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padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label="页面路径"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a aria-label="主页面" class="breadcrumbs__link" href="/zh/"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_OVgt"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item"><a class="breadcrumbs__link" itemprop="item" href="/zh/docs/v0.19/DeveloperManuals"><span itemprop="name">Developer Manuals</span></a><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">DB Migration</span><meta itemprop="position" content="2"></li></ul></nav><span class="theme-doc-version-badge badge badge--secondary">版本：v0.19</span><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">本页总览</button></div><div class="theme-doc-markdown markdown"><header><h1>DB Migration</h1></header><h2 class="anchor anchorWithStickyNavbar_LWe7" id="summary">Summary<a class="hash-link" href="#summary" title="标题的直接链接"></a></h2><p>Starting in v0.10.0, DevLake provides a lightweight migration tool for executing migration scripts. |
| The method <code>Up</code> contains the steps of migration.</p><div class="language-go codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-go codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token keyword" style="color:#00009f">type</span><span class="token plain"> MigrationScript </span><span class="token keyword" style="color:#00009f">interface</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// this function will contain the business logic of the migration (e.g. DDL logic)</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">Up</span><span class="token punctuation" style="color:#393A34">(</span><span class="token plain">basicRes BasicRes</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> errors</span><span class="token punctuation" style="color:#393A34">.</span><span class="token plain">Error</span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// the version number of the migration. typically in date format (YYYYMMDDHHMMSS), e.g. 20220728000001. Migrations are executed sequentially based on this number.</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">Version</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token builtin">uint64</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token comment" style="color:#999988;font-style:italic">// The name of this migration</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"> </span><span class="token function" style="color:#d73a49">Name</span><span class="token punctuation" style="color:#393A34">(</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token builtin">string</span><span class="token plain"></span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="复制代码到剪贴板" title="复制" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><h2 class="anchor anchorWithStickyNavbar_LWe7" id="the-migration-model">The Migration Model<a class="hash-link" href="#the-migration-model" title="标题的直接链接"></a></h2><p>For each migration, we define a "snapshot" datamodel of the model that we wish to perform the migration on. |
| for the framework-only migrations defined under the <code>models</code> package.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="how-it-works">How It Works<a class="hash-link" href="#how-it-works" title="标题的直接链接"></a></h2><ol><li>Check <code>migration_history</code> table, calculate all the migration scripts need to be executed.</li><li>Sort scripts by <code>Version</code> and <code>Name</code> in ascending order. Please do NOT change these two values for the script after release for any reasons; otherwise, users may fail to upgrade due to the duplicated execution.</li><li>Execute the scripts.</li><li>Save the results in the <code>migration_history</code> table.</li></ol><h2 class="anchor anchorWithStickyNavbar_LWe7" id="best-practices">Best Practices<a class="hash-link" href="#best-practices" title="标题的直接链接"></a></h2><p>When you write a new migration script, please pay attention to the fault tolerance and the side effect. It would be better if the failed script could be safely retried, in case if something goes wrong during the migration. For this purpose, the migration scripts should be well-designed. For example, if you have created a temporary table in the Up method, it should be dropped before exiting, regardless of success or failure.</p><p>Suppose we want to change the type of the Primary Key <code>name</code> of table <code>users</code> from <code>int</code> to <code>varchar(255)</code></p><ol><li>Rename <code>users</code> to <code>users_20221018</code> (stop if error, otherwise define a <code>defer</code> to rename back on error)</li><li>Create new <code>users</code> (stop if error, otherwise define a <code>defer</code> to drop the table on error)</li><li>Convert data from <code>users_20221018</code> to <code>users</code> (stop if error)</li><li>Drop table <code>users_20221018</code></li></ol><p>With these steps, the <code>defer</code> functions would be executed in reverse order if any error occurred during the migration process so the database would roll back to the original state in most cases.</p><p>However, you don't neccessary deal with all the mess. We had summarized some of the most useful code examples for you to follow:</p><ul><li>[Create new tables]<a href="https://github.com/apache/incubator-devlake/blob/main/backend/core/models/migrationscripts/20220406_add_frame_tables.go" target="_blank" rel="noopener noreferrer">https://github.com/apache/incubator-devlake/blob/main/backend/core/models/migrationscripts/20220406_add_frame_tables.go</a>) |
