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This is a template for TiDB's change proposal process, documented [here](./README.md).
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# Proposal: <!-- Title -->

- Author(s):     <!-- Author Name, Co-Author Name, with the link(s) of the GitHub profile page -->
- Last updated:  <!-- Date -->
- Discussion at: <!-- https://github.com/pingcap/tidb/issues/XXX -->

## Abstract

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A short summary of the proposal:
- What is the issue that the proposal aims to solve?
- What needs to be done in this proposal?
- What is the impact of this proposal?
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## Background

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An introduction of the necessary background and the problem being solved by the proposed change:
- The drawback of the current feature and the corresponding use case
- The expected outcome of this proposal.
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## Proposal

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A precise statement of the proposed change:
- The new named concepts and a set of metrics to be collected in this proposal (if applicable)
- The overview of the design.
- How it works?
- What needs to be changed to implement this design?
- What may be positively influenced by the proposed change?
- What may be negatively impacted by the proposed change?
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## Rationale

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A discussion of alternate approaches and the trade-offs, advantages, and disadvantages of the specified approach:
- How other systems solve the same issue?
- What other designs have been considered and what are their disadvantages?
- What is the advantage of this design compared with other designs?
- What is the disadvantage of this design?
- What is the impact of not doing this?
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## Compatibility and Mirgration Plan

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A discussion of the change with regard to the compatibility issues:
- Does this proposal make TiDB not compatible with the old versions?
- If the existing behavior will be changed, how will we phase out the older behavior?
- Does this proposal make TiDB more compatible with MySQL?
- What is the impact(if any) on the data migration:
    + from MySQL to TiDB
    + from TiDB to MySQL
    + from old TiDB cluster to new TiDB cluster
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## Implementation

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A detailed description for each step in the implementation:
- Does any former steps block this step?
- Who will do it?
- When to do it?
- How long it takes to accomplish it?
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## Testing Plan

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A brief description on how the implementation will be tested. Both integration test and unit test should consider the following things:
- How to ensure that the implementation works as expected?
- How will we know nothing broke?
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## Open issues (if applicable)

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A discussion of issues relating to this proposal for which the author does not know the solution. This section may be omitted if there are none.
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