Core support for "extensions", which are packages of SQL objects.

This patch adds the server infrastructure to support extensions.
There is still one significant loose end, namely how to make it play nice
with pg_upgrade, so I am not yet committing the changes that would make
all the contrib modules depend on this feature.

In passing, fix a disturbingly large amount of breakage in
AlterObjectNamespace() and callers.

Dimitri Fontaine, reviewed by Anssi Kääriäinen,
Itagaki Takahiro, Tom Lane, and numerous others

6 files changed, 354 insertions, 1 deletions

diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index c44d11ef91b..ba85cae0837 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -11,6 +11,7 @@ Complete list of usable sgml source files in this directory.
 <!entity alterDatabase      system "alter_database.sgml">
 <!entity alterDefaultPrivileges system "alter_default_privileges.sgml">
 <!entity alterDomain        system "alter_domain.sgml">
+<!entity alterExtension     system "alter_extension.sgml">
 <!entity alterForeignDataWrapper system "alter_foreign_data_wrapper.sgml">
 <!entity alterForeignTable  system "alter_foreign_table.sgml">
 <!entity alterFunction      system "alter_function.sgml">
@@ -50,6 +51,7 @@ Complete list of usable sgml source files in this directory.
 <!entity createConversion   system "create_conversion.sgml">
 <!entity createDatabase     system "create_database.sgml">
 <!entity createDomain       system "create_domain.sgml">
+<!entity createExtension    system "create_extension.sgml">
 <!entity createForeignDataWrapper system "create_foreign_data_wrapper.sgml">
 <!entity createForeignTable system "create_foreign_table.sgml">
 <!entity createFunction     system "create_function.sgml">
@@ -86,6 +88,7 @@ Complete list of usable sgml source files in this directory.
 <!entity dropConversion     system "drop_conversion.sgml">
 <!entity dropDatabase       system "drop_database.sgml">
 <!entity dropDomain         system "drop_domain.sgml">
+<!entity dropExtension      system "drop_extension.sgml">
 <!entity dropForeignDataWrapper system "drop_foreign_data_wrapper.sgml">
 <!entity dropForeignTable   system "drop_foreign_table.sgml">
 <!entity dropFunction       system "drop_function.sgml">
diff --git a/doc/src/sgml/ref/alter_extension.sgml b/doc/src/sgml/ref/alter_extension.sgml
new file mode 100644
index 00000000000..1b29d274cd6
--- /dev/null
+++ b/doc/src/sgml/ref/alter_extension.sgml
@@ -0,0 +1,98 @@
+<!--
+doc/src/sgml/ref/alter_extension.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-ALTEREXTENSION">
+ <refmeta>
+  <refentrytitle>ALTER EXTENSION</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>ALTER EXTENSION</refname>
+  <refpurpose>
+   change the definition of an extension
+  </refpurpose>
+ </refnamediv>
+
+ <indexterm zone="sql-alterextension">
+  <primary>ALTER EXTENSION</primary>
+ </indexterm>
+
+ <refsynopsisdiv>
+<synopsis>
+ALTER EXTENSION <replaceable class="PARAMETER">name</replaceable> SET SCHEMA <replaceable class="PARAMETER">new_schema</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>ALTER EXTENSION</command> changes the definition of an existing extension.
+   Currently there is only one subform:
+
+   <variablelist>
+   <varlistentry>
+    <term><literal>SET SCHEMA</literal></term>
+    <listitem>
+     <para>
+      This form moves the extension's objects into another schema. The
+      extension has to be <firstterm>relocatable</> for this command to
+      succeed. See <xref linkend="extend-extensions"> for details.
+     </para>
+    </listitem>
+   </varlistentry>
+   </variablelist>
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+   <para>
+    <variablelist>
+     <varlistentry>
+      <term><replaceable class="PARAMETER">name</replaceable></term>
+      <listitem>
+       <para>
+        The name of an installed extension.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><replaceable class="PARAMETER">new_schema</replaceable></term>
+      <listitem>
+       <para>
+        The new schema for the extension.
+       </para>
+      </listitem>
+     </varlistentry>
+    </variablelist>
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Examples</title>
+
+  <para>
+   To change the schema of the extension <literal>hstore</literal>
+   to <literal>utils</literal>:
+<programlisting>
+ALTER EXTENSION hstore SET SCHEMA utils;
+</programlisting>
+  </para>
+ </refsect1>
+
+ <refsect1 id="SQL-ALTEREXTENSION-see-also">
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createextension"></member>
+   <member><xref linkend="sql-dropextension"></member>
+  </simplelist>
+ </refsect1>
+</refentry>
diff --git a/doc/src/sgml/ref/comment.sgml b/doc/src/sgml/ref/comment.sgml
index f1a1605df3c..e1fe0c16f9a 100644
--- a/doc/src/sgml/ref/comment.sgml
+++ b/doc/src/sgml/ref/comment.sgml
@@ -31,6 +31,7 @@ COMMENT ON
   CONVERSION <replaceable class="PARAMETER">object_name</replaceable> |
   DATABASE <replaceable class="PARAMETER">object_name</replaceable> |
   DOMAIN <replaceable class="PARAMETER">object_name</replaceable> |
+  EXTENSION <replaceable class="PARAMETER">object_name</replaceable> |
   FOREIGN TABLE <replaceable class="PARAMETER">object_name</replaceable> |
   FUNCTION <replaceable class="PARAMETER">function_name</replaceable> ( [ [ <replaceable class="parameter">argmode</replaceable> ] [ <replaceable class="parameter">argname</replaceable> ] <replaceable class="parameter">argtype</replaceable> [, ...] ] ) |
   INDEX <replaceable class="PARAMETER">object_name</replaceable> |
diff --git a/doc/src/sgml/ref/create_extension.sgml b/doc/src/sgml/ref/create_extension.sgml
new file mode 100644
index 00000000000..961cab3839e
--- /dev/null
+++ b/doc/src/sgml/ref/create_extension.sgml
@@ -0,0 +1,118 @@
+<!--
+doc/src/sgml/ref/create_extension.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-CREATEEXTENSION">
+ <refmeta>
+  <refentrytitle>CREATE EXTENSION</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE EXTENSION</refname>
+  <refpurpose>install an extension</refpurpose>
+ </refnamediv>
+
+ <indexterm zone="sql-createextension">
+  <primary>CREATE EXTENSION</primary>
+ </indexterm>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE EXTENSION <replaceable class="parameter">extension_name</replaceable>
+    [ WITH ] [ SCHEMA [=] <replaceable class="parameter">schema</replaceable> ]
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE EXTENSION</command> loads a new extension into the current
+   database.  There must not be an extension of the same name already loaded.
+  </para>
+
+  <para>
+   Loading an extension essentially amounts to running the extension's script
+   file.  The script will typically create new <acronym>SQL</> objects such as
+   functions, data types, operators and index support methods.
+   <command>CREATE EXTENSION</command> additionally records the identities
+   of all the created objects, so that they can be dropped again if
+   <command>DROP EXTENSION</command> is issued.
+  </para>
+
+  <para>
+   For information about writing new extensions, see
+   <xref linkend="extend-extensions">.
+  </para>
+
+  <para>
+   Only superusers can execute <command>CREATE EXTENSION</command>.
+  </para>
+
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+    <variablelist>
+     <varlistentry>
+      <term><replaceable class="parameter">extension_name</replaceable></term>
+      <listitem>
+       <para>
+        The name of the extension to be
+        installed. <productname>PostgreSQL</productname> will create the
+        extension using details from the file
+        <literal>SHAREDIR/contrib/</literal><replaceable class="parameter">extension</replaceable><literal>.control</literal>.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
+      <term><replaceable class="parameter">schema</replaceable></term>
+      <listitem>
+       <para>
+        The name of the schema in which to install the extension's
+        objects, given that the extension allows its contents to be
+        relocated.  The named schema must already exist.
+        If not specified, and the extension's control file does not specify a
+        schema either, the current default object creation schema is used.
+       </para>
+      </listitem>
+     </varlistentry>
+  </variablelist>
+ </refsect1>
+
+ <refsect1>
+  <title>Examples</title>
+
+  <para>
+   Install the <link linkend="hstore">hstore</link> extension into the
+   current database:
+<programlisting>
+CREATE EXTENSION hstore;
+</programlisting>
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   <command>CREATE EXTENSION</command> is a <productname>PostgreSQL</>
+   extension.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-alterextension"></member>
+   <member><xref linkend="sql-dropextension"></member>
+  </simplelist>
+ </refsect1>
+
+</refentry>
diff --git a/doc/src/sgml/ref/drop_extension.sgml b/doc/src/sgml/ref/drop_extension.sgml
new file mode 100644
index 00000000000..1e09ec4c7a7
--- /dev/null
+++ b/doc/src/sgml/ref/drop_extension.sgml
@@ -0,0 +1,121 @@
+<!--
+doc/src/sgml/ref/drop_extension.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="SQL-DROPEXTENSION">
+ <refmeta>
+  <refentrytitle>DROP EXTENSION</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP EXTENSION</refname>
+  <refpurpose>remove an extension</refpurpose>
+ </refnamediv>
+
+ <indexterm zone="sql-dropextension">
+  <primary>DROP EXTENSION</primary>
+ </indexterm>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP EXTENSION [ IF EXISTS ] <replaceable class="PARAMETER">extension_name</replaceable> [, ...] [ CASCADE | RESTRICT ]
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>DROP EXTENSION</command> removes extensions from the database.
+   Dropping an extension causes its component objects to be dropped as well.
+  </para>
+
+  <para>
+   An extension can only be dropped by a superuser.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the extension does not exist. A notice is issued
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="PARAMETER">extension_name</replaceable></term>
+    <listitem>
+     <para>
+      The name of an installed extension.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><literal>CASCADE</literal></term>
+    <listitem>
+     <para>
+      Automatically drop objects that depend on the extension.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><literal>RESTRICT</literal></term>
+    <listitem>
+     <para>
+      Refuse to drop the extension if any objects depend on it (other than
+      its own member objects and other extensions listed in the same
+      <command>DROP</> command).  This is the default.
+     </para>
+    </listitem>
+   </varlistentry>
+  </variablelist>
+ </refsect1>
+
+ <refsect1>
+  <title>Examples</title>
+
+  <para>
+   To remove the extension <literal>hstore</literal> from the current
+   database:
+<programlisting>
+DROP EXTENSION hstore;
+</programlisting>
+   This command will fail if any of <literal>hstore</literal>'s objects
+   are in use in the database, for example if any tables have columns
+   of the <type>hstore</> type.  Add the <literal>CASCADE</> option to
+   forcibly remove those dependent objects as well.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   <command>DROP EXTENSION</command> is a <productname>PostgreSQL</>
+   extension.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createextension"></member>
+   <member><xref linkend="sql-alterextension"></member>
+  </simplelist>
+ </refsect1>
+
+</refentry>
diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index eacae71cdc7..cdf1abfa956 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -1357,7 +1357,6 @@ testdb=&gt;
         </listitem>
       </varlistentry>
 
-
       <varlistentry>
         <term><literal>\du[+] [ <link linkend="APP-PSQL-patterns"><replaceable class="parameter">pattern</replaceable></link> ]</literal></term>
         <listitem>
@@ -1371,6 +1370,19 @@ testdb=&gt;
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><literal>\dx[+] [ <link linkend="APP-PSQL-patterns"><replaceable class="parameter">pattern</replaceable></link> ]</literal></term>
+        <listitem>
+        <para>
+        Lists installed extensions.
+        If <replaceable class="parameter">pattern</replaceable>
+        is specified, only those extensions whose names match the pattern
+        are listed.
+        If the form <literal>\dx+</literal> is used, all the objects belonging
+        to each matching extension are listed.
+        </para>
+        </listitem>
+      </varlistentry>
 
       <varlistentry>
         <term><literal>\edit</> (or <literal>\e</>) <literal> <optional> <replaceable class="parameter">filename</> </optional> <optional> <replaceable class="parameter">line_number</> </optional> </literal></term>