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Rearrange extension-related views as per recent discussion.
The original design of pg_available_extensions did not consider the possibility of version-specific control files. Split it into two views: pg_available_extensions shows information that is generic about an extension, while pg_available_extension_versions shows all available versions together with information that could be version-dependent. Also, add an SRF pg_extension_update_paths() to assist in checking that a collection of update scripts provide sane update path sequences.
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‎doc/src/sgml/catalogs.sgml

Lines changed: 82 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -6330,6 +6330,11 @@
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<entry>available extensions</entry>
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</row>
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<row>
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<entry><link linkend="view-pg-available-extension-versions"><structname>pg_available_extension_versions</structname></link></entry>
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<entry>available versions of extensions</entry>
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</row>
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<row>
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<entry><link linkend="view-pg-cursors"><structname>pg_cursors</structname></link></entry>
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<entry>open cursors</entry>
@@ -6460,23 +6465,78 @@
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</row>
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<row>
6463-
<entry><structfield>version</structfield></entry>
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<entry><structfield>default_version</structfield></entry>
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<entry><type>text</type></entry>
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<entry>Version string from the extension's control file</entry>
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<entry>Name of default version, or <literal>NULL</literal> if none is
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specified</entry>
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</row>
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<row>
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<entry><structfield>installed</structfield></entry>
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<entry><structfield>installed_version</structfield></entry>
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<entry><type>text</type></entry>
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<entry>Currently installed version of the extension,
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or <literal>NULL</literal> if not installed</entry>
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</row>
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<row>
6476-
<entry><structfield>schema</structfield></entry>
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<entry><structfield>comment</structfield></entry>
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<entry><type>text</type></entry>
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<entry>Comment string from the extension's control file</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<para>
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The <structname>pg_available_extensions</structname> view is read only.
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</para>
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</sect1>
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<sect1 id="view-pg-available-extension-versions">
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<title><structname>pg_available_extension_versions</structname></title>
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<indexterm zone="view-pg-available-extension-versions">
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<primary>pg_available_extension_versions</primary>
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</indexterm>
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<para>
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The <structname>pg_available_extension_versions</structname> view lists the
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specific extension versions that are available for installation. This view
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can only be read by superusers. See also the <link
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linkend="catalog-pg-extension"><structname>pg_extension</structname></link>
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catalog, which shows the extensions currently installed.
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</para>
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<table>
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<title><structname>pg_available_extension_versions</> Columns</title>
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<tgroup cols="3">
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<thead>
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<row>
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<entry>Name</entry>
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<entry>Type</entry>
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<entry>Description</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><structfield>name</structfield></entry>
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<entry><type>name</type></entry>
6478-
<entry>Name of the schema where the extension is installed,
6479-
or <literal>NULL</literal> if not installed</entry>
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<entry>Extension name</entry>
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</row>
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<row>
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<entry><structfield>version</structfield></entry>
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<entry><type>text</type></entry>
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<entry>Version name</entry>
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</row>
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<row>
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<entry><structfield>installed</structfield></entry>
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<entry><type>bool</type></entry>
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<entry>True if this version of this extension is currently
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installed</entry>
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</row>
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<row>
@@ -6485,6 +6545,20 @@
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<entry>True if extension can be relocated to another schema</entry>
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</row>
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<row>
6549+
<entry><structfield>schema</structfield></entry>
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<entry><type>name</type></entry>
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<entry>Name of the schema that the extension must be installed into,
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or <literal>NULL</literal> if partially or fully relocatable</entry>
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</row>
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6555+
<row>
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<entry><structfield>requires</structfield></entry>
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<entry><type>name[]</type></entry>
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<entry>Names of prerequisite extensions,
6559+
or <literal>NULL</literal> if none</entry>
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</row>
6561+
64886562
<row>
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<entry><structfield>comment</structfield></entry>
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<entry><type>text</type></entry>
@@ -6495,9 +6569,9 @@
64956569
</table>
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64976571
<para>
6498-
The <structname>pg_available_extensions</structname> view is read only.
6572+
The <structname>pg_available_extension_versions</structname> view is read
6573+
only.
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</para>
6500-
65016575
</sect1>
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65036577
<sect1 id="view-pg-cursors">

‎doc/src/sgml/extend.sgml

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -765,6 +765,20 @@ SELECT pg_catalog.pg_extension_config_dump('my_config', 'WHERE NOT standard_entr
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path than to move ahead one version at a time. If the downgrade script
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drops any irreplaceable objects, this will yield undesirable results.
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</para>
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769+
<para>
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To check for unexpected update paths, use this command:
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<programlisting>
772+
SELECT * FROM pg_extension_update_paths('<replaceable>extension_name</>');
773+
</programlisting>
774+
This shows each pair of distinct known version names for the specified
775+
extension, together with the update path sequence that would be taken to
776+
get from the source version to the target version, or <literal>NULL</> if
777+
there is no available update path. The path is shown in textual form
778+
with <literal>--</> separators. You can use
779+
<literal>regexp_split_to_array(path,'--')</> if you prefer an array
780+
format.
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</para>
768782
</sect2>
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<sect2>

‎src/backend/catalog/system_views.sql

Lines changed: 10 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -154,11 +154,17 @@ CREATE VIEW pg_cursors AS
154154
SELECT * FROM pg_cursor() AS C;
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156156
CREATE VIEW pg_available_extensions AS
157-
SELECT E.name, E.version, X.extversion AS installed,
158-
N.nspname AS schema, E.relocatable, E.comment
157+
SELECT E.name, E.default_version, X.extversion AS installed_version,
158+
E.comment
159159
FROM pg_available_extensions() AS E
160-
LEFT JOIN pg_extension AS X ON E.name = X.extname
161-
LEFT JOIN pg_namespace AS N on N.oid = X.extnamespace;
160+
LEFT JOIN pg_extension AS X ON E.name = X.extname;
161+
162+
CREATE VIEW pg_available_extension_versions AS
163+
SELECT E.name, E.version, (X.extname IS NOT NULL) AS installed,
164+
E.relocatable, E.schema, E.requires, E.comment
165+
FROM pg_available_extension_versions() AS E
166+
LEFT JOIN pg_extension AS X
167+
ON E.name = X.extname AND E.version = X.extversion;
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163169
CREATE VIEW pg_prepared_xacts AS
164170
SELECT P.transaction, P.gid, P.prepared,

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