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Re: AW: [HACKERS] DROP TABLE inside a transaction block

From: Mike Mascari <mascarm(at)mascari(dot)com>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at>, "'pgsql-hackers(at)postgreSQL(dot)org'" <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: AW: [HACKERS] DROP TABLE inside a transaction block
Date: 2000-03-06 05:44:39
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Peter Eisentraut wrote:
> On Mon, 6 Mar 2000, Zeugswetter Andreas SB wrote:
> > Yes, that was also the general consensus on the list. No statement is
> > ever going to do an implicit commit of previous statements.
> I can understand that, but one of these days I hope we can offer the SQL
> semantics of transactions where you don't require a BEGIN. (*Optional*,
> people.) 

I often think that the current behavior with respect to BEGIN
often hurts PostgreSQL's reputation with respect to speed. If the
default behavior was to begin a transaction at the first
non-SELECT DML statement, PostgreSQL wouldn't fare so poorly in
tests of:

INSERT INTO testspeed(1);
INSERT INTO testspeed(2);
INSERT INTO testspeed(3);
INSERT INTO testspeed(100000);

where, the same .sql script submitted against other databases is
running in a transaction, and, as such, is not being committed
immediately to disk. Fortunately, the Ziff-Davis reviewer ran his
tests with fsync() off. But your run-of-the-mill enterprise
application developer is probably going to just install the
software via rpms and run their sql scripts against it.

> In that case you have to do *something* about non-rollbackable
> DDL (face it, there's always going to be one). Doing what Oracle does is
> certainly not the *worst* one could do. Again, optional.
> That still doesn't excuse the current behavior though.

I can certainly understand Andreas' viewpoint. If no DDL,
however, was allowed inside a transaction -or- you could
optionally turn on implicit commit, imagine how much easier life
INDEX, etc, not having to worry about restoring filesystem files,
or deleting them in aborted CREATE TABLE/CREATE INDEX statements,
etc. A far-reaching idea would be to make use of foreign keys in
the system catalogue, with triggers used to add/rename/remove
relation files. That could be done if DDL statements could not be
executed in transactions. With AccessExclusive locks on the
appropriate relations, a host of race-condition related bugs
would disappear. And the complexity involved with dropping (or
perhaps disallowing the dropping of) related objects, such as
triggers, indexes, etc. would be automatic.

Mike Mascari

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