docs/design: add design doc for index usage information #20316
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| Because the max length of schema name, table name and index name is 64, so we use `varchar(64)`. The documentation is [here](https://dev.mysql.com/doc/refman/5.7/en/identifier-length.html). |
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could you change the link to TiDB user doc?
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I did not find relevant information in TiDB user doc.
Co-authored-by: Zhang Jian <zjsariel@gmail.com>
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@rebelice,Thanks for your review. The bot only counts LGTMs from Reviewers and higher roles, but you're still welcome to leave your comments.You are not a reviewer or committer or co-leader or leader. |
| | TABLE_NAME | varchar | Name of the table or view on which the index is defined.| | ||
| | INDEX_NAME | varchar | Name of the index.| | ||
| | QUERY_COUNT | longlong | Number of the SQL using this index.| | ||
| | ROWS_SELECTED| longlong | Number of rows read from the index. We can check the selectivity of the index through `ROWS_READ` / `QUERY_COUNT`.| |
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I doubt that ROWS_READ / QUERY_COUNT means the selectivity of the index.
A QUERY_COUNT may lead many of ROWS_READ, ROWS_READ / QUERY_COUNT just means the average fetched rows count of each query.
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Makes sense, I will change its description.
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@rebelice,Thanks for your review. The bot only counts LGTMs from Reviewers and higher roles, but you're still welcome to leave your comments.You are not a reviewer or committer or co-leader or leader. |
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| ### SCHEMA_UNUSED_INDEXES | ||
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| Due to MySQL compatibility, add the system table `SCHEMA_UNUSED_INDEXES`. |
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MySQL's SCHEMA_UNUSED_INDEXES is under SYS database, should we also be compatible with that?
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Sounds reasonable. But I think create a SYS database is a big issue and may need to be discussed as a new, separate matter. What do you think?
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@rebelice,Thanks for your review. The bot only counts LGTMs from Reviewers and higher roles, but you're still welcome to leave your comments.You are not a reviewer or committer or co-leader or leader. |
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I'm going to close this PR since it hasn't been updated for a long time. feel free to reopen if you want to continue with it. thank you for your contribution. |
What problem does this PR solve?
Proposed a design doc for index usage information
Issue Number: related to #19209
Release note