So I tried something else. I had a /etc/apache2/conf.d/mediawiki.conf with :
Alias /mediawiki /var/lib/mediawiki
<Directory /var/lib/mediawiki>
<Location /mediawiki> etc ...
Then today I created /etc/apache2/conf.d/mediawiki126.conf
Alias /mediawiki126 /opt/mediawiki-1.26.4
<Directory /opt/mediawiki-1.26.4/>
<Location /mediawiki126> etc ...
I deleted the old LocalSettings of MW 1.15 in /opt/mediawiki-1.26.4
Then I typed the URL https://localhost/mediawiki126 and set up the new configuration :
DbType : postgres
DbName : wikidb126
install account : postgres
DB account for web access : wikiuser (as before)
Admin account : WikiSysop (as before)
Ok the install has worked, but for the owner of the wikidb126 that I had to change despite the fact I specified wikiuser for db account, its owner will be postgres :
postgres=# \l
List of databases
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
postgres | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |
wikidb | wikiuser | UTF8 | en_US.UTF-8 | en_US.UTF-8 |
wikidb126 | postgres | UTF8 | en_US.UTF-8 | en_US.UTF-8 |
postgres=# alter database wikidb126 owner to wikiuser;
ALTER DATABASE
postgres=# \l
Name | Owner | Encoding | Collate | Ctype | Access privileges
-----------+----------+----------+-------------+-------------+-----------------------
wikidb | wikiuser | UTF8 | en_US.UTF-8 | en_US.UTF-8 |
wikidb126 | wikiuser | UTF8 | en_US.UTF-8 | en_US.UTF-8 |
postgres=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------+-----------
postgres | Superuser, Create role, Create DB, Replication | {}
wikiuser | | {}
After I change the db target : $wgDBname = "wikidb"; (instead of wikidb126, there are the 2 databases) and I start the update :
/opt/mediawiki-1.26.4/maintenance/# php update.php
MediaWiki 1.26.4 Updater
Your composer.lock file is up to date with current dependencies!
Going to run database updates for wikidb
Depending on the size of your database this may take a while!
Abort with control-c in the next five seconds (skip this countdown with --quick) ... 0
...index mwuser_pkey already set on mwuser table.
...index mwuser_user_name_key already set on mwuser table.
...index pagecontent_pkey already set on pagecontent table.
Renaming sequence ipblocks_ipb_id_val to ipblocks_ipb_id_seq
Renaming sequence rev_rev_id_val to revision_rev_id_seq
Renaming sequence text_old_id_val to text_old_id_seq
Renaming sequence rc_rc_id_seq to recentchanges_rc_id_seq
Renaming sequence log_log_id_seq to logging_log_id_seq
Renaming sequence pr_id_val to page_restrictions_pr_id_seq
Renaming sequence category_id_seq to category_cat_id_seq
Creating sequence archive_ar_id_seq
Creating sequence externallinks_el_id_seq
...category table already exists.
[..]
Altering column 'user_properties.up_user' to be DEFERRABLE INITIALLY DEFERRED
Altering column 'watchlist.wl_user' to be DEFERRABLE INITIALLY DEFERRED
Refreshing add_interwiki() ...A database query error has occurred.
Query: DROP FUNCTION IF EXISTS add_interwiki(TEXT,INT,CHARACTER) CASCADE
Function: DatabaseBase::sourceFile( /opt/mediawiki-1.26.4/maintenance/postgres/archives/patch-add_interwiki.sql )
Error: 42501 ERROR: must be owner of function add_interwiki
What's happen again ?