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>Chapter 50. Writing A Foreign Data Wrapper</H1
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>50.1. <A
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>Foreign Data Wrapper Functions</A
></DT
><DT
>50.2. <A
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>Foreign Data Wrapper Callback Routines</A
></DT
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>50.3. <A
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>Foreign Data Wrapper Helper Functions</A
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>Foreign Data Wrapper Query Planning</A
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> All operations on a foreign table are handled through its foreign data
wrapper, which consists of a set of functions that the core server
calls. The foreign data wrapper is responsible for fetching
data from the remote data source and returning it to the
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> executor. This chapter outlines how
to write a new foreign data wrapper.
</P
><P
> The foreign data wrappers included in the standard distribution are good
references when trying to write your own. Look into the
<TT
CLASS="FILENAME"
>contrib/file_fdw</TT
> subdirectory of the source tree.
The <A
HREF="sql-createforeigndatawrapper.html"
>CREATE FOREIGN DATA WRAPPER</A
> reference page also has
some useful details.
</P
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><B
>Note: </B
> The SQL standard specifies an interface for writing foreign data wrappers.
However, PostgreSQL does not implement that API, because the effort to
accommodate it into PostgreSQL would be large, and the standard API hasn't
gained wide adoption anyway.
</P
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