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8px;width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;cursor:pointer;-webkit-tap-highlight-color:transparent;}.css-khel7y:hover{background-color:rgba(0, 0, 0, 0.04);}@media (hover: none){.css-khel7y:hover{background-color:transparent;}}.css-khel7y.Mui-disabled{opacity:0.38;background-color:transparent;}.css-khel7y.Mui-focused{background-color:rgba(0, 0, 0, 0.12);}.css-khel7y.Mui-selected{background-color:rgba(25, 118, 210, 0.08);}.css-khel7y.Mui-selected:hover{background-color:rgba(25, 118, 210, 0.12);}@media (hover: none){.css-khel7y.Mui-selected:hover{background-color:rgba(25, 118, 210, 0.08);}}.css-khel7y.Mui-selected.Mui-focused{background-color:rgba(25, 118, 210, 0.2);}.css-khel7y .MuiTreeItem-iconContainer{margin-right:4px;width:15px;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;-webkit-box-pack:center;-ms-flex-pack:center;-webkit-justify-content:center;justify-content:center;}.css-khel7y .MuiTreeItem-iconContainer svg{font-size:18px;}.css-khel7y .MuiTreeItem-label{width:100%;min-width:0;padding-left:4px;position:relative;font-size:1rem;line-height:1.5rem;font-family:"Helvetica Neue","sans-serif";font-weight:400;font-style:normal;color:#666666;}</style><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><style data-emotion="css znl8a3">.css-znl8a3{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:row;-ms-flex-direction:row;flex-direction:row;min-height:1.75rem;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;padding-left:0rem;padding-top:0.25rem;padding-bottom:0.25rem;}</style><div class="css-znl8a3"><style data-emotion="css tx8jsd">.css-tx8jsd{margin:0;font-size:1rem;line-height:1.5rem;font-family:"Helvetica Neue","sans-serif";font-weight:400;font-style:normal;color:#666666;}</style><a class="MuiTypography-root MuiTypography-body1 css-tx8jsd" target="_blank" href="https://docs.pingcap.com/zh" style="text-decoration:none;width:100%;color:inherit"><style data-emotion="css 8atqhb">.css-8atqhb{width:100%;}</style><div class="MuiBox-root css-8atqhb"><style data-emotion="css 1hwyipb">.css-1hwyipb{margin:0;font-size:1rem;line-height:1.5rem;font-family:"Helvetica Neue","sans-serif";font-weight:400;font-style:normal;color:#666666;color:inherit;font-size:0.875rem;line-height:1.25rem;}</style><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">文档中心</div></div></a></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-1" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">关于 TiDB</div></div><style data-emotion="css xjq79n">.css-xjq79n{-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none;width:1em;height:1em;display:inline-block;fill:currentColor;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;-webkit-transition:fill 200ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;transition:fill 200ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;font-size:1.5rem;fill:#999999;height:1rem;width:1rem;margin-left:auto;-webkit-transform:none;-moz-transform:none;-ms-transform:none;transform:none;}</style><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div><style data-emotion="css 1jozaee">.css-1jozaee{margin:0;padding:0;margin-left:17px;}</style></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-2" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">快速上手</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-3" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">应用开发</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-4" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">部署标准集群</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-5" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">数据迁移</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-6" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">数据集成</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-7" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">运维操作</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-8" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">监控与告警</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-9" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">故障诊断</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-10" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">性能调优</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-11" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">教程</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-12" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">TiDB 工具</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="true" id="left-nav-treeview-0-13" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content Mui-expanded" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-znl8a3"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">参考指南</div></div><style data-emotion="css 171pefp">.css-171pefp{-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none;width:1em;height:1em;display:inline-block;fill:currentColor;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;-webkit-transition:fill 200ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;transition:fill 200ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;font-size:1.5rem;fill:#999999;height:1rem;width:1rem;margin-left:auto;-webkit-transform:rotate(90deg);-moz-transform:rotate(90deg);-ms-transform:rotate(90deg);transform:rotate(90deg);}</style><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-171pefp" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div><style data-emotion="css 1xxsnna">.css-1xxsnna{height:auto;overflow:visible;-webkit-transition:height 300ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;transition:height 300ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;margin:0;padding:0;margin-left:17px;}</style><ul class="MuiCollapse-root MuiCollapse-vertical MuiTreeItem-group MuiCollapse-entered css-1xxsnna" style="min-height:0px" role="group"><div class="MuiCollapse-wrapper MuiCollapse-vertical css-hboir5"><div class="MuiCollapse-wrapperInner MuiCollapse-vertical css-8atqhb"><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-0" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><style data-emotion="css kb2j4b">.css-kb2j4b{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:row;-ms-flex-direction:row;flex-direction:row;min-height:1.75rem;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;padding-left:0.5rem;padding-top:0.25rem;padding-bottom:0.25rem;}</style><div class="css-kb2j4b"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">架构</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-1" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-kb2j4b"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">存储引擎 TiKV</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-2" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-kb2j4b"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">存储引擎 TiFlash</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" id="left-nav-treeview-0-13-3" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-kb2j4b"><a style="text-decoration:none;width:100%;color:inherit" href="/zh/tidb/dev/system-variables"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">系统变量</div></div></a></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-4" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-kb2j4b"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">配置文件参数</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-5" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-kb2j4b"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">CLI</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-6" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-kb2j4b"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">命令行参数</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-7" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div class="MuiTreeItem-iconContainer"/><div class="MuiTreeItem-label"><div class="css-kb2j4b"><div class="MuiBox-root css-8atqhb"><div class="MuiTypography-root MuiTypography-body1 css-1hwyipb">监控指标</div></div><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeMedium MuiTreeItem-ChevronRightIcon css-xjq79n" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="ChevronRightIcon"><path d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg></div></div></div></li><li class="MuiTreeItem-root css-1oy5rnm" role="treeitem" aria-expanded="false" id="left-nav-treeview-0-13-8" tabindex="-1" style="margin-top:0.1875rem;margin-bottom:0.1875rem"><div class="css-khel7y MuiTreeItem-content" style="width:inherit"><div 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class="MuiContainer-root MuiContainer-maxWidthXl doc-content css-1ekb41w"><div class="markdown-body MuiBox-root css-0"><h1 id="tidb-特有的函数" style="position:relative"><a href="#tidb-%E7%89%B9%E6%9C%89%E7%9A%84%E5%87%BD%E6%95%B0" aria-label="tidb 特有的函数 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TiDB 特有的函数</h1><p>本文档介绍 TiDB 特有的函数。</p><h2 id="tidb_bounded_staleness" style="position:relative"><a href="#tidb_bounded_staleness" aria-label="tidb_bounded_staleness permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_BOUNDED_STALENESS</h2><p><code>TIDB_BOUNDED_STALENESS</code> 是 TiDB 的内部函数，用于指定一个时间范围。用法为 <code>TIDB_BOUNDED_STALENESS(t1, t2)</code>，其中 t1 和 t2 为时间范围的两端，支持使用日期时间和时间函数。</p><p>使用该函数，TiDB 会在指定的时间范围内选择一个合适的时间戳，该时间戳能保证所访问的副本上不存在开始于这个时间戳之前且还没有提交的相关事务，即能保证所访问的可用副本上执行读取操作而且不会被阻塞。</p><h2 id="tidb_decode_key" style="position:relative"><a href="#tidb_decode_key" aria-label="tidb_decode_key permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_DECODE_KEY</h2><p><code>TIDB_DECODE_KEY</code> 函数用于将 TiDB 编码的键输入解码为包含 <code>_tidb_rowid</code> 和 <code>table_id</code> 的 JSON 结构。你可以在一些系统表和日志输出中找到 TiDB 的编码键。</p><h3 id="语法图" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE" aria-label="语法图 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>TableStmt</dt><dd><svg class="railroad-diagram" width="345" height="26" viewbox="0 0 345 26"><g transform="translate(.5 .5)"><g><path d="M2 9v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 13h10"/><g><path d="M32 13h0"/><path d="M313 13h0"/><g class="terminal"><path d="M32 13h0"/><path d="M202 13h0"/><rect x="32" y="2" width="170" height="22" rx="10" ry="10"/><text x="117" y="17">TIDB_DECODE_KEY(</text></g><path d="M202 13h10"/><path d="M212 13h10"/><g class="non-terminal"><path d="M222 13h0"/><path d="M266 13h0"/><rect x="222" y="2" width="44" height="22"/><text x="244" y="17">STR</text></g><path d="M266 13h10"/><path d="M276 13h10"/><g class="terminal"><path d="M286 13h0"/><path d="M313 13h0"/><rect x="286" y="2" width="27" height="22" rx="10" ry="10"/><text x="299.5" y="17">)</text></g></g><path d="M313 13h10"/><path d="M323 13h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">TableStmt ::= "TIDB_DECODE_KEY(" STR ")" </code></pre></div></div><h3 id="示例" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B" aria-label="示例 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><p>以下示例中，表 <code>t1</code> 有一个隐藏的 <code>rowid</code>，该 <code>rowid</code> 由 TiDB 生成。语句中使用了 <code>TIDB_DECODE_KEY</code> 函数。结果显示，隐藏的 <code>rowid</code> 被解码后并输出，这是典型的非聚簇主键结果。</p><pre><code class="language-sql">SELECT START_KEY, TIDB_DECODE_KEY(START_KEY) FROM information_schema.tikv_region_status WHERE table_name='t1' AND REGION_ID=2\G </code></pre><pre><code class="language-sql">*************************** 1. row *************************** START_KEY: 7480000000000000FF3B5F728000000000FF1DE3F10000000000FA TIDB_DECODE_KEY(START_KEY): {"_tidb_rowid":1958897,"table_id":"59"} 1 row in set (0.00 sec) </code></pre><p>以下示例中，表 <code>t2</code> 有一个复合聚簇主键。由 JSON 输出可知，输出结果的 <code>handle</code> 项中包含了主键部分两列的信息，即两列的名称和对应的值。</p><pre><code class="language-sql">show create table t2\G </code></pre><pre><code class="language-sql">*************************** 1. row *************************** Table: t2 Create Table: CREATE TABLE `t2` ( `id` binary(36) NOT NULL, `a` tinyint(3) unsigned NOT NULL, `v` varchar(512) DEFAULT NULL, PRIMARY KEY (`a`,`id`) /*T![clustered_index] CLUSTERED */ ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin 1 row in set (0.001 sec) </code></pre><pre><code class="language-sql">select * from information_schema.tikv_region_status where table_name='t2' limit 1\G </code></pre><pre><code class="language-sql">*************************** 1. row *************************** REGION_ID: 48 START_KEY: 7480000000000000FF3E5F720400000000FF0000000601633430FF3338646232FF2D64FF3531632D3131FF65FF622D386337352DFFFF3830653635303138FFFF61396265000000FF00FB000000000000F9 END_KEY: TABLE_ID: 62 DB_NAME: test TABLE_NAME: t2 IS_INDEX: 0 INDEX_ID: NULL INDEX_NAME: NULL EPOCH_CONF_VER: 1 EPOCH_VERSION: 38 WRITTEN_BYTES: 0 READ_BYTES: 0 APPROXIMATE_SIZE: 136 APPROXIMATE_KEYS: 479905 REPLICATIONSTATUS_STATE: NULL REPLICATIONSTATUS_STATEID: NULL 1 row in set (0.005 sec) </code></pre><pre><code class="language-sql">select tidb_decode_key('7480000000000000FF3E5F720400000000FF0000000601633430FF3338646232FF2D64FF3531632D3131FF65FF622D386337352DFFFF3830653635303138FFFF61396265000000FF00FB000000000000F9'); </code></pre><pre><code class="language-sql">+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | tidb_decode_key('7480000000000000FF3E5F720400000000FF0000000601633430FF3338646232FF2D64FF3531632D3131FF65FF622D386337352DFFFF3830653635303138FFFF61396265000000FF00FB000000000000F9') | +---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | {"handle":{"a":"6","id":"c4038db2-d51c-11eb-8c75-80e65018a9be"},"table_id":62} | +---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.001 sec) </code></pre><h3 id="mysql-兼容性" style="position:relative"><a href="#mysql-%E5%85%BC%E5%AE%B9%E6%80%A7" aria-label="mysql 兼容性 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>MySQL 兼容性</h3><p><code>TIDB_DECODE_KEY</code> 是 TiDB 特有的函数，和 MySQL 不兼容。</p><h2 id="tidb_decode_plan" style="position:relative"><a href="#tidb_decode_plan" aria-label="tidb_decode_plan permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_DECODE_PLAN</h2><p><code>TIDB_DECODE_PLAN</code> 函数用于解码 TiDB 执行计划。你可以在慢查询日志中找到 TiDB 执行计划。</p><h3 id="语法图-1" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE-1" aria-label="语法图 1 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>TableStmt</dt><dd><svg class="railroad-diagram" width="355" height="26" viewbox="0 0 355 26"><g transform="translate(.5 .5)"><g><path d="M2 9v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 13h10"/><g><path d="M32 13h0"/><path d="M323 13h0"/><g class="terminal"><path d="M32 13h0"/><path d="M212 13h0"/><rect x="32" y="2" width="180" height="22" rx="10" ry="10"/><text x="122" y="17">TIDB_DECODE_PLAN(</text></g><path d="M212 13h10"/><path d="M222 13h10"/><g class="non-terminal"><path d="M232 13h0"/><path d="M276 13h0"/><rect x="232" y="2" width="44" height="22"/><text x="254" y="17">STR</text></g><path d="M276 13h10"/><path d="M286 13h10"/><g class="terminal"><path d="M296 13h0"/><path d="M323 13h0"/><rect x="296" y="2" width="27" height="22" rx="10" ry="10"/><text x="309.5" y="17">)</text></g></g><path d="M323 13h10"/><path d="M333 13h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">TableStmt ::= "TIDB_DECODE_PLAN(" STR ")" </code></pre></div></div><h3 id="示例-1" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B-1" aria-label="示例 1 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><pre><code class="language-sql">SELECT tidb_decode_plan('8QIYMAkzMV83CQEH8E85LjA0CWRhdGE6U2VsZWN0aW9uXzYJOTYwCXRpbWU6NzEzLjHCtXMsIGxvb3BzOjIsIGNvcF90YXNrOiB7bnVtOiAxLCBtYXg6IDU2OC41wgErRHByb2Nfa2V5czogMCwgcnBjXxEpAQwFWBAgNTQ5LglZyGNvcHJfY2FjaGVfaGl0X3JhdGlvOiAwLjAwfQkzLjk5IEtCCU4vQQoxCTFfNgkxXzAJMwm2SGx0KHRlc3QudC5hLCAxMDAwMCkNuQRrdgmiAHsFbBQzMTMuOMIBmQnEDDk2MH0BUgEEGAoyCTQzXzUFVwX1oGFibGU6dCwga2VlcCBvcmRlcjpmYWxzZSwgc3RhdHM6cHNldWRvCTk2ISE2aAAIMTUzXmYA')\G </code></pre><pre><code class="language-sql">*************************** 1. row *************************** tidb_decode_plan('8QIYMAkzMV83CQEH8E85LjA0CWRhdGE6U2VsZWN0aW9uXzYJOTYwCXRpbWU6NzEzLjHCtXMsIGxvb3BzOjIsIGNvcF90YXNrOiB7bnVtOiAxLCBtYXg6IDU2OC41wgErRHByb2Nfa2V5czogMCwgcnBjXxEpAQwFWBAgNTQ5LglZyGNvcHJfY2FjaGVfaGl0X3JhdGlvOiAwLjAwfQkzLjk5IEtCCU4vQQoxCTFfNgkxXz: id task estRows operator info actRows execution info memory disk TableReader_7 root 319.04 data:Selection_6 960 time:713.1µs, loops:2, cop_task: {num: 1, max: 568.5µs, proc_keys: 0, rpc_num: 1, rpc_time: 549.1µs, copr_cache_hit_ratio: 0.00} 3.99 KB N/A └─Selection_6 cop[tikv] 319.04 lt(test.t.a, 10000) 960 tikv_task:{time:313.8µs, loops:960} N/A N/A └─TableFullScan_5 cop[tikv] 960 table:t, keep order:false, stats:pseudo 960 tikv_task:{time:153µs, loops:960} N/A N/A </code></pre><h3 id="mysql-兼容性-1" style="position:relative"><a href="#mysql-%E5%85%BC%E5%AE%B9%E6%80%A7-1" aria-label="mysql 兼容性 1 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>MySQL 兼容性</h3><p><code>TIDB_DECODE_PLAN</code> 是 TiDB 特有的函数，和 MySQL 不兼容。</p><h2 id="tidb_is_ddl_owner" style="position:relative"><a href="#tidb_is_ddl_owner" aria-label="tidb_is_ddl_owner permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_IS_DDL_OWNER</h2><p><code>TIDB_IS_DDL_OWNER</code> 函数用于检查你连接的 TiDB 实例是否是 DDL Owner。DDL Owner 代表集群中所有其他节点执行 DDL 语句的 TiDB 实例。</p><h3 id="语法图-2" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE-2" aria-label="语法图 2 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>TableStmt</dt><dd><svg class="railroad-diagram" width="269" height="26" viewbox="0 0 269 26"><g transform="translate(.5 .5)"><g><path d="M2 9v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 13h10"/><g class="terminal"><path d="M32 13h0"/><path d="M237 13h0"/><rect x="32" y="2" width="205" height="22" rx="10" ry="10"/><text x="134.5" y="17">TIDB_IS_DDL_OWNER())</text></g><path d="M237 13h10"/><path d="M247 13h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">TableStmt ::= "TIDB_IS_DDL_OWNER())" </code></pre></div></div><h3 id="示例-2" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B-2" aria-label="示例 2 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><pre><code class="language-sql">SELECT tidb_is_ddl_owner(); </code></pre><pre><code class="language-sql">+---------------------+ | tidb_is_ddl_owner() | +---------------------+ | 1 | +---------------------+ 1 row in set (0.00 sec) </code></pre><h3 id="mysql-兼容性-2" style="position:relative"><a href="#mysql-%E5%85%BC%E5%AE%B9%E6%80%A7-2" aria-label="mysql 兼容性 2 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>MySQL 兼容性</h3><p><code>TIDB_IS_DDL_OWNER</code> 是 TiDB 特有的函数，和 MySQL 不兼容。</p><h3 id="另请参阅" style="position:relative"><a href="#%E5%8F%A6%E8%AF%B7%E5%8F%82%E9%98%85" aria-label="另请参阅 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>另请参阅</h3><ul><li><a href="/zh/tidb/dev/sql-statement-admin-show-ddl">ADMIN SHOW DDL</a></li><li><a href="/zh/tidb/dev/sql-statement-admin-cancel-ddl">ADMIN CANCEL DDL</a></li></ul><h2 id="tidb_parse_tso" style="position:relative"><a href="#tidb_parse_tso" aria-label="tidb_parse_tso permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_PARSE_TSO</h2><p><code>TIDB_PARSE_TSO</code> 函数用于从 TiDB TSO 时间戳中提取物理时间戳。</p><p>TSO 指 Time Stamp Oracle，是 PD (Placement Driver) 为每个事务提供的单调递增的时间戳。</p><p>TSO 是一串数字，包含以下两部分：</p><ul><li>一个物理时间戳</li><li>一个逻辑计数器</li></ul><h3 id="语法图-3" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE-3" aria-label="语法图 3 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>TableStmt</dt><dd><svg class="railroad-diagram" width="337" height="26" viewbox="0 0 337 26"><g transform="translate(.5 .5)"><g><path d="M2 9v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 13h10"/><g><path d="M32 13h0"/><path d="M305 13h0"/><g class="terminal"><path d="M32 13h0"/><path d="M190 13h0"/><rect x="32" y="2" width="158" height="22" rx="10" ry="10"/><text x="111" y="17">TIDB_PARSE_TSO(</text></g><path d="M190 13h10"/><path d="M200 13h10"/><g class="non-terminal"><path d="M210 13h0"/><path d="M258 13h0"/><rect x="210" y="2" width="48" height="22"/><text x="234" y="17">NUM</text></g><path d="M258 13h10"/><path d="M268 13h10"/><g class="terminal"><path d="M278 13h0"/><path d="M305 13h0"/><rect x="278" y="2" width="27" height="22" rx="10" ry="10"/><text x="291.5" y="17">)</text></g></g><path d="M305 13h10"/><path d="M315 13h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">TableStmt ::= "TIDB_PARSE_TSO(" NUM ")" </code></pre></div></div><h3 id="示例-3" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B-3" aria-label="示例 3 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><pre><code class="language-sql">BEGIN; SELECT TIDB_PARSE_TSO(@@tidb_current_ts); ROLLBACK; </code></pre><pre><code class="language-sql">+-----------------------------------+ | TIDB_PARSE_TSO(@@tidb_current_ts) | +-----------------------------------+ | 2021-05-26 11:33:37.776000 | +-----------------------------------+ 1 row in set (0.0012 sec) </code></pre><p>以上示例使用 <code>TIDB_PARSE_TSO</code> 函数从 <code>tidb_current_ts</code> 会话变量提供的可用时间戳编号中提取物理时间戳。因为每个事务都会分配到时间戳，所以此函数在事务中运行。</p><h3 id="mysql-兼容性-3" style="position:relative"><a href="#mysql-%E5%85%BC%E5%AE%B9%E6%80%A7-3" aria-label="mysql 兼容性 3 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>MySQL 兼容性</h3><p><code>TIDB_PARSE_TSO</code> 是 TiDB 特有的函数，和 MySQL 不兼容。</p><h3 id="另请参阅-1" style="position:relative"><a href="#%E5%8F%A6%E8%AF%B7%E5%8F%82%E9%98%85-1" aria-label="另请参阅 1 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>另请参阅</h3><ul><li><a href="/zh/tidb/dev/system-variables#tidb_current_ts"><code>tidb_current_ts</code></a></li></ul><h2 id="tidb_version" style="position:relative"><a href="#tidb_version" aria-label="tidb_version permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_VERSION</h2><p><code>TIDB_VERSION</code> 函数用于获取当前连接的 TiDB 服务器版本和构建详细信息。向 GitHub 上提交 issue 时，你可使用此函数获取相关信息。</p><h3 id="语法图-4" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE-4" aria-label="语法图 4 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>TableStmt</dt><dd><svg class="railroad-diagram" width="209" height="26" viewbox="0 0 209 26"><g transform="translate(.5 .5)"><g><path d="M2 9v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 13h10"/><g class="terminal"><path d="M32 13h0"/><path d="M177 13h0"/><rect x="32" y="2" width="145" height="22" rx="10" ry="10"/><text x="104.5" y="17">TIDB_VERSION()</text></g><path d="M177 13h10"/><path d="M187 13h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">TableStmt ::= "TIDB_VERSION()" </code></pre></div></div><h3 id="示例-4" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B-4" aria-label="示例 4 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><pre><code class="language-sql">SELECT TIDB_VERSION()\G </code></pre><pre><code class="language-sql">*************************** 1. row *************************** TIDB_VERSION(): Release Version: v5.1.0-alpha-13-gd5e0ed0aa-dirty Edition: Community Git Commit Hash: d5e0ed0aaed72d2f2dfe24e9deec31cb6cb5fdf0 Git Branch: master UTC Build Time: 2021-05-24 14:39:20 GoVersion: go1.13 Race Enabled: false TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306 Check Table Before Drop: false 1 row in set (0.00 sec) </code></pre><h3 id="mysql-兼容性-4" style="position:relative"><a href="#mysql-%E5%85%BC%E5%AE%B9%E6%80%A7-4" aria-label="mysql 兼容性 4 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>MySQL 兼容性</h3><p><code>TIDB_VERSION</code> 是 TiDB 特有的函数，和 MySQL 不兼容。如果要求兼容 MySQL，可以使用 <code>VERSION</code> 获取版本信息，但结果不包含详细的构建信息。</p><h2 id="tidb_decode_sql_digests" style="position:relative"><a href="#tidb_decode_sql_digests" aria-label="tidb_decode_sql_digests permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_DECODE_SQL_DIGESTS</h2><p><code>TIDB_DECODE_SQL_DIGESTS</code> 函数用于在集群中查询一组 SQL Digest 所对应的 SQL 语句的归一化形式（即去除格式和参数后的形式）。函数接受 1 个或 2 个参数：</p><ul><li><code>digests</code>：字符串类型，该参数应符合 JSON 字符串数组的格式，数组中的每个字符串应为一个 SQL Digest。</li><li><code>stmtTruncateLength</code>：可选参数，整数类型，用来限制返回结果中每条 SQL 语句的长度，超过指定的长度会被截断。0 表示不限制长度。</li></ul><p>返回一个字符串，符合 JSON 字符串数组的格式，数组中的第 <em>i</em> 项为参数 <code>digests</code> 中的第 <em>i</em> 个元素所对应的语句。如果参数 <code>digests</code> 中的某一项不是一个有效的 SQL Digest 或系统无法查询到其对应的 SQL 语句，则返回结果中对应项为 <code>null</code>。如果指定了截断长度（<code>stmtTruncateLength &gt; 0</code>），则返回结果中每条超过该长度的语句，保留前 <code>stmtTruncateLength</code> 个字符，并在尾部增加 <code>"..."</code> 后缀表示发生了截断。如果参数 <code>digests</code> 为 <code>NULL</code>，则函数的返回值为 <code>NULL</code>。</p><style data-emotion="css 1weqspv">.css-1weqspv{padding-top:0.5rem;padding-bottom:0.5rem;}.css-1weqspv .MuiAlert-message p{margin-bottom:0px;margin-top:0px;}</style><div class="MuiBox-root css-1weqspv"><style data-emotion="css 17zlexa">.css-17zlexa{font-size:0.875rem;line-height:1.25rem;font-family:"Helvetica Neue","sans-serif";font-weight:400;font-style:normal;color:rgb(1, 67, 97);background-color:rgb(229, 246, 253);display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;padding:6px 16px;}.css-17zlexa .MuiAlert-icon{color:#03a9f4;}</style><style data-emotion="css 152gid5">.css-152gid5{background-color:#fff;color:rgba(0, 0, 0, 0.87);-webkit-transition:box-shadow 300ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;transition:box-shadow 300ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;border-radius:4px;box-shadow:none;font-size:0.875rem;line-height:1.25rem;font-family:"Helvetica Neue","sans-serif";font-weight:400;font-style:normal;color:rgb(1, 67, 97);background-color:rgb(229, 246, 253);display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;padding:6px 16px;}.css-152gid5 .MuiAlert-icon{color:#03a9f4;}</style><div class="MuiPaper-root MuiPaper-elevation MuiPaper-rounded MuiPaper-elevation0 MuiAlert-root MuiAlert-standardInfo MuiAlert-standard css-152gid5" role="alert"><style data-emotion="css 1l54tgj">.css-1l54tgj{margin-right:12px;padding:7px 0;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;font-size:22px;opacity:0.9;}</style><div class="MuiAlert-icon css-1l54tgj"><style data-emotion="css 1cw4hi4">.css-1cw4hi4{-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;user-select:none;width:1em;height:1em;display:inline-block;fill:currentColor;-webkit-flex-shrink:0;-ms-flex-negative:0;flex-shrink:0;-webkit-transition:fill 200ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;transition:fill 200ms cubic-bezier(0.4, 0, 0.2, 1) 0ms;font-size:inherit;}</style><svg class="MuiSvgIcon-root MuiSvgIcon-fontSizeInherit css-1cw4hi4" focusable="false" aria-hidden="true" viewbox="0 0 24 24" data-testid="InfoOutlinedIcon"><path d="M11,9H13V7H11M12,20C7.59,20 4,16.41 4,12C4,7.59 7.59,4 12,4C16.41,4 20,7.59 20, 12C20,16.41 16.41,20 12,20M12,2A10,10 0 0,0 2,12A10,10 0 0,0 12,22A10,10 0 0,0 22,12A10, 10 0 0,0 12,2M11,17H13V11H11V17Z"/></svg></div><style data-emotion="css 1xsto0d">.css-1xsto0d{padding:8px 0;min-width:0;overflow:auto;}</style><div class="MuiAlert-message css-1xsto0d"><style data-emotion="css 1h2y6o4">.css-1h2y6o4{font-weight:500;margin-top:-2px;}</style><style data-emotion="css 17ioyuk">.css-17ioyuk{margin:0;font-size:1rem;line-height:1.5rem;font-family:"Helvetica Neue","sans-serif";font-weight:400;font-style:normal;color:#666666;margin-bottom:0.35em;font-weight:500;margin-top:-2px;}</style><div class="MuiTypography-root MuiTypography-body1 MuiTypography-gutterBottom MuiAlertTitle-root css-17ioyuk">注意</div><ul><li>仅持有 <a href="https://dev.mysql.com/doc/refman/8.0/en/privileges-provided.html#priv_process" target="_blank" referrerpolicy="no-referrer-when-downgrade">PROCESS</a> 权限的用户可以使用该函数。</li><li><code>TIDB_DECODE_SQL_DIGESTS</code> 执行时，TiDB 内部从 Statement Summary 一系列表中查询每个 SQL Digest 所对应的语句，因而并不能保证对任意 SQL Digest 都总是能查询到对应的语句，只有在集群中执行过的语句才有可能被查询到，且是否能查询到受 Statement Summary 表相关配置的影响。有关 Statement Summary 表的详细说明，参见 <a href="/zh/tidb/dev/statement-summary-tables">Statement Summary Tables</a>。</li><li>该函数开销较大，在行数很多的查询中（比如在规模较大、比较繁忙的集群上查询 <code>information_schema.cluster_tidb_trx</code> 全表时）直接使用该函数可能导致查询运行时间较长。请谨慎使用。<ul><li>该函数开销大的原因是，其每次被调用时，都会在内部发起对 <code>STATEMENTS_SUMMARY</code>、<code>STATEMENTS_SUMMARY_HISTORY</code>、<code>CLUSTER_STATEMENTS_SUMMARY</code> 和 <code>CLUSTER_STATEMENTS_SUMMARY_HISTORY</code> 这几张表的查询，且其中涉及 <code>UNION</code> 操作。且该函数目前不支持向量化，即对于多行数据调用该函数时，对每行都会独立进行一次上述的查询。</li></ul></li></ul></div></div></div><h3 id="语法图-5" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE-5" aria-label="语法图 5 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>DecodeSQLDigestsExpr</dt><dd><svg class="railroad-diagram" width="708" height="35" viewbox="0 0 708 35"><g transform="translate(.5 .5)"><g><path d="M2 18v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 22h10"/><g><path d="M32 22h0"/><path d="M676 22h0"/><g class="terminal"><path d="M32 22h0"/><path d="M272 22h0"/><rect x="32" y="11" width="240" height="22" rx="10" ry="10"/><text x="152" y="26">TIDB_DECODE_SQL_DIGESTS</text></g><path d="M272 22h10"/><path d="M282 22h10"/><g class="terminal"><path d="M292 22h0"/><path d="M319 22h0"/><rect x="292" y="11" width="27" height="22" rx="10" ry="10"/><text x="305.5" y="26">(</text></g><path d="M319 22h10"/><path d="M329 22h10"/><g class="non-terminal"><path d="M339 22h0"/><path d="M402 22h0"/><rect x="339" y="11" width="63" height="22"/><text x="370.5" y="26">digests</text></g><path d="M402 22h10"/><g><path d="M412 22h0"/><path d="M639 22h0"/><path d="M412 22a10 10 0 0 0 10 -10v0a10 10 0 0 1 10 -10"/><g><path d="M432 2h187"/></g><path d="M619 2a10 10 0 0 1 10 10v0a10 10 0 0 0 10 10"/><path d="M412 22h20"/><g><path d="M432 22h0"/><path d="M619 22h0"/><g class="terminal"><path d="M432 22h0"/><path d="M457 22h0"/><rect x="432" y="11" width="25" height="22" rx="10" ry="10"/><text x="444.5" y="26">,</text></g><path d="M457 22h10"/><path d="M467 22h10"/><g class="non-terminal"><path d="M477 22h0"/><path d="M619 22h0"/><rect x="477" y="11" width="142" height="22"/><text x="548" y="26">stmtTruncateLength</text></g></g><path d="M619 22h20"/></g><path d="M639 22h10"/><g class="terminal"><path d="M649 22h0"/><path d="M676 22h0"/><rect x="649" y="11" width="27" height="22" rx="10" ry="10"/><text x="662.5" y="26">)</text></g></g><path d="M676 22h10"/><path d="M686 22h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">DecodeSQLDigestsExpr ::= "TIDB_DECODE_SQL_DIGESTS" "(" digests ( "," stmtTruncateLength )? ")" </code></pre></div></div><h3 id="示例-5" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B-5" aria-label="示例 5 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><pre><code class="language-sql">set @digests = '["e6f07d43b5c21db0fbb9a31feac2dc599787763393dd5acbfad80e247eb02ad5","38b03afa5debbdf0326a014dbe5012a62c51957f1982b3093e748460f8b00821","e5796985ccafe2f71126ed6c0ac939ffa015a8c0744a24b7aee6d587103fd2f7"]'; select tidb_decode_sql_digests(@digests); </code></pre><pre><code class="language-sql">+------------------------------------+ | tidb_decode_sql_digests(@digests) | +------------------------------------+ | ["begin",null,"select * from `t`"] | +------------------------------------+ 1 row in set (0.00 sec) </code></pre><p>上面的例子中，参数是一个包含 3 个 SQL Digest 的 JSON 数组，其对应的 SQL 语句分别为查询结果中给出的三项。但是其中第二条 SQL Digest 所对应的 SQL 语句未能从集群中找到，因而结果中的第二项为 <code>null</code>。</p><pre><code class="language-sql">select tidb_decode_sql_digests(@digests, 10); </code></pre><pre><code class="language-sql">+---------------------------------------+ | tidb_decode_sql_digests(@digests, 10) | +---------------------------------------+ | ["begin",null,"select * f..."] | +---------------------------------------+ 1 row in set (0.01 sec) </code></pre><p>上述调用指定了第二个参数（即截断长度）为 10，而查询结果中的第三条语句的长度大于 10，因而仅保留了前 10 个字符，并在尾部添加了 <code>"..."</code> 表示发生了截断。</p><h3 id="mysql-兼容性-5" style="position:relative"><a href="#mysql-%E5%85%BC%E5%AE%B9%E6%80%A7-5" aria-label="mysql 兼容性 5 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>MySQL 兼容性</h3><p><code>TIDB_DECODE_SQL_DIGESTS</code> 是 TiDB 特有的函数，和 MySQL 不兼容。</p><h3 id="另请参阅-2" style="position:relative"><a href="#%E5%8F%A6%E8%AF%B7%E5%8F%82%E9%98%85-2" aria-label="另请参阅 2 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>另请参阅</h3><ul><li><a href="/zh/tidb/dev/statement-summary-tables"><code>Statement Summary Tables</code></a></li><li><a href="/zh/tidb/dev/information-schema-tidb-trx"><code>INFORMATION_SCHEMA.TIDB_TRX</code></a></li></ul><h2 id="tidb_shard" style="position:relative"><a href="#tidb_shard" aria-label="tidb_shard permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_SHARD</h2><p><code>TIDB_SHARD</code> 函数用于创建一个 SHARD INDEX 来打散热点索引。SHARD INDEX 是一种以 <code>TIDB_SHARD</code> 函数为前缀的表达式索引。</p><h3 id="shard-index" style="position:relative"><a href="#shard-index" aria-label="shard index permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>SHARD INDEX</h3><ul><li><p>创建方式：</p><p> 使用 <code>uk((tidb_shard(a)), a))</code> 为字段 <code>a</code> 创建一个 SHARD INDEX。当二级唯一索引 <code>uk((tidb_shard(a)), a))</code> 的索引字段 <code>a</code> 上存在因单调递增或递减而产生的热点时，索引的前缀 <code>tidb_shard(a)</code> 会打散热点，从而提升集群可扩展性。</p></li><li><p>适用场景：</p><ul><li>二级唯一索引上 key 值存在单调递增或递减导致的写入热点，且该索引包含的列是整型。</li><li>业务中 SQL 语句根据该二级索引的全部字段做等值查询，查询可以是单独的 <code>SELECT</code>，也可以是 <code>UPDATE</code>，<code>DELETE</code> 等产生的内部查询，等值查询包括 <code>a = 1</code> 或 <code>a IN (1, 2, ......)</code> 两种方式。</li></ul></li><li><p>使用限制：</p><ul><li>非等值查询无法使用索引。</li><li>查询条件中 <code>AND</code> 和 <code>OR</code> 混合且最外层是 <code>AND</code> 算子时无法使用 SHARD INDEX。</li><li><code>GROUP BY</code> 无法使用 SHARD INDEX。</li><li><code>ORDER BY</code> 无法使用 SHARD INDEX。</li><li><code>ON</code> 子句无法使用 SHARD INDEX。</li><li><code>WHERE</code> 子查询无法使用 SHARD INDEX。</li><li>SHARD INDEX 只能打散整型字段的唯一索引。</li><li>SHARD INDEX 联合索引可能失效。</li><li>SHARD INDEX 无法走 FastPlan 流程，影响优化器性能。</li><li>SHARD INDEX 无法使用执行计划缓存。</li></ul></li></ul><h3 id="语法图-6" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE-6" aria-label="语法图 6 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>TIDBShardExpr</dt><dd><svg class="railroad-diagram" width="342" height="26" viewbox="0 0 342 26"><g transform="translate(.5 .5)"><g><path d="M2 9v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 13h10"/><g><path d="M32 13h0"/><path d="M310 13h0"/><g class="terminal"><path d="M32 13h0"/><path d="M149 13h0"/><rect x="32" y="2" width="117" height="22" rx="10" ry="10"/><text x="90.5" y="17">TIDB_SHARD</text></g><path d="M149 13h10"/><path d="M159 13h10"/><g class="terminal"><path d="M169 13h0"/><path d="M196 13h0"/><rect x="169" y="2" width="27" height="22" rx="10" ry="10"/><text x="182.5" y="17">(</text></g><path d="M196 13h10"/><path d="M206 13h10"/><g class="non-terminal"><path d="M216 13h0"/><path d="M263 13h0"/><rect x="216" y="2" width="47" height="22"/><text x="239.5" y="17">expr</text></g><path d="M263 13h10"/><path d="M273 13h10"/><g class="terminal"><path d="M283 13h0"/><path d="M310 13h0"/><rect x="283" y="2" width="27" height="22" rx="10" ry="10"/><text x="296.5" y="17">)</text></g></g><path d="M310 13h10"/><path d="M320 13h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">TIDBShardExpr ::= "TIDB_SHARD" "(" expr ")" </code></pre></div></div><h3 id="示例-6" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B-6" aria-label="示例 6 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><ul><li><p>使用 <code>TIDB_SHARD</code> 函数计算 SHARD 值</p><p> 以下示例说明如何使用 <code>TIDB_SHARD</code> 函数计算 <code>12373743746</code> 的 SHARD 值。</p><pre><code class="language-sql">SELECT TIDB_SHARD(12373743746); </code></pre></li><li><p>计算得出 SHARD 值为：</p><pre><code class="language-sql">+-------------------------+ | TIDB_SHARD(12373743746) | +-------------------------+ | 184 | +-------------------------+ 1 row in set (0.00 sec) </code></pre></li><li><p>使用 <code>TIDB_SHARD</code> 函数创建 SHARD INDEX</p><pre><code class="language-sql">CREATE TABLE test(id INT PRIMARY KEY CLUSTERED, a INT, b INT, UNIQUE KEY uk((tidb_shard(a)), a)); </code></pre></li></ul><h3 id="mysql-兼容性-6" style="position:relative"><a href="#mysql-%E5%85%BC%E5%AE%B9%E6%80%A7-6" aria-label="mysql 兼容性 6 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>MySQL 兼容性</h3><p><code>TIDB_SHARD</code> 是 TiDB 特有的函数，和 MySQL 不兼容。</p><h2 id="tidb_row_checksum" style="position:relative"><a href="#tidb_row_checksum" aria-label="tidb_row_checksum permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>TIDB_ROW_CHECKSUM</h2><p><code>TIDB_ROW_CHECKSUM</code> 函数用于查询行数据的 Checksum 值。该函数只能用于 FastPlan 流程的 <code>SELECT</code> 语句，即你可通过形如 <code>SELECT TIDB_ROW_CHECKSUM() FROM t WHERE id = ?</code> 或 <code>SELECT TIDB_ROW_CHECKSUM() FROM t WHERE id IN (?, ?, ...)</code> 的语句进行查询。</p><h3 id="语法图-7" style="position:relative"><a href="#%E8%AF%AD%E6%B3%95%E5%9B%BE-7" aria-label="语法图 7 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>语法图</h3><div class="syntax-diagram-module--root--vJoVV"><div class="syntax-diagram-module--toolbar--0ABqv buttons are-small are-light has-addons is-right"><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0z"/><path d="M22 11V3h-7v3H9V3H2v8h7V8h2v10h4v3h7v-8h-7v3h-2V8h2v3h7zM7 9H4V5h3v4zm10 6h3v4h-3v-4zm0-10h3v4h-3V5z"/></svg></span><span>语法图</span></button><button class="button is-light"><span class="icon"><svg stroke="currentColor" fill="currentColor" stroke-width="0" viewbox="0 0 24 24" height="1em" width="1em" xmlns="http://www.w3.org/2000/svg"><path fill="none" d="M0 0h24v24H0V0z"/><path d="M9.4 16.6L4.8 12l4.6-4.6L8 6l-6 6 6 6 1.4-1.4zm5.2 0l4.6-4.6-4.6-4.6L16 6l6 6-6 6-1.4-1.4z"/></svg></span><span>代码</span></button></div><div class="syntax-diagram-module--container--eSGQz"><dl><dt>TableStmt</dt><dd><svg class="railroad-diagram" width="269" height="26" viewbox="0 0 269 26"><g transform="translate(.5 .5)"><g><path d="M2 9v8l8-4Zm8 0v8l8-4Zm8 4h4" class="start-end"/></g><path d="M22 13h10"/><g class="terminal"><path d="M32 13h0"/><path d="M237 13h0"/><rect x="32" y="2" width="205" height="22" rx="10" ry="10"/><text x="134.5" y="17">TIDB_ROW_CHECKSUM()</text></g><path d="M237 13h10"/><path d="M247 13h4m0-4v8l16-8v8Z" class="start-end"/></g></svg></dd></dl></div><div hidden=""><pre><code class="language-ebnf">TableStmt ::= "TIDB_ROW_CHECKSUM()" </code></pre></div></div><h3 id="示例-7" style="position:relative"><a href="#%E7%A4%BA%E4%BE%8B-7" aria-label="示例 7 permalink" class="anchor before"><svg aria-hidden="true" focusable="false" height="16" version="1.1" viewbox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"/></svg></a>示例</h3><p>在 TiDB 中开启行数据 Checksum 功能 <a href="/zh/tidb/dev/system-variables#tidb_enable_row_level_checksum-从-v710-版本开始引入"><code>tidb_enable_row_level_checksum</code></a>：</p><pre><code class="language-sql">SET GLOBAL tidb_enable_row_level_checksum = ON; </code></pre><p>创建表 <code>t</code> 并插入数据：</p><pre><code class="language-sql">USE test; CREATE TABLE t (id INT PRIMARY KEY, k INT, c int); INSERT INTO TABLE t values (1, 10, a); </code></pre><p>查询表 <code>t</code> 中 <code>id = 1</code> 的行数据的 Checksum 值：</p><pre><code class="language-sql">SELECT *, TIDB_ROW_CHECKSUM() FROM t WHERE id = 1; </code></pre><pre><code class="language-sql">+----+------+------+---------------------+