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PostgreSQL 8.0 Released
Christopher Cashell writes "The PostgreSQL project has released version 8.0 of their well known Object-Relational Database. New features include: Win32 Native Server, Savepoints, Point-In-Time Recovery, Tablespaces, and lots more. Downloads are available via bittorrent for Unix/Linux, and the much anticipated Win32 version, or via ftp (use a mirror!)." (Here's the official announcement.)
Great, but why should I use PostgreSQL when I already have a database, you might ask? Here's why.
One of the most exciting features of 8.0 is plperl, their Perl-based server side language, allowing for triggers and persistent storage. On another note, I wish MySQL would catch up to PgSQL. Even if you don't like MySQL, the competition keeps them innovating. If PgSQL is light years ahead, what's pushing them?
Now all I need is a magical installer which will convert my existing 7.2.4 systems to 8.x without missing a single beat or disrupting the existing programs written against the old libs.... I'm serious!
Converting 200Gb of data is not something you want to try do without downtime.
All that said, it's good to see PostgreSQL always improving. Good one guys.
Hi Folks,
Please take it easy on 'wwwmaster'.
'www' fell over a couple of hours ago, and a couple of mirrors are coming online to round-robin the address.
Can someone please change the the first link ("PostgreSQL project") in the story to point to 'www'?
Thanks.
Goodbye Oracle, hello PostgreSQL. Now I can have a mostly SQL92 compliant database with ACID, transactions and now PITR and tablespaces that I can use on the server and on a win32 desktop.
For those of you wanting a great frontend, try PGAdmin3. It works on Win32 and Linux.
Not only that. Here's the most important link: What's New in 8.0. (To editors: why there are links to torrents, but no link to features?)
Sincerely,
Pan Tarhei Hosé, PhD.
"Homo sum et cogito ergo odi profanum vulgus et libido."
This is your sig. There are thousands more, but this one is yours.
PostgreSQL offers substantial additional power by incorporating the following additional concepts in such a way that users can easily extend the system:
Other features provide additional power and flexibility:
These features put PostgreSQL into the category of databases referred to as object-relational. Note that this is distinct from those referred to as object-oriented, which in general are not as well suited to supporting traditional relational database languages. So, although PostgreSQL has some object-oriented features, it is firmly in the relational database world.
It's got a long way to go as far as enterprise features.
There is no clustering support in PostgreSQL (and I mean real clustering, not some Java hack where transactions are shipped off to two separate DB servers, both of which don't know they're part of a cluster). This is pretty much a show stopper as far as using PostgreSQL in the company I work for, as high availability is a large concern, and any downtime would be serious.
In previous versions of PostgreSQL, the pg_dump and pg_restore tools were not very good - dumps that included tables or views often would fail on reimport because PostgreSQL wouldn't know the order in which to import everything. You also had to pass in a number of options on the command line just to get a dump that made sense, and large object support was kind of clunky.
That said, I still use PostgreSQL for many many projects and have used PostgreSQL for many years. It's a great product, but it isn't near Oracle in terms of enterprise level features.
$45 per U Colocation Special
LAPP, maybe, but certainly not WAPP.
Linux + Apache2 + PostgreSQL + Python == kickass webserver
I support the Center for Consumer Freedom
Master-Slave replication is available through Slony1. (This is currently used by Afilias on the .info domain) Slony2 is in progress and will provide multi-master replication.
Vacuuming is still necessary, but it no longer locks tables. The distribution includes a utility called pg_autovacuum which can take care of all the vacuuming tasks on an automated basis if you desire. (The gentoo release automatically installs this with a nice init script :) )
... and it would really really rock!
Said that, PostgreSQL is a really great thing, and being FOSS, I could of course always go ahead and add the named features... .)
I would consider the PostgreSQL gotchas to be of an entirely different category as the MySQL gotchas.
In PostgreSQL the gotchas are all about performance. And while it may be bad that the database crawls if I didn't schedule a job with vacuum and analyze, that does not have any long term effects. I just run the maintenance tasks manually, add them to a cronjob and I am good to go.
In MySQL however, the gotchas are mostly about data integrity. And that means that they can be disasterous because they can lead to dataloss. Unless you can explain to me how to get back whatever was silently truncated by MySQL if I discover the problems a few days later.
I do very much prefer PostgreSQLs focus on data integrity. But of course I actually read the manual so I won't be bitten by them in either database.
Check out the new Slony replication engine:
http://www.slony.info/
It is probably the best master->slave data replication engine for PostgreSQL at the moment. It is free and developed by one of the core developers.
In my last project I was forced to use MySQL due to hosting issues. I still believe that MySQL is the Access of the OSS dtabases (in a non-GUI way).
The dirty secret is that Postgres is actually easier to install and administer than mysql. I don't want to get into a religious argument with mysql users but ... oh hell yes I do.
I have worked with self-educated programmers who did not know how to do simple table joins or even modestly complex SQL queries or transactions, because they had learned what they thought was SQL by using Mysql. There is a whole generation of developers who now think that transactions aren't really necessary in a database application.
Postgres is really an Oracle killer at this point, and I know, having used Oracle. There is quite simply no reason to use any other relational database at this point, especially to back a live web site.
I have several tables with over 3 million rows, and most aggregates return immediately (or nearly immediately). count(*) is the only dog since it reads every row to get the count, but it's acceptable since I rarely count all rows in the table. I've often wondered why the developers couldn't keep an internal count of all active rows, so count(*) would return immediately, but I'm sure they have their reasons.
You've got to be joking about PostgreSQL having a weak optimizer. If it's weak, only the computer can tell.
Your Wiki link spent most of its space praising PostgreSQL for its advanced features, while your intent is clearly to denigrate it. If that represents PosgreSQL's worst facets, then I am very, very happy.
7.x compiles right out of the box- in fact, Apple's Remote Desktop system actually installs and uses PostgreSQL for all its data storage (client system data and whatnot; ARD can collect a lot of per-system data). Very slick.
Please help metamoderate.
In MySQL (with MyISAM tables), the reason things like count(*) are fast is that MyISAM pre-computes those values. It can do this because it locks the table on insert and update. PostgreSQL doesn't lock the table on modifications -- it allows concurrent access via Multi-Version Concurrency Control (MVCC). Basically, each row in the DB has additional information (used internally by PostgreSQL), which stores which transaction created and last modified the row. PG uses this to determine if any given row should be "visible" to the current transaction. Because this informaiton is constantly changing (and varies from transaction to transaction), you can't precompute things like count(*) and sum(*). See http://developer.postgresql.org/pdf/internalpics.p df for more info (start around page 56).
Postgresql is ready to take on the smaller, non-critical databases that oracle used to get. This is significant proportion of the databases out there, and will take revenue away from oracle. (Mysql will actually probably take more revenue away, but it has too many quality problems and functionality gaps to really deserve to.)
But there are many other, more demanding databases that postgresql isn't yet ready for. Oracle, DB2, and even SQL Server 2005 all have very mature & solid: optimizers, replication, partitioning solutions, parallelism, failover/clustering support, etc.
Here are two examples:
Using db2 for example, you can create a view which is automatically populated by the database like a table (MQT). Then any queries against the base tables that could be sped up by hitting this view will be rewritten by the engine to hit the view. Now, this might seem like needless fluff if you're just writing a hobby php app. But if you need to implement a commercial app like SAP with its 6,000 tables - and you have performance issues - you can make adjustments in the database layer this way. Also, if you're provoding adhoc reporting for hundreds of users on a terrabyte of data - this technique can provide *dramatic* performance benefits.
Another example is partitioning. Back to db2 (which I work with the most): you can spread a database across a dozen separate servers using a hashkey. Now, every query will have all dozen servers working independently on its own fraction of the data. On each of those servers, you can then partition again, this time using ranges or values (MDC) - so that data that doesn't apply to a query will be skipped in tablescans of that table. Using these techniques you can get sub-second response to *adhoc* queries against a terrabyte of data - without indexes (notoriously unreliable here).
Lots more examples where the above came from. Sure, you will pay real money for licensing, hardware, and labor to implement these. Then again, the two above features actually save you in hardware costs. Additionally, some problems are big enough that they can easily justify the cost of licensing a product like this. I've seen these techniques used to save companies million, even hundreds of millions of dollars.
Postgres knows how many rows are in the table, but it does not know how many of those you can see. Some of them may be inserted speculatively by another transaction. Postgres needs to go through each row to determine whether or not that row is actually visible to you. It is possible to turn this into an O(1) operation if you're willing to do sufficient work on inserts and deletes. Whether this is a good tradeoff depends on how often you do count(*) compared to how often you do inserts and deletes.
Finally! A year of moderation! Ready for 2019?
Oracle will always have more features than any other given database product you care to compare it to, and there will always be those who find some of those Oracle-unique features irresistable. That's what it means to be the central product of a very large, wealthy and reasonably effective software company.
It is not a very meaningful comparison, though. Oracle also has a lot of stuff that nobody would be happy to see tacked on to PostgreSQL. Oracle is notoriously difficult to administer. The download of Oracle's database product is probably 500 times larger than PostgreSQL. (and 20 times larger than Oracle itself was just a few versions ago, which is interesting, and yes I'm guesstimating but still...)
In short, PostgreSQL doesn't need all the features of the Oracle db to be successful, as *nix and NT did not need all the features of a mainframe OS to be successful.
Now before I get modded down, I be to remind whoever might read this that what I am saying is FACT. - bogaboga
Try Slony for full, production quality replication on PostgreSQL:
http://www.slony.info/
Performance is still an issue when you don't read the manual and never perform maintenance on your database. No matter how good the planner is, if it doesn't have acurate statistics because nobody ever runs ANAYZE your database will crawl. No matter which version you use, if you never VACUUM dead row versions will accumulate and eventually kill your performance.
I use PostgreSQL on a daily basis and when I change a database schema I will make sure that I run a VACUUM ANALYZE after committing the changes. But many of the people that we host don't bother to read the manual and don't do this. Usually this is no big deal because it gets picked up by the scheduled jobs. But every now and then somebody calls in a panic because their website is slow. And it always turns out to be major schema changes throwing the planner off. A quick VACUUM ANALYZE gets the performance up again and the customer is happy and has (hopefully) learned a valuable lesson.
This is a real gotcha in PostgreSQL. It has made a few of our customers' websites crawl for a few hours on occasion. But it has never caused dataloss.
While I think that PostgreSQL is the best open source database out there, there is one very important gotcha wrt: MVCC which can cause data integrity. This only happens when autovacuum is not running, of course.
If you run enough transactions between vacuum runs (iirc a billion), the transaction counter will wrap around and suddenly your data does not have a consistant point of reference regarding visible transactions. Now, if you wait for a billion transactions to run VACUUM, you either:
1) Have extremely poor performance anyway (not to mention having all your stats off so the planner is doing seq scans when it should use an index)
2) Are doing something with the database which I cannot imagine (I guess a huge number of select statements could cause this, but updates cause old tuples to sit around, so you would have bad performance).
Now, I am not aware of this ever actually having happened, but it is in the documentation, so I figure I should point it out. Of course if you let the database get to this point, then you have bigger problems than your data (chief among them being the IT staff and/or management)..
In general, PostgreSQL focuses on data integrity to a degree not seen elsewhere in the open source database world. Even Firebird does not have such a heavy focus in this area, though to be fair it is a different enough product that their focus works well in their target markets.
My company offers application development, remote administration, and implimentation services for PostgreSQL, MySQL, and Firebird. I am very excited about this release because it will enable us to do more with the database manager which makes us most productive.
As a side note, PostgreSQL-Win32 will not run on Win9x because it requires an NTFS filesystem, iirc. So it is not a perfect solution for Windows development yet (until Win9x fades into the distance or until they decide that they should port it to FAT). Of course you could still use the Cygwin installation, I think. But it is better, IMO, to run it on a arguably stable system anyway.
LedgerSMB: Open source Accounting/ERP
Before, to do this, you had to create a temporary table with the changed column type, copy all the data over to it, and then rename the temp table as the old table.
Thank you Postgres team! Now, if we can rename a column, that would be a nice bonus.
You're telling me that MySQL locks the entire table when I insert a row? You must be joking - that would bring a database to it's knees.
I'm an Oracle guy, and this is how they do it:
Oracle has the best technology in the industry, hands down (DB2 didn't even get triggers until v5). Postgres appears to be paying much more attention to Oracle's methods than MySQL.
Guess which database I'd use if I had no money to spend?
Oxford University announced a while back that they will be scrapping most of their proprietary DBs for PostgreSQL over the course of '05:
http://news.zdnet.co.uk/software/applications/0