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diff --git a/doc/src/sgml/html/fdw-functions.html b/doc/src/sgml/html/fdw-functions.html new file mode 100644 index 0000000..ab19bdc --- /dev/null +++ b/doc/src/sgml/html/fdw-functions.html @@ -0,0 +1,36 @@ +<?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>59.1. Foreign Data Wrapper Functions</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="fdwhandler.html" title="Chapter 59. Writing a Foreign Data Wrapper" /><link rel="next" href="fdw-callbacks.html" title="59.2. Foreign Data Wrapper Callback Routines" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">59.1. Foreign Data Wrapper Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="fdwhandler.html" title="Chapter 59. Writing a Foreign Data Wrapper">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="fdwhandler.html" title="Chapter 59. Writing a Foreign Data Wrapper">Up</a></td><th width="60%" align="center">Chapter 59. Writing a Foreign Data Wrapper</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="fdw-callbacks.html" title="59.2. Foreign Data Wrapper Callback Routines">Next</a></td></tr></table><hr /></div><div class="sect1" id="FDW-FUNCTIONS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">59.1. Foreign Data Wrapper Functions</h2></div></div></div><p> + The FDW author needs to implement a handler function, and optionally + a validator function. Both functions must be written in a compiled + language such as C, using the version-1 interface. + For details on C language calling conventions and dynamic loading, + see <a class="xref" href="xfunc-c.html" title="38.10. C-Language Functions">Section 38.10</a>. + </p><p> + The handler function simply returns a struct of function pointers to + callback functions that will be called by the planner, executor, and + various maintenance commands. + Most of the effort in writing an FDW is in implementing these callback + functions. + The handler function must be registered with + <span class="productname">PostgreSQL</span> as taking no arguments and + returning the special pseudo-type <code class="type">fdw_handler</code>. The + callback functions are plain C functions and are not visible or + callable at the SQL level. The callback functions are described in + <a class="xref" href="fdw-callbacks.html" title="59.2. Foreign Data Wrapper Callback Routines">Section 59.2</a>. + </p><p> + The validator function is responsible for validating options given in + <code class="command">CREATE</code> and <code class="command">ALTER</code> commands for its + foreign data wrapper, as well as foreign servers, user mappings, and + foreign tables using the wrapper. + The validator function must be registered as taking two arguments, a + text array containing the options to be validated, and an OID + representing the type of object the options are associated with (in + the form of the OID of the system catalog the object would be stored + in, either + <code class="literal">ForeignDataWrapperRelationId</code>, + <code class="literal">ForeignServerRelationId</code>, + <code class="literal">UserMappingRelationId</code>, + or <code class="literal">ForeignTableRelationId</code>). + If no validator function is supplied, options are not checked at object + creation time or object alteration time. + </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="fdwhandler.html" title="Chapter 59. Writing a Foreign Data Wrapper">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="fdwhandler.html" title="Chapter 59. Writing a Foreign Data Wrapper">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="fdw-callbacks.html" title="59.2. Foreign Data Wrapper Callback Routines">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 59. Writing a Foreign Data Wrapper </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 59.2. Foreign Data Wrapper Callback Routines</td></tr></table></div></body></html>
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