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<title>42.6.pg_attrdef</title>
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="catalog-pg-attrdef"></a>42.6.<code class="structname">pg_attrdef</code></h2></div></div></div>
<a name="id821984"></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">
<a name="id822010"></a><p class="title"><b>Table42.6.<code class="structname">pg_attrdef</code> Columns</b></p>
<div class="table-contents"><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">adrelid</code></td>
<td><code class="type">oid</code></td>
<td><code class="literal"><a href="catalog-pg-class.html" title="42.12.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 href="catalog-pg-attribute.html" title="42.7.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">text</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.
</p>
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