Current File : //opt/alt/postgresql11/usr/share/doc/alt-postgresql11-9.2.24/html/fdw-helpers.html
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Foreign Data Wrapper Helper Functions</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REV="MADE"
HREF="mailto:pgsql-docs@postgresql.org"><LINK
REL="HOME"
TITLE="PostgreSQL 9.2.24 Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="Writing A Foreign Data Wrapper"
HREF="fdwhandler.html"><LINK
REL="PREVIOUS"
TITLE="Foreign Data Wrapper Callback Routines"
HREF="fdw-callbacks.html"><LINK
REL="NEXT"
TITLE="Foreign Data Wrapper Query Planning"
HREF="fdw-planning.html"><LINK
REL="STYLESHEET"
TYPE="text/css"
HREF="stylesheet.css"><META
HTTP-EQUIV="Content-Type"
CONTENT="text/html; charset=ISO-8859-1"><META
NAME="creation"
CONTENT="2017-11-06T22:43:11"></HEAD
><BODY
CLASS="SECT1"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="5"
ALIGN="center"
VALIGN="bottom"
><A
HREF="index.html"
>PostgreSQL 9.2.24 Documentation</A
></TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
TITLE="Foreign Data Wrapper Callback Routines"
HREF="fdw-callbacks.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="fdwhandler.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="60%"
ALIGN="center"
VALIGN="bottom"
>Chapter 50. Writing A Foreign Data Wrapper</TD
><TD
WIDTH="20%"
ALIGN="right"
VALIGN="top"
><A
TITLE="Foreign Data Wrapper Query Planning"
HREF="fdw-planning.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="FDW-HELPERS"
>50.3. Foreign Data Wrapper Helper Functions</A
></H1
><P
> Several helper functions are exported from the core server so that
authors of foreign data wrappers can get easy access to attributes of
FDW-related objects, such as FDW options.
To use any of these functions, you need to include the header file
<TT
CLASS="FILENAME"
>foreign/foreign.h</TT
> in your source file.
That header also defines the struct types that are returned by
these functions.
</P
><P
></P><PRE
CLASS="PROGRAMLISTING"
>ForeignDataWrapper *
GetForeignDataWrapper(Oid fdwid);</PRE
><P>
This function returns a <TT
CLASS="STRUCTNAME"
>ForeignDataWrapper</TT
>
object for the foreign-data wrapper with the given OID. A
<TT
CLASS="STRUCTNAME"
>ForeignDataWrapper</TT
> object contains properties
of the FDW (see <TT
CLASS="FILENAME"
>foreign/foreign.h</TT
> for details).
</P
><P
></P><PRE
CLASS="PROGRAMLISTING"
>ForeignServer *
GetForeignServer(Oid serverid);</PRE
><P>
This function returns a <TT
CLASS="STRUCTNAME"
>ForeignServer</TT
> object
for the foreign server with the given OID. A
<TT
CLASS="STRUCTNAME"
>ForeignServer</TT
> object contains properties
of the server (see <TT
CLASS="FILENAME"
>foreign/foreign.h</TT
> for details).
</P
><P
></P><PRE
CLASS="PROGRAMLISTING"
>UserMapping *
GetUserMapping(Oid userid, Oid serverid);</PRE
><P>
This function returns a <TT
CLASS="STRUCTNAME"
>UserMapping</TT
> object for
the user mapping of the given role on the given server. (If there is no
mapping for the specific user, it will return the mapping for
<TT
CLASS="LITERAL"
>PUBLIC</TT
>, or throw error if there is none.) A
<TT
CLASS="STRUCTNAME"
>UserMapping</TT
> object contains properties of the
user mapping (see <TT
CLASS="FILENAME"
>foreign/foreign.h</TT
> for details).
</P
><P
></P><PRE
CLASS="PROGRAMLISTING"
>ForeignTable *
GetForeignTable(Oid relid);</PRE
><P>
This function returns a <TT
CLASS="STRUCTNAME"
>ForeignTable</TT
> object for
the foreign table with the given OID. A
<TT
CLASS="STRUCTNAME"
>ForeignTable</TT
> object contains properties of the
foreign table (see <TT
CLASS="FILENAME"
>foreign/foreign.h</TT
> for details).
</P
><P
></P><PRE
CLASS="PROGRAMLISTING"
>List *
GetForeignColumnOptions(Oid relid, AttrNumber attnum);</PRE
><P>
This function returns the per-column FDW options for the column with the
given foreign table OID and attribute number, in the form of a list of
<TT
CLASS="STRUCTNAME"
>DefElem</TT
>. NIL is returned if the column has no
options.
</P
><P
> Some object types have name-based lookup functions in addition to the
OID-based ones:
</P
><P
></P><PRE
CLASS="PROGRAMLISTING"
>ForeignDataWrapper *
GetForeignDataWrapperByName(const char *name, bool missing_ok);</PRE
><P>
This function returns a <TT
CLASS="STRUCTNAME"
>ForeignDataWrapper</TT
>
object for the foreign-data wrapper with the given name. If the wrapper
is not found, return NULL if missing_ok is true, otherwise raise an
error.
</P
><P
></P><PRE
CLASS="PROGRAMLISTING"
>ForeignServer *
GetForeignServerByName(const char *name, bool missing_ok);</PRE
><P>
This function returns a <TT
CLASS="STRUCTNAME"
>ForeignServer</TT
> object
for the foreign server with the given name. If the server is not found,
return NULL if missing_ok is true, otherwise raise an error.
</P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="fdw-callbacks.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="fdw-planning.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Foreign Data Wrapper Callback Routines</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="fdwhandler.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Foreign Data Wrapper Query Planning</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
Mini Shell