Hi,
On 12/12/12 5:31 PM, Gary Martin wrote:
On 12/12/12 15:18, Jure Zitnik wrote:
2. Something that we might forgot: What about 3rd party plugin
tables that
reference multiproductized Trac tables?
Will probably need to proclaim these incompatible when more
than one
product is in effect?
Good point. To keep track of records from tables from third party
plugins, this approach doesn't quite work. I would have thought that
we would be better off using a separate table to keep track of the
resources that belong to a product. Is this another area that has
not been updated based on discussions?
The current SQL translator implementation would show 3rd party
plugins a view of translated tables that would only include resources
from the currently selected product scope. If the plugin makes a
reference to a resource by it's name everything should work fine as
the reference would be consistent each time when in that specific
product environment (as the plugin would always get the same view of
the database).
Things start breaking if there's a resource with the same name in
multiple products, unless the translator is changed to return names
with product namespace being prefixed to the actual resource name for
example. The plugins would get version name 'BH:1.0' instead of '1.0'
for example. Still, this doesn't solve the problem entirely as the
plugin (that's not aware of products) would end up (in it's own
tables) with references to different resources from different
products and maybe that's not exactly what's expected to happen...
Keeping track of resource belonging to a product using a separate
resource mapping table also unfortunately doesn't solve the issue.
We'd need to change the schema anyway as in the current database
model, all tables have 'name' column as their key. We could of course
reference the same resource from different products using the
separate mapping table but we'd be referencing the same record and
changing the name of that record would change the resource in all
products which is, at least imo, not what we want.
Ah yes, I forgot about my ideas for that. For the purposes of unique
keys I was thinking of including some kind of prefix as part of the
name - not necessarily the product namespace as we could consider it
better to leave this as a constant with a means to link the prefix to
the namespace.
As I wrote above, only prefixing names doesn't solve the issue. If we
have a product unaware plugin, that plugin should only see resources
from the current product scope and this (for trac/bh resources) is
currently accomplished by translating SQLs in such a way that the plugin
only sees a product specific view of resources. The problem arises when
the plugin stores references to that resources in their own tables as it
might end up (unless we do something about it) with resource mixed from
different products.
Let's say we have a custom table named 'sorted_milestones' with columns
'milestone_name' and 'sequence' and database constraint that 'sequence'
is unique. If plugins sees only resources (in this case milestones) from
one product at a time, constraint will fail as logic sees only product
scope specific part of milestones. When product scope would change, the
plugin sees completely different set of milestones and has no way of
knowing that certain sequences are already 'taken'.
On the other hand, assuming we only prefix resources without filtering
them for multi-product unaware plugins would cause the user interface
for those plugins to show everything (every resource defined regardless
of product scope). In addition to that, it'd be hard (if not impossible)
to remove the prefix before showing that to the user. Also, it's not
exactly obvious that we can remove the prefix before passing that to
plugins/UI as we never know how those will be used further down the line...
The problem with just adding fields to each model is not so much a
problem from the point of view of 3rd party plugins accessing those
models that are modified in such a way, but rather with those resource
tables that are added by the third party plugins.
Completely agree.
These would have to be modified to add the product to their tables
too. Is the suggestion that we do that modification for externally
defined resources or only provide the ability for specific plugins?
The idea we are playing with is that in addition to translating 3rd
party plugin DMLs (SELECT/INSERT/UPDATE/DELETE) (to present plugins with
a view of trac/bh resources as seen from the current product scope), the
DDLs (CREATE/ALTER/DROP) for the custom tables should also be translated
to support product scope(s) - this would be accomplished by creating per
product custom table(s), prefixing the table name with product prefix.
This (in combination with the currently implemented SQL translation)
would present product unaware 3rd party plugins with product scoped
tables for both, trac/bh tables and any custom table the plugin would
create. References between the tables would also work and the content of
the tables would always represent data based on the resources in the
product scope.
Naive approach would be to solve 3rd party custom table the same way as
trac/bh tables (by adding product column). This does not work for two
reasons:
- schema upgrades - if the plugin chooses to upgrade it's custom table
schema the usual way of doing this is to copy data to temp table, drop
original table (this would effectively drop data for all products),
recreate new table with changed schema and fill it from temp table
- table schema changes - not really sure how to implement ALTER TABLE if
we modify the original schema (connected with the first reason)
To summarize the idea:
1. for 3rd party plugins that are product unaware, any custom table
being created is namespaced to the product by prefixing the table name
with the product name (in a similar way as discussed resource name
columns). SQL translator functionality will need to be extended to
support DDL.
2. the SQL translator will be changed in such a way that it will support
the following table 'types':
- non-translated tables - tables that need no translation (session,
cache, attachments,...)
- trac/bh tables with product scope - these are tables with product
specific resource (enum, component, ticket, milestone, version,...) -
the product scope for these tables is implemented using 'product' column
- 3rd party, product-unaware plugin custom tables - product scope
for these tables is implemented by prefixing the table name with product
prefix
3. changes to product unaware plugin install/upgrade process -
install/upgrade (IEnvironmentSetupParticipant) would need to be invoked
for all currently defined products (within that product scope of course)
4. adding a new product would need to invoke 3rd party (product unaware)
plugin installation
How does that sound to everyone?
Cheers,
Jure
