:03 AM
To: Brandon Aiken
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] Difference between UNIQUE constraint vs index
"Brandon Aiken" <[EMAIL PROTECTED]> writes:
> SQLite, MySQL, and MS Access each use indexes for unique constraints.
> Doesn't the SQL spec speci
Informix:
http://publib.boulder.ibm.com/infocenter/idshelp/v10/index.jsp?topic=/com.ibm.sqls.doc/sqls285.htm
AFAICS, Oracle as well.
John
On 2/28/07, Tom Lane <[EMAIL PROTECTED]> wrote:
"Jim C. Nasby" <[EMAIL PROTECTED]> writes:
> In some databases if you know that an index just happens to be
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On 02/28/07 10:31, Joshua D. Drake wrote:
I would imagine that other DBMSes also enforce uniqueness by means of
indexes, because it'd be awful darn expensive to enforce the constraint
without one; but I'm only guessing here, not having l
>>> I would imagine that other DBMSes also enforce uniqueness by means of
>>> indexes, because it'd be awful darn expensive to enforce the constraint
>>> without one; but I'm only guessing here, not having looked. Can anyone
>>> point to a real system that enforces unique constraints without an
>
"Brandon Aiken" <[EMAIL PROTECTED]> writes:
> SQLite, MySQL, and MS Access each use indexes for unique constraints.
> Doesn't the SQL spec specify that CREATE INDEX can be used to create
> UNIQUE indexes?
No, there is no such command in the SQL spec. In fact the concept of an
index does not appea
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On 02/28/07 00:16, Tom Lane wrote:
> "Jim C. Nasby" <[EMAIL PROTECTED]> writes:
>> In some databases if you know that an index just happens to be unique
>> you might gain some query performance by defining the index as unique,
>> but I don't think the
EMAIL PROTECTED] On Behalf Of Tom Lane
Sent: Wednesday, February 28, 2007 1:17 AM
To: Jim C. Nasby
Cc: John Jawed; pgsql-general@postgresql.org
Subject: Re: [GENERAL] Difference between UNIQUE constraint vs index
"Jim C. Nasby" <[EMAIL PROTECTED]> writes:
> In some databa
"Jim C. Nasby" <[EMAIL PROTECTED]> writes:
> In some databases if you know that an index just happens to be unique
> you might gain some query performance by defining the index as unique,
> but I don't think the PostgreSQL planner is that smart.
Actually, the planner only pays attention to whether
Adding -general back in.
On Tue, Feb 27, 2007 at 07:19:15PM -0600, John Jawed wrote:
> This is more or less correct, I was looking for performance gains on
> the [possible] differences during DML and DDL.
>
> If Jim is correct, is there a particular reason that PostgreSQL does
> not behave like o
This is more or less correct, I was looking for performance gains on
the [possible] differences during DML and DDL.
If Jim is correct, is there a particular reason that PostgreSQL does
not behave like other RDBMs without a SET ALL DEFERRED? Or is this a
discussion best left for -HACKERS?
On 2/27
John Jawed wrote:
> Is there any difference as far as when the "uniqueness" of values is
> checked in DML between a unique index vs a unique constraint? Or is
> the only difference syntax between unique indices and constraints in
> PostgreSQL?
They are functionally the same and unique constraint w
On Tue, Feb 27, 2007 at 06:43:51PM -0600, John Jawed wrote:
> Is there any difference as far as when the "uniqueness" of values is
> checked in DML between a unique index vs a unique constraint? Or is
> the only difference syntax between unique indices and constraints in
> PostgreSQL?
Syntax only,
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