conditions.
July has only over 10,000, while June has nearly 3 million.
The main table, r, has always been using IndexRangeScan.
The other smaller sub-tables will choose between IndexRangeScan or IndexFullScan based on the amount of data returned by the main table. I don’t think there’s a big issue.
Changed to the June version.
Sorry, I made a mistake earlier. The statistics for your version 5.4 are also inaccurate. For table O, you need to collect statistics.
All changed to June, re-statistics were done, and the data was migrated from v5.4.1.
It was imported through a tool, so it should be necessary to manually or automatically collect the statistics once. The statistics information should not be imported as well.
I don’t know if the optimizer has made improvements or something, but the way the tables are joined and the execution order are different now.
@Kongdom @胡杨树旁 The v6.5.3 here is executed after manual statistics.
5.4.1 needs to execute quickly.
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