[imp] Upgrading DB schemas

[R Phillips]

On 03/01/12 14:50, Michael J Rubinsky wrote:
> 
> Quoting R Phillips <R.I.Phillips at bath.ac.uk>:
> 
>> When upgrading minor versions, say from the Webmail groupware edition
>> from 4.0.3 to 4.0.5 there are some DB scheme changes.
>>
>> Is it possible to see whether those changes are significant, in that an
>> upgraded test install of horde/imp could be run against the same
>> database as a current live version?
>>
>> It's probably best to copy the existing database and run the test
>> version against the copy, but if the changes are limited to additional
>> database indexes/new columns then it would be possible without affecting
>> the live version.  Other than actually taking a copy and comparing after
>> upgrade, is there an easy way of comparing the old/new schema?
> 
> 
> If information in docs/UPGRADING or docs/CHANGES is not enough, you can
> look at the migration scripts to see what is being changed. e.g.,
> turba/migration contains the scripts that build all the tables and apply
> all the updates to the tables for Turba.


I did have a look at the migration folders, but was a bit puzzled.

To take specifics, I'm asked to upgrade the DB schema for
Horde_sessionhandler.

Looking at the script in migration folder I see:

    public function up()
    {
        if (!in_array('horde_sessionhandler', $this->tables())) {
            $t = $this->createTable('horde_sessionhandler',
array('autoincrementKey' => array('session_id')));

... snippped


which implies to me a create table, and not an upgrade so I'm slighly
puzzled.

The changes refer to a change in the SQL from REPLACE to an
INSERT/UPDATE, but not a schema change as far as I can see.

I suppose it's good practice not to test on a live database... so I'll
do that instead!