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Remove pg_collation.collversion.

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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
This commit is contained in:
Thomas Munro
2020-11-02 19:36:09 +13:00
parent 8ef2a5afdf
commit 7d1297df08
22 changed files with 8 additions and 344 deletions
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11
doc/src/sgml/catalogs.sgml
View File

@@ -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>

6
doc/src/sgml/func.sgml
View File

@@ -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>

63
doc/src/sgml/ref/alter_collation.sgml
View File

@@ -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>

21
doc/src/sgml/ref/create_collation.sgml
View File

@@ -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>
@@ -149,26 +148,6 @@ CREATE COLLATION [ IF NOT EXISTS ] <replaceable>name</replaceable> FROM <replace
</listitem>
</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>