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Create the catalog infrastructure for foreign-data-wrapper handlers.

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Add a fdwhandler column to pg_foreign_data_wrapper, plus HANDLER options
in the CREATE FOREIGN DATA WRAPPER and ALTER FOREIGN DATA WRAPPER commands,
plus pg_dump support for same.  Also invent a new pseudotype fdw_handler
with properties similar to language_handler.

This is split out of the "FDW API" patch for ease of review; it's all stuff
we will certainly need, regardless of any other details of the FDW API.
FDW handler functions will not actually get called yet.

In passing, fix some omissions and infelicities in foreigncmds.c.

Shigeru Hanada, Jan Urbanski, Heikki Linnakangas
This commit is contained in:
Tom Lane
2011-02-19 00:06:18 -05:00
parent 4077980d67
commit 327e025071
22 changed files with 496 additions and 210 deletions
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50
doc/src/sgml/ref/create_foreign_data_wrapper.sgml
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@ -22,7 +22,8 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
CREATE FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable>
[ VALIDATOR <replaceable class="parameter">valfunction</replaceable> | NO VALIDATOR ]
[ HANDLER <replaceable class="parameter">handler_function</replaceable> | NO HANDLER ]
[ VALIDATOR <replaceable class="parameter">validator_function</replaceable> | NO VALIDATOR ]
[ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ... ] ) ]
</synopsis>
</refsynopsisdiv>
@ -59,13 +60,32 @@ CREATE FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable>
</varlistentry>
<varlistentry>
<term><literal>VALIDATOR <replaceable class="parameter">valfunction</replaceable></literal></term>
<term><literal>HANDLER <replaceable class="parameter">handler_function</replaceable></literal></term>
<listitem>
<para>
<replaceable class="parameter">valfunction</replaceable> is the
<replaceable class="parameter">handler_function</replaceable> is the
name of a previously registered function that will be called to
retrieve the execution functions for foreign tables.
The handler function must take no arguments, and
its return type must be <type>fdw_handler</type>.
</para>
<para>
It is possible to create a foreign-data wrapper with no handler
function, but foreign tables using such a wrapper can only be declared,
not accessed.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>VALIDATOR <replaceable class="parameter">validator_function</replaceable></literal></term>
<listitem>
<para>
<replaceable class="parameter">validator_function</replaceable> is the
name of a previously registered function that will be called to
check the generic options given to the foreign-data wrapper, as
well as to foreign servers and user mappings using the
well as options for foreign servers and user mappings using the
foreign-data wrapper. If no validator function or <literal>NO
VALIDATOR</literal> is specified, then options will not be
checked at creation time. (Foreign-data wrappers will possibly
@ -75,8 +95,8 @@ CREATE FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable>
contain the array of options as stored in the system catalogs,
and one of type <type>oid</type>, which will be the OID of the
system catalog containing the options. The return type is ignored;
the function should indicate invalid options using the
<function>ereport()</function> function.
the function should report invalid options using the
<function>ereport(ERROR)</function> function.
</para>
</listitem>
</varlistentry>
@ -87,8 +107,8 @@ CREATE FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable>
<para>
This clause specifies options for the new foreign-data wrapper.
The allowed option names and values are specific to each foreign
data wrapper and are validated using the foreign-data wrapper
library. Option names must be unique.
data wrapper and are validated using the foreign-data wrapper's
validator function. Option names must be unique.
</para>
</listitem>
</varlistentry>
@ -122,17 +142,17 @@ CREATE FOREIGN DATA WRAPPER <replaceable class="parameter">name</replaceable>
<title>Examples</title>
<para>
Create a foreign-data wrapper <literal>dummy</>:
Create a useless foreign-data wrapper <literal>dummy</>:
<programlisting>
CREATE FOREIGN DATA WRAPPER dummy;
</programlisting>
</para>
<para>
Create a foreign-data wrapper <literal>postgresql</> with
validator function <literal>postgresql_fdw_validator</>:
Create a foreign-data wrapper <literal>file</> with
handler function <literal>file_fdw_handler</>:
<programlisting>
CREATE FOREIGN DATA WRAPPER postgresql VALIDATOR postgresql_fdw_validator;
CREATE FOREIGN DATA WRAPPER file HANDLER file_fdw_handler;
</programlisting>
</para>
@ -151,10 +171,10 @@ CREATE FOREIGN DATA WRAPPER mywrapper
<para>
<command>CREATE FOREIGN DATA WRAPPER</command> conforms to ISO/IEC
9075-9 (SQL/MED), with the exception that
the <literal>VALIDATOR</literal> clause is an extension and the
9075-9 (SQL/MED), with the exception that the <literal>HANDLER</literal>
and <literal>VALIDATOR</literal> clauses are extensions and the standard
clauses <literal>LIBRARY</literal> and <literal>LANGUAGE</literal>
are not yet implemented in PostgreSQL.
are not implemented in PostgreSQL.
</para>
<para>