<sect2>

<title>Remote Query Execution Environment</title>

<para>

In the remote sessions opened by <filename>postgres_fdw</>,

the <xref linkend="guc-search-path"> parameter is set to

just <literal>pg_catalog</>, so that only built-in objects are visible

without schema qualification. This is not an issue for queries

generated by <filename>postgres_fdw</> itself, because it always

supplies such qualification. However, this can pose a hazard for

functions that are executed on the remote server via triggers or rules

on remote tables. For example, if a remote table is actually a view,

any functions used in that view will be executed with the restricted

search path. It is recommended to schema-qualify all names in such

functions, or else attach <literal>SET search_path</> options

(see <xref linkend="sql-createfunction">) to such functions

to establish their expected search path environment.

</para>

<para>

<filename>postgres_fdw</> likewise establishes remote session settings

for the parameters <xref linkend="guc-timezone">,

<xref linkend="guc-datestyle">, <xref linkend="guc-intervalstyle">,

and <xref linkend="guc-extra-float-digits">. These are less likely

to be problematic than <varname>search_path</>, but can be handled

with function <literal>SET</> options if the need arises.

</para>

<para>

It is <emphasis>not</> recommended that you override this behavior by

changing the session-level settings of these parameters; that is likely

to cause <filename>postgres_fdw</> to malfunction.

</para>

</sect2>