[Engine-devel] Move SQL out of stored procedures

Mon Apr 1 21:35:03 UTC 2013

----- Original Message -----
> From: "Laszlo Hornyak" <lhornyak at redhat.com>
> To: "Libor Spevak" <lspevak at redhat.com>
> Cc: "Juan Hernandez" <jhernand at redhat.com>, engine-devel at ovirt.org
> Sent: Thursday, March 28, 2013 5:31:34 PM
> Subject: Re: [Engine-devel] Move SQL out of stored procedures
> 
> 
> 
> ----- Original Message -----
> > From: "Libor Spevak" <lspevak at redhat.com>
> > To: "Itamar Heim" <iheim at redhat.com>
> > Cc: "Juan Hernandez" <jhernand at redhat.com>, engine-devel at ovirt.org
> > Sent: Thursday, March 28, 2013 4:04:20 PM
> > Subject: Re: [Engine-devel] Move SQL out of stored procedures
> > 
> > Hi,
> > 
> > apart from SQL vs. stored procedures discussion, I am trying to
> > understand what we can get if we support more databases...

Sorry for joining this discussion so late (I was in a vacation)
anyway
two points missing from SQL VS. SP are 
1) security - With plain SQL we will have to handle SQL Injection
2) It is more economic to pass a call to SP than the full SQL on the wire... 

> > 
> > Some points:
> > 1. Is there a real need by end-users/customers to run it on e.g.
> > Oracle
> > only? (performance, stability, easier administration).
> 
> Usually companies have one database and they are trying to stick to that one.
> Having two doubles the resource needs, you need one more DBA team, care for
> mirrors, backups. So it almost doubles the costs.

Generally, I agree with Alon B L , if you have to support X DBs you are not doubling the effort by X
Actually, we had already experience with that when we supported both MS SQL & Postgres
I believe that as we have some customers with large installations, performance counts and the best way (and sometimes teh only way) id the DB layer 

> This is why I frequently hear people asking if we plan to support XyDB in the
> future. PostgreSQL is cool, but those who already use MySQL/MariaDB, they
> just do not want one more.
> 
> > What is the future of PostgreSQL?
> > 
> > 2. Is it decided by architectural board, what kind of databases we
> > would
> > like to support? (cannot support any db)
> 
> With a JPA we could support most mainstream relational databases, but in my
> opinion 99 percent of people run oracle, mysql/mariadb or postgresql. So
> maybe we do not have to think in big number of database engines.
> This is theoretical since JPA is still on wishlist :(
> 
> > 
> > 3. Are we talking about the Engine only, or there will be a need to
> > rewrite ETL mappings and upgrade DWH database, or maybe modify
> > JasperReports templates (simply, some DB types behave differently)?
> > Maybe we can look at JasperSoft solution, they support more
> > databases.

IMHO , ETL & DWH are perfect candidates for NO SQL which is already supported by Jasper

> > 
> > 4. Current full/incremental upgrade process of PostgreSQL is IMHO
> > very
> > good tuned (it is similar to dbmaintain.org tool - Java
> > implementation -
> > I used successfully on one project - after some changes of course). I
> > do
> > not believe we can use or easily develop general upgrade/migration
> > tool,
> > and XML based (I am sorry Alissa, not sure about Liquibase, I haven't
> > studied it deeply, but there is a need to incrementally change db
> > objects, but sometimes also to migrate data to new structures, the
> > most
> > flexible and quickest is to do it using native SQL, but yes, it
> > depends
> > on the project needs...).

I had evaluated Liquibase and I think that managing your DB upgrades via XML is very unfriendly and very limited as you reach complex upgrades as we had in the past.
Just think of the tables in which we change the key from long to UUID , there is no way to do that in such tools

> > 
> > 5. As a developer, with every new column I need to write upgrade
> > scripts, prepare test environments and test all scenarios several
> > times
> > on different databases, so time-consuming.

Did it also , again , since our SQL is 90% simple , the effort of writing a SP for more than one DB is not so high (and you have free converters you can use for that)

Finally, embedded SQL in the Java code is not a good idea, it will be hard to maintain it and it is not advancing us in supporting more than one database.
We have already SQL generated in the Java code on the search engine and IMHO this is one of the parts in the applications that needs a rewrite ...

> > 
> > 
> > On 27.3.2013 13:53, Itamar Heim wrote:
> > > On 03/26/2013 08:39 PM, Alon Bar-Lev wrote:
> > >>
> > >>
> > >> ----- Original Message -----
> > >>> From: "Juan Hernandez" <jhernand at redhat.com>
> > >>> To: engine-devel at ovirt.org
> > >>> Sent: Tuesday, March 26, 2013 7:34:04 PM
> > >>> Subject: [Engine-devel] Move SQL out of stored procedures
> > >>>
> > >>> Hello,
> > >>>
> > >>> I would like to start a discussion about the subject. I think
> > >>> this is
> > >>> something we need to do if one day we want to be able to use any
> > >>> database other than PostgreSQL.
> > >>
> > >> Hello,
> > >>
> > >> I think that database layer is a software interface like any other
> > >> software interface, if done properly, a dba can convert the stored
> > >> procedure to any other database without any code change.
> > >>
> > >> This way the database specific implementation lives within the
> > >> database and maintained by the designated dba.
> > >>
> > >> Fixups and optimizations can be done in database without touching
> > >> the
> > >> code.
> > >>
> > >> Backward compatibility layer is much simpler to implement based on
> > >> stored procedures than complex set of views and tables.
> > >>
> > >> Also, accessing the database via different technologies is simpler
> > >> if
> > >> there is maintained database interface (stored procedures).
> > >>
> > >> I've seen hibernate based java applications that promised to be
> > >> database independent but at the edges when performance counts, the
> > >> DAO became HQL, then a special dialect and finally database
> > >> specific
> > >> SQLS.
> > >
> > > there may be db specific optimization/logic, but I don't see why we
> > > need STPs for 80% (if not more) of the CRUD and basic queries.
> > >
> > > I also agree with Tal later in the thread that its a good question
> > > if
> > > we can't find a better solution than re-writing the sql's in the
> > > code
> > >
> > > _______________________________________________
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> > > Engine-devel at ovirt.org
> > > http://lists.ovirt.org/mailman/listinfo/engine-devel
> > 
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