Adding upstream version 13.4.upstream/13.4 upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
author: Daniel Baumann <daniel.baumann@progress-linux.org> 2024-05-04 12:19:15 +0000
committer: Daniel Baumann <daniel.baumann@progress-linux.org> 2024-05-04 12:19:15 +0000
commit: 6eb9c5a5657d1fe77b55cc261450f3538d35a94d (patch)
tree: 657d8194422a5daccecfd42d654b8a245ef7b4c8 /doc/src/sgml/html/catalog-pg-cast.html
parent: Initial commit. (diff)
download: postgresql-13-upstream.tar.xz
postgresql-13-upstream.zip
1 files changed, 86 insertions, 0 deletions
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+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!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>51.10. pg_cast</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 V1.79.1" /><link rel="prev" href="catalog-pg-auth-members.html" title="51.9. pg_auth_members" /><link rel="next" href="catalog-pg-class.html" title="51.11. pg_class" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">51.10. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_cast</code></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="catalog-pg-auth-members.html" title="51.9. pg_auth_members">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="catalogs.html" title="Chapter 51. System Catalogs">Up</a></td><th width="60%" align="center">Chapter 51. System Catalogs</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="catalog-pg-class.html" title="51.11. pg_class">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="CATALOG-PG-CAST"><div class="titlepage"><div><div><h2 class="title" style="clear: both">51.10. <code class="structname">pg_cast</code></h2></div></div></div><a id="id-1.10.4.12.2" class="indexterm"></a><p>
+   The catalog <code class="structname">pg_cast</code> stores data type conversion
+   paths, both built-in and user-defined.
+  </p><p>
+   It should be noted that <code class="structname">pg_cast</code> does not represent
+   every type conversion that the system knows how to perform; only those that
+   cannot be deduced from some generic rule.  For example, casting between a
+   domain and its base type is not explicitly represented in
+   <code class="structname">pg_cast</code>.  Another important exception is that
+   <span class="quote">“<span class="quote">automatic I/O conversion casts</span>”</span>, those performed using a data
+   type's own I/O functions to convert to or from <code class="type">text</code> or other
+   string types, are not explicitly represented in
+   <code class="structname">pg_cast</code>.
+  </p><div class="table" id="id-1.10.4.12.5"><p class="title"><strong>Table 51.10. <code class="structname">pg_cast</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_cast Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
+       Column Type
+      </p>
+      <p>
+       Description
+      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
+       <code class="structfield">oid</code> <code class="type">oid</code>
+      </p>
+      <p>
+       Row identifier
+      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
+       <code class="structfield">castsource</code> <code class="type">oid</code>
+       (references <a class="link" href="catalog-pg-type.html" title="51.62. pg_type"><code class="structname">pg_type</code></a>.<code class="structfield">oid</code>)
+      </p>
+      <p>
+       OID of the source data type
+      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
+       <code class="structfield">casttarget</code> <code class="type">oid</code>
+       (references <a class="link" href="catalog-pg-type.html" title="51.62. pg_type"><code class="structname">pg_type</code></a>.<code class="structfield">oid</code>)
+      </p>
+      <p>
+       OID of the target data type
+      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
+       <code class="structfield">castfunc</code> <code class="type">oid</code>
+       (references <a class="link" href="catalog-pg-proc.html" title="51.38. pg_proc"><code class="structname">pg_proc</code></a>.<code class="structfield">oid</code>)
+      </p>
+      <p>
+       The OID of the function to use to perform this cast.  Zero is
+       stored if the cast method doesn't require a function.
+      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
+       <code class="structfield">castcontext</code> <code class="type">char</code>
+      </p>
+      <p>
+       Indicates what contexts the cast can be invoked in.
+       <code class="literal">e</code> means only as an explicit cast (using
+       <code class="literal">CAST</code> or <code class="literal">::</code> syntax).
+       <code class="literal">a</code> means implicitly in assignment
+       to a target column, as well as explicitly.
+       <code class="literal">i</code> means implicitly in expressions, as well as the
+       other cases.
+      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
+       <code class="structfield">castmethod</code> <code class="type">char</code>
+      </p>
+      <p>
+       Indicates how the cast is performed.
+       <code class="literal">f</code> means that the function specified in the <code class="structfield">castfunc</code> field is used.
+       <code class="literal">i</code> means that the input/output functions are used.
+       <code class="literal">b</code> means that the types are binary-coercible, thus no conversion is required.
+      </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
+   The cast functions listed in <code class="structname">pg_cast</code> must
+   always take the cast source type as their first argument type, and
+   return the cast destination type as their result type.  A cast
+   function can have up to three arguments.  The second argument,
+   if present, must be type <code class="type">integer</code>; it receives the type
+   modifier associated with the destination type, or -1
+   if there is none.  The third argument,
+   if present, must be type <code class="type">boolean</code>; it receives <code class="literal">true</code>
+   if the cast is an explicit cast, <code class="literal">false</code> otherwise.
+  </p><p>
+   It is legitimate to create a <code class="structname">pg_cast</code> entry
+   in which the source and target types are the same, if the associated
+   function takes more than one argument.  Such entries represent
+   <span class="quote">“<span class="quote">length coercion functions</span>”</span> that coerce values of the type
+   to be legal for a particular type modifier value.
+  </p><p>
+   When a <code class="structname">pg_cast</code> entry has different source and
+   target types and a function that takes more than one argument, it
+   represents converting from one type to another and applying a length
+   coercion in a single step.  When no such entry is available, coercion
+   to a type that uses a type modifier involves two steps, one to
+   convert between data types and a second to apply the modifier.
+  </p></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-auth-members.html" title="51.9. pg_auth_members">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="catalogs.html" title="Chapter 51. System Catalogs">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="catalog-pg-class.html" title="51.11. pg_class">Next</a></td></tr><tr><td width="40%" align="left" valign="top">51.9. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_auth_members</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 51.11. <code xmlns="http://www.w3.org/1999/xhtml" class="structname">pg_class</code></td></tr></table></div></body></html>
+\ No newline at end of file
author	Daniel Baumann <daniel.baumann@progress-linux.org>	2024-05-04 12:19:15 +0000
committer	Daniel Baumann <daniel.baumann@progress-linux.org>	2024-05-04 12:19:15 +0000
commit	6eb9c5a5657d1fe77b55cc261450f3538d35a94d (patch)
tree	657d8194422a5daccecfd42d654b8a245ef7b4c8 /doc/src/sgml/html/catalog-pg-cast.html
parent	Initial commit. (diff)
download	postgresql-13-upstream.tar.xz postgresql-13-upstream.zip