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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>52.6. pg_attrdef</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="catalog-pg-amproc.html" title="52.5. pg_amproc" /><link rel="next" href="catalog-pg-attribute.html" title="52.7. pg_attribute" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">52.6. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_attrdef</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-amproc.html" title="52.5. pg_amproc">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="catalogs.html" title="Chapter 52. System Catalogs">Up</a></td><th width="60%" align="center">Chapter 52. System Catalogs</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="catalog-pg-attribute.html" title="52.7. pg_attribute">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="CATALOG-PG-ATTRDEF"><div class="titlepage"><div><div><h2 class="title" style="clear: both">52.6. <code class="structname">pg_attrdef</code></h2></div></div></div><a id="id-1.10.4.8.2" class="indexterm"></a><p>
The catalog <code class="structname">pg_attrdef</code> stores column default values. The main information
about columns is stored in <code class="structname">pg_attribute</code>
(see below). Only columns that explicitly specify a default value
(when the table is created or the column is added) will have an
entry here.
</p><div class="table" id="id-1.10.4.8.4"><p class="title"><strong>Table 52.6. <code class="structname">pg_attrdef</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_attrdef Columns" border="1"><colgroup><col /><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Type</th><th>References</th><th>Description</th></tr></thead><tbody><tr><td><code class="structfield">oid</code></td><td><code class="type">oid</code></td><td> </td><td>Row identifier (hidden attribute; must be explicitly selected)</td></tr><tr><td><code class="structfield">adrelid</code></td><td><code class="type">oid</code></td><td><code class="literal"><a class="link" href="catalog-pg-class.html" title="52.11. pg_class"><code class="structname">pg_class</code></a>.oid</code></td><td>The table this column belongs to</td></tr><tr><td><code class="structfield">adnum</code></td><td><code class="type">int2</code></td><td><code class="literal"><a class="link" href="catalog-pg-attribute.html" title="52.7. pg_attribute"><code class="structname">pg_attribute</code></a>.attnum</code></td><td>The number of the column</td></tr><tr><td><code class="structfield">adbin</code></td><td><code class="type">pg_node_tree</code></td><td> </td><td>The internal representation of the column default value</td></tr><tr><td><code class="structfield">adsrc</code></td><td><code class="type">text</code></td><td> </td><td>A human-readable representation of the default value</td></tr></tbody></table></div></div><br class="table-break" /><p>
The <code class="structfield">adsrc</code> field is historical, and is best
not used, because it does not track outside changes that might affect
the representation of the default value. Reverse-compiling the
<code class="structfield">adbin</code> field (with <code class="function">pg_get_expr</code> for
example) is a better way to display the default value.
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