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Allow default expressions to be attached to columns of foreign tables.

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There's still some discussion about exactly how postgres_fdw ought to
handle this case, but there seems no debate that we want to allow defaults
to be used for inserts into foreign tables.  So remove the core-code
restrictions that prevented it.

While at it, get rid of the special grammar productions for CREATE FOREIGN
TABLE, and instead add explicit FEATURE_NOT_SUPPORTED error checks for the
disallowed cases.  This makes the grammar a shade smaller, and more
importantly results in much more intelligible error messages for
unsupported cases.  It's also one less thing to fix if we ever start
supporting constraints on foreign tables.
This commit is contained in:
Tom Lane
2013-03-12 17:37:07 -04:00
parent 1ba0119308
commit a0c6dfeecf
7 changed files with 123 additions and 64 deletions
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31
doc/src/sgml/ref/create_foreign_table.sgml
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@@ -19,12 +19,18 @@
<refsynopsisdiv>
<synopsis>
CREATE FOREIGN TABLE [ IF NOT EXISTS ] <replaceable class="PARAMETER">table_name</replaceable> ( [
{ <replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ... ] ) ] [ NULL | NOT NULL ] }
<replaceable class="PARAMETER">column_name</replaceable> <replaceable class="PARAMETER">data_type</replaceable> [ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ... ] ) ] [ COLLATE <replaceable>collation</replaceable> ] [ <replaceable class="PARAMETER">column_constraint</replaceable> [ ... ] ]
[, ... ]
] )
SERVER <replaceable class="parameter">server_name</replaceable>
[ OPTIONS ( <replaceable class="PARAMETER">option</replaceable> '<replaceable class="PARAMETER">value</replaceable>' [, ... ] ) ]
<phrase>where <replaceable class="PARAMETER">column_constraint</replaceable> is:</phrase>
[ CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> ]
{ NOT NULL |
NULL |
DEFAULT <replaceable>default_expr</replaceable> }
</synopsis>
</refsynopsisdiv>
@@ -131,6 +137,27 @@ CREATE FOREIGN TABLE [ IF NOT EXISTS ] <replaceable class="PARAMETER">table_name
</listitem>
</varlistentry>
<varlistentry>
<term><literal>DEFAULT
<replaceable>default_expr</replaceable></literal></term>
<listitem>
<para>
The <literal>DEFAULT</> clause assigns a default data value for
the column whose column definition it appears within. The value
is any variable-free expression (subqueries and cross-references
to other columns in the current table are not allowed). The
data type of the default expression must match the data type of the
column.
</para>
<para>
The default expression will be used in any insert operation that
does not specify a value for the column. If there is no default
for a column, then the default is null.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">server_name</replaceable></term>
<listitem>
@@ -190,6 +217,8 @@ SERVER film_server;
<acronym>SQL</acronym> standard; however, much as with
<link linkend="sql-createtable"><command>CREATE TABLE</></link>,
<literal>NULL</> constraints and zero-column foreign tables are permitted.
The ability to specify a default value is also a <productname>PostgreSQL</>
extension.
</para>
</refsect1>