Re: remove wal_level archive

On Mon, Feb 8, 2016 at 6:47 AM, Peter Eisentraut <peter_e@gmx.net> wrote:
> On 1/26/16 10:56 AM, Simon Riggs wrote:
>> Removing one of "archive" or "hot standby" will just cause confusion and
>> breakage, so neither is a good choice for removal.
>>
>> What we should do is
>> 1. Map "archive" and "hot_standby" to one level with a new name that
>> indicates that it can be used for both/either backup or replication.
>>       (My suggested name for the new level is "replica"...)
>> 2. Deprecate "archive" and "hot_standby" so that those will be removed
>> in a later release.
>
> Updated patch to reflect these suggestions.

Shouldn't backup.sgml be updated as well? Here is the portion that I
am referring to:   To enable WAL archiving, set the <xref linkend="guc-wal-level">   configuration parameter to
<literal>archive</>or higher,   <xref linkend="guc-archive-mode"> to <literal>on</>,
 
        But minimal WAL does not contain enough information to reconstruct the
-        data from a base backup and the WAL logs, so <literal>archive</> or
+        data from a base backup and the WAL logs, so <literal>replica</> or        higher must be used to enable WAL
archiving       (<xref linkend="guc-archive-mode">) and streaming replication.       </para>       <para>
 
-        In <literal>hot_standby</> level, the same information is logged as
-        with <literal>archive</>, plus information needed to reconstruct
-        the status of running transactions from the WAL. To enable read-only
As the paragraph about the difference between hot_standby and archive
is removed, I think that it would be better to mention that setting
wal_level to replica allows to reconstruct data from a base backup and
the WAL logs, *and* to run read-only queries when hot_standby is
enabled.

-               if (ControlFile->wal_level < WAL_LEVEL_HOT_STANDBY)
+               if (ControlFile->wal_level < WAL_LEVEL_REPLICA)
Upthread it was mentioned that switching to an approach where enum
values are directly listed would be better. The target of an extra
patch on top of this one?

-       if (wal_level < WAL_LEVEL_ARCHIVE)
-               ereport(ERROR,
-
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-                                errmsg("replication slots can only be
used if wal_level >= archive")));
We should still forbid the creation of replication slots if wal_level = minimal.
-- 
Michael