Remove pg_collation.collversion.

This model couldn't be extended to cover the default collation, and
didn't have any information about the affected database objects when the
version changed.  Remove, in preparation for a follow-up commit that
will add a new mechanism.

Author: Thomas Munro <thomas.munro@gmail.com>
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Discussion: https://postgr.es/m/CAEepm%3D0uEQCpfq_%2BLYFBdArCe4Ot98t1aR4eYiYTe%3DyavQygiQ%40mail.gmail.com

4 files changed, 1 insertions, 100 deletions

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 0ccdff1cda6..d0d2598290e 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -2361,17 +2361,6 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
        <symbol>LC_CTYPE</symbol> for this collation object
       </para></entry>
      </row>
-
-     <row>
-      <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>collversion</structfield> <type>text</type>
-      </para>
-      <para>
-       Provider-specific version of the collation.  This is recorded when the
-       collation is created and then checked when it is used, to detect
-       changes in the collation definition that could lead to data corruption.
-      </para></entry>
-     </row>
     </tbody>
    </tgroup>
   </table>
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index d8eee3a8264..0398b4909bf 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -25444,11 +25444,7 @@ postgres=# SELECT * FROM pg_walfile_name_offset(pg_stop_backup());
        </para>
        <para>
         Returns the actual version of the collation object as it is currently
-        installed in the operating system.  If this is different from the
-        value in
-        <structname>pg_collation</structname>.<structfield>collversion</structfield>,
-        then objects depending on the collation might need to be rebuilt.  See
-        also <xref linkend="sql-altercollation"/>.
+        installed in the operating system.
        </para></entry>
       </row>
 
diff --git a/doc/src/sgml/ref/alter_collation.sgml b/doc/src/sgml/ref/alter_collation.sgml
index af9ff2867b7..65429aabe28 100644
--- a/doc/src/sgml/ref/alter_collation.sgml
+++ b/doc/src/sgml/ref/alter_collation.sgml
@@ -21,8 +21,6 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-ALTER COLLATION <replaceable>name</replaceable> REFRESH VERSION
-
 ALTER COLLATION <replaceable>name</replaceable> RENAME TO <replaceable>new_name</replaceable>
 ALTER COLLATION <replaceable>name</replaceable> OWNER TO { <replaceable>new_owner</replaceable> | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
 ALTER COLLATION <replaceable>name</replaceable> SET SCHEMA <replaceable>new_schema</replaceable>
@@ -88,70 +86,9 @@ ALTER COLLATION <replaceable>name</replaceable> SET SCHEMA <replaceable>new_sche
     </listitem>
    </varlistentry>
 
-   <varlistentry>
-    <term><literal>REFRESH VERSION</literal></term>
-    <listitem>
-     <para>
-      Update the collation's version.
-      See <xref linkend="sql-altercollation-notes"/> below.
-     </para>
-    </listitem>
-   </varlistentry>
   </variablelist>
  </refsect1>
 
- <refsect1 id="sql-altercollation-notes" xreflabel="Notes">
-  <title>Notes</title>
-
-  <para>
-   When using collations provided by the ICU library, the ICU-specific version
-   of the collator is recorded in the system catalog when the collation object
-   is created.  When the collation is used, the current version is
-   checked against the recorded version, and a warning is issued when there is
-   a mismatch, for example:
-<screen>
-WARNING:  collation "xx-x-icu" has version mismatch
-DETAIL:  The collation in the database was created using version 1.2.3.4, but the operating system provides version 2.3.4.5.
-HINT:  Rebuild all objects affected by this collation and run ALTER COLLATION pg_catalog."xx-x-icu" REFRESH VERSION, or build PostgreSQL with the right library version.
-</screen>
-   A change in collation definitions can lead to corrupt indexes and other
-   problems because the database system relies on stored objects having a
-   certain sort order.  Generally, this should be avoided, but it can happen
-   in legitimate circumstances, such as when
-   using <command>pg_upgrade</command> to upgrade to server binaries linked
-   with a newer version of ICU.  When this happens, all objects depending on
-   the collation should be rebuilt, for example,
-   using <command>REINDEX</command>.  When that is done, the collation version
-   can be refreshed using the command <literal>ALTER COLLATION ... REFRESH
-   VERSION</literal>.  This will update the system catalog to record the
-   current collator version and will make the warning go away.  Note that this
-   does not actually check whether all affected objects have been rebuilt
-   correctly.
-  </para>
-  <para>
-   When using collations provided by <literal>libc</literal> and
-   <productname>PostgreSQL</productname> was built with the GNU C library, the
-   C library's version is used as a collation version.  Since collation
-   definitions typically change only with GNU C library releases, this provides
-   some defense against corruption, but it is not completely reliable.
-  </para>
-  <para>
-   Currently, there is no version tracking for the database default collation.
-  </para>
-
-  <para>
-   The following query can be used to identify all collations in the current
-   database that need to be refreshed and the objects that depend on them:
-<programlisting><![CDATA[
-SELECT pg_describe_object(refclassid, refobjid, refobjsubid) AS "Collation",
-       pg_describe_object(classid, objid, objsubid) AS "Object"
-  FROM pg_depend d JOIN pg_collation c
-       ON refclassid = 'pg_collation'::regclass AND refobjid = c.oid
-  WHERE c.collversion <> pg_collation_actual_version(c.oid)
-  ORDER BY 1, 2;
-]]></programlisting></para>
- </refsect1>
-
  <refsect1>
   <title>Examples</title>
 
diff --git a/doc/src/sgml/ref/create_collation.sgml b/doc/src/sgml/ref/create_collation.sgml
index 58f5f0cd63a..b97842071f9 100644
--- a/doc/src/sgml/ref/create_collation.sgml
+++ b/doc/src/sgml/ref/create_collation.sgml
@@ -27,7 +27,6 @@ CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> (
     [ LC_CTYPE = <replaceable>lc_ctype</replaceable>, ]
     [ PROVIDER = <replaceable>provider</replaceable>, ]
     [ DETERMINISTIC = <replaceable>boolean</replaceable>, ]
-    [ VERSION = <replaceable>version</replaceable> ]
 )
 CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replaceable>existing_collation</replaceable>
 </synopsis>
@@ -150,26 +149,6 @@ CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replace
     </varlistentry>
 
     <varlistentry>
-     <term><replaceable>version</replaceable></term>
-
-     <listitem>
-      <para>
-       Specifies the version string to store with the collation.  Normally,
-       this should be omitted, which will cause the version to be computed
-       from the actual version of the collation as provided by the operating
-       system.  This option is intended to be used
-       by <command>pg_upgrade</command> for copying the version from an
-       existing installation.
-      </para>
-
-      <para>
-       See also <xref linkend="sql-altercollation"/> for how to handle
-       collation version mismatches.
-      </para>
-     </listitem>
-    </varlistentry>
-
-    <varlistentry>
      <term><replaceable>existing_collation</replaceable></term>
 
      <listitem>