<!DOCTYPE HTML> <html lang="en" class="sidebar-visible no-js light"> <head> <!-- Book generated using mdBook --> <meta charset="UTF-8"> <title>Database Schemas - Synapse</title> <!-- Custom HTML head --> <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> <meta name="description" content=""> <meta name="viewport" content="width=device-width, initial-scale=1"> <meta name="theme-color" content="#ffffff" /> <link rel="icon" href="../favicon.svg"> <link rel="shortcut icon" href="../favicon.png"> <link rel="stylesheet" href="../css/variables.css"> <link rel="stylesheet" href="../css/general.css"> <link rel="stylesheet" href="../css/chrome.css"> <link rel="stylesheet" href="../css/print.css" media="print"> <!-- Fonts --> <link rel="stylesheet" href="../FontAwesome/css/font-awesome.css"> <link rel="stylesheet" href="../fonts/fonts.css"> <!-- Highlight.js Stylesheets --> <link rel="stylesheet" href="../highlight.css"> <link rel="stylesheet" href="../tomorrow-night.css"> <link rel="stylesheet" href="../ayu-highlight.css"> <!-- Custom theme stylesheets --> <link rel="stylesheet" href="../docs/website_files/table-of-contents.css"> <link rel="stylesheet" href="../docs/website_files/remove-nav-buttons.css"> <link rel="stylesheet" href="../docs/website_files/indent-section-headers.css"> </head> <body> <!-- Provide site root to javascript --> <script type="text/javascript"> var path_to_root = "../"; var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? 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Proxy</a></li><li class="chapter-item expanded "><a href="../setup/forward_proxy.html">Configuring a Forward/Outbound Proxy</a></li><li class="chapter-item expanded "><a href="../turn-howto.html">Configuring a Turn Server</a></li><li class="chapter-item expanded "><a href="../delegate.html">Delegation</a></li><li class="chapter-item expanded affix "><li class="part-title">Upgrading</li><li class="chapter-item expanded "><a href="../upgrade.html">Upgrading between Synapse Versions</a></li><li class="chapter-item expanded "><a href="../MSC1711_certificates_FAQ.html">Upgrading from pre-Synapse 1.0</a></li><li class="chapter-item expanded affix "><li class="part-title">Usage</li><li class="chapter-item expanded "><a href="../federate.html">Federation</a></li><li class="chapter-item expanded "><a href="../usage/configuration/index.html">Configuration</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../usage/configuration/homeserver_sample_config.html">Homeserver 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"><div>Scripts</div></li></ol></li><li class="chapter-item expanded "><li class="part-title">Development</li><li class="chapter-item expanded "><a href="../development/contributing_guide.html">Contributing Guide</a></li><li class="chapter-item expanded "><a href="../code_style.html">Code Style</a></li><li class="chapter-item expanded "><a href="../development/git.html">Git Usage</a></li><li class="chapter-item expanded "><div>Testing</div></li><li class="chapter-item expanded "><a href="../opentracing.html">OpenTracing</a></li><li class="chapter-item expanded "><a href="../development/database_schema.html" class="active">Database Schemas</a></li><li class="chapter-item expanded "><a href="../development/experimental_features.html">Experimental features</a></li><li class="chapter-item expanded "><div>Synapse Architecture</div></li><li><ol class="section"><li class="chapter-item expanded "><a href="../log_contexts.html">Log Contexts</a></li><li class="chapter-item expanded "><a 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(Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar"> <i class="fa fa-search"></i> </button> </div> <h1 class="menu-title">Synapse</h1> <div class="right-buttons"> <a href="../print.html" title="Print this book" aria-label="Print this book"> <i id="print-button" class="fa fa-print"></i> </a> <a href="https://github.com/matrix-org/synapse" title="Git repository" aria-label="Git repository"> <i id="git-repository-button" class="fa fa-github"></i> </a> <a href="https://github.com/matrix-org/synapse/edit/develop/docs/development/database_schema.md" title="Suggest an edit" aria-label="Suggest an edit"> <i id="git-edit-button" class="fa fa-edit"></i> </a> </div> </div> <div id="search-wrapper" class="hidden"> <form id="searchbar-outer" class="searchbar-outer"> <input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header"> </form> <div id="searchresults-outer" class="searchresults-outer hidden"> <div id="searchresults-header" class="searchresults-header"></div> <ul id="searchresults"> </ul> </div> </div> <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM --> <script type="text/javascript"> document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible'); document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible'); Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) { link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1); }); </script> <div id="content" class="content"> <main> <!-- Page table of contents --> <div class="sidetoc"> <nav class="pagetoc"></nav> </div> <h1 id="synapse-database-schema-files"><a class="header" href="#synapse-database-schema-files">Synapse database schema files</a></h1> <p>Synapse's database schema is stored in the <code>synapse.storage.schema</code> module.</p> <h2 id="logical-databases"><a class="header" href="#logical-databases">Logical databases</a></h2> <p>Synapse supports splitting its datastore across multiple physical databases (which can be useful for large installations), and the schema files are therefore split according to the logical database they apply to.</p> <p>At the time of writing, the following "logical" databases are supported:</p> <ul> <li><code>state</code> - used to store Matrix room state (more specifically, <code>state_groups</code>, their relationships and contents).</li> <li><code>main</code> - stores everything else.</li> </ul> <p>Additionally, the <code>common</code> directory contains schema files for tables which must be present on <em>all</em> physical databases.</p> <h2 id="synapse-schema-versions"><a class="header" href="#synapse-schema-versions">Synapse schema versions</a></h2> <p>Synapse manages its database schema via "schema versions". These are mainly used to help avoid confusion if the Synapse codebase is rolled back after the database is updated. They work as follows:</p> <ul> <li> <p>The Synapse codebase defines a constant <code>synapse.storage.schema.SCHEMA_VERSION</code> which represents the expectations made about the database by that version. For example, as of Synapse v1.36, this is <code>59</code>.</p> </li> <li> <p>The database stores a "compatibility version" in <code>schema_compat_version.compat_version</code> which defines the <code>SCHEMA_VERSION</code> of the oldest version of Synapse which will work with the database. On startup, if <code>compat_version</code> is found to be newer than <code>SCHEMA_VERSION</code>, Synapse will refuse to start.</p> <p>Synapse automatically updates this field from <code>synapse.storage.schema.SCHEMA_COMPAT_VERSION</code>.</p> </li> <li> <p>Whenever a backwards-incompatible change is made to the database format (normally via a <code>delta</code> file), <code>synapse.storage.schema.SCHEMA_COMPAT_VERSION</code> is also updated so that administrators can not accidentally roll back to a too-old version of Synapse.</p> </li> </ul> <p>Generally, the goal is to maintain compatibility with at least one or two previous releases of Synapse, so any substantial change tends to require multiple releases and a bit of forward-planning to get right.</p> <p>As a worked example: we want to remove the <code>room_stats_historical</code> table. Here is how it might pan out.</p> <ol> <li> <p>Replace any code that <em>reads</em> from <code>room_stats_historical</code> with alternative implementations, but keep writing to it in case of rollback to an earlier version. Also, increase <code>synapse.storage.schema.SCHEMA_VERSION</code>. In this instance, there is no existing code which reads from <code>room_stats_historical</code>, so our starting point is:</p> <p>v1.36.0: <code>SCHEMA_VERSION=59</code>, <code>SCHEMA_COMPAT_VERSION=59</code></p> </li> <li> <p>Next (say in Synapse v1.37.0): remove the code that <em>writes</em> to <code>room_stats_historical</code>, but don’t yet remove the table in case of rollback to v1.36.0. Again, we increase <code>synapse.storage.schema.SCHEMA_VERSION</code>, but because we have not broken compatibility with v1.36, we do not yet update <code>SCHEMA_COMPAT_VERSION</code>. We now have:</p> <p>v1.37.0: <code>SCHEMA_VERSION=60</code>, <code>SCHEMA_COMPAT_VERSION=59</code>.</p> </li> <li> <p>Later (say in Synapse v1.38.0): we can remove the table altogether. This will break compatibility with v1.36.0, so we must update <code>SCHEMA_COMPAT_VERSION</code> accordingly. There is no need to update <code>synapse.storage.schema.SCHEMA_VERSION</code>, since there is no change to the Synapse codebase here. So we end up with:</p> <p>v1.38.0: <code>SCHEMA_VERSION=60</code>, <code>SCHEMA_COMPAT_VERSION=60</code>.</p> </li> </ol> <p>If in doubt about whether to update <code>SCHEMA_VERSION</code> or not, it is generally best to lean towards doing so.</p> <h2 id="full-schema-dumps"><a class="header" href="#full-schema-dumps">Full schema dumps</a></h2> <p>In the <code>full_schemas</code> directories, only the most recently-numbered snapshot is used (<code>54</code> at the time of writing). Older snapshots (eg, <code>16</code>) are present for historical reference only.</p> <h3 id="building-full-schema-dumps"><a class="header" href="#building-full-schema-dumps">Building full schema dumps</a></h3> <p>If you want to recreate these schemas, they need to be made from a database that has had all background updates run.</p> <p>To do so, use <code>scripts-dev/make_full_schema.sh</code>. This will produce new <code>full.sql.postgres</code> and <code>full.sql.sqlite</code> files.</p> <p>Ensure postgres is installed, then run:</p> <pre><code>./scripts-dev/make_full_schema.sh -p postgres_username -o output_dir/ </code></pre> <p>NB at the time of writing, this script predates the split into separate <code>state</code>/<code>main</code> databases so will require updates to handle that correctly.</p> <h2 id="boolean-columns"><a class="header" href="#boolean-columns">Boolean columns</a></h2> <p>Boolean columns require special treatment, since SQLite treats booleans the same as integers.</p> <p>There are three separate aspects to this:</p> <ul> <li> <p>Any new boolean column must be added to the <code>BOOLEAN_COLUMNS</code> list in <code>scripts/synapse_port_db</code>. This tells the port script to cast the integer value from SQLite to a boolean before writing the value to the postgres database.</p> </li> <li> <p>Before SQLite 3.23, <code>TRUE</code> and <code>FALSE</code> were not recognised as constants by SQLite, and the <code>IS [NOT] TRUE</code>/<code>IS [NOT] FALSE</code> operators were not supported. This makes it necessary to avoid using <code>TRUE</code> and <code>FALSE</code> constants in SQL commands.</p> <p>For example, to insert a <code>TRUE</code> value into the database, write:</p> <pre><code class="language-python">txn.execute("INSERT INTO tbl(col) VALUES (?)", (True, )) </code></pre> </li> <li> <p>Default values for new boolean columns present a particular difficulty. Generally it is best to create separate schema files for Postgres and SQLite. For example:</p> <pre><code class="language-sql"># in 00delta.sql.postgres: ALTER TABLE tbl ADD COLUMN col BOOLEAN DEFAULT FALSE; </code></pre> <pre><code class="language-sql"># in 00delta.sql.sqlite: ALTER TABLE tbl ADD COLUMN col BOOLEAN DEFAULT 0; </code></pre> <p>Note that there is a particularly insidious failure mode here: the Postgres flavour will be accepted by SQLite 3.22, but will give a column whose default value is the <strong>string</strong> <code>"FALSE"</code> - which, when cast back to a boolean in Python, evaluates to <code>True</code>.</p> </li> </ul> </main> <nav class="nav-wrapper" aria-label="Page navigation"> <!-- Mobile navigation buttons --> <a rel="prev" href="../opentracing.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a rel="next" href="../development/experimental_features.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> <div style="clear: both"></div> </nav> </div> </div> <nav class="nav-wide-wrapper" aria-label="Page navigation"> <a rel="prev" href="../opentracing.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> <i class="fa fa-angle-left"></i> </a> <a rel="next" href="../development/experimental_features.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> <i class="fa fa-angle-right"></i> </a> </nav> </div> <script type="text/javascript"> window.playground_copyable = true; </script> <script src="../elasticlunr.min.js" type="text/javascript" charset="utf-8"></script> <script src="../mark.min.js" type="text/javascript" charset="utf-8"></script> <script src="../searcher.js" type="text/javascript" charset="utf-8"></script> <script src="../clipboard.min.js" type="text/javascript" charset="utf-8"></script> <script src="../highlight.js" type="text/javascript" charset="utf-8"></script> <script src="../book.js" type="text/javascript" charset="utf-8"></script> <!-- Custom JS scripts --> <script type="text/javascript" src="../docs/website_files/table-of-contents.js"></script> </body> </html>