Java Generate Id Thats Unique From Postgresql Primary Key

Posted on  by

Edit generated media key not working in vegas 12. Nov 01, 2012  sony vegas Pro 12 unable to edit generated media - Creative COW's VEGAS Pro user support and discussion forum is a great resource for Vegas users wishing to learn more about Vegas without all the noise. Oct 07, 2012  This is a very common problem among sony vegas users, It is a new problem fix without upsiding and downshifting taskbars. If it works so please like and subscribe. Comment for any doubt.

Good day, I'm asking myself if there is a performance issue in using an integer of varchar(24) PRIMARY KEY in a product table. I've read that there is no speed issue in the query, but that the only. PRIMARY KEY constraint. The PostgreSQL PRIMARY KEY is a column in a table which must contain a unique value which can be used to identify each and every row of a table uniquely. So it can be said that the PRIMARY KEY of a table is a combination of NOT NULL and UNIQUE constraint. Good day, I'm asking myself if there is a performance issue in using an integer of varchar(24) PRIMARY KEY in a product table. I've read that there is no speed issue in the query, but that the only. For a relational database like PostgreSQL, it could widely be considered a sin among developers not to include a primary key in every table. It is therefore crucial that you do your utmost to add that all-important primary key column to every table, and thankfully Postgres provides two methods for accomplishing this task. SERIAL data type allows you to automatically generate unique integer numbers (IDs, identity, auto-increment, sequence) for a column. Quick Example: - Define a table with SERIAL column (id starts at 1) CREATE TABLE teams ( id SERIAL UNIQUE, name VARCHAR(90) ); - Insert a row, ID will be automatically generated INSERT INTO teams (name) VALUES ('Tottenham Hotspur'); - Retrieve generated ID.

PostgreSQL: Unique Constraints This PostgreSQL tutorial explains how to create, add, and drop unique constraints in PostgreSQL with syntax and examples. What is a unique constraint in PostgreSQL? A unique constraint is a single field or combination of fields that uniquely defines a record. interfaces into PostgreSQL, PHP and C (classes wrapping the C structures and functions). (id UUID DEFAULT 'uuid(4)' PRIMARY KEY); (For my application, as it happens, I don't need to generate UUIDs in the database, but I recognize that would be useful.) Actually, serverside generation of uuids is the least interesting.

I have a table that I am using to store email token data for DSPAM.

Java Generate Id Thats Unique From Postgresql Primary Key

I'm noticing that a handful (4-16) of rows with duplicate columns
(uid,token) are sneaking into the table every day despite the
primary key constraint.

The server currently processes a few thousand emails per day, and
this particular table currently has about 4.5 million rows in it.

I feel as though I must be missing something here, because I have
always strongly assumed that postgresql prevents this sort of chaos
from happening by default.

When these duplicate pairs make their way into the table, all havoc
breaks loose ;) The rows with the duplicate pairs seem to become
land mines. The postgresql process handling a query that
subsequently runs across one of these rows dies, taking down
the DSPAM daemon with it, and sometimes corrupting the postgresql
shared memory enough that the postmaster has to shutdown the other
processes and restart everything anew [1].

I am usually able to clean things up by running the following, but
once or twice I've had to drop the unique constraint before
postgresql would process the request without choking:

delete from dspam_token_data
where row(uid,token) in
(select uid,token
from dspam_token_data
group by uid,token
having count(*) > 1);

(I don't worry about preserving one of the duplicates here.)

I'm running postgresql-8.1.3. Here is the table in question:

CREATE TABLE dspam.dspam_token_data
(
uid int4 NOT NULL,
token int8 NOT NULL,
spam_hits int4,
innocent_hits int4,
last_hit date,
CONSTRAINT dspam_token_data_pkey PRIMARY KEY (uid, token)
)
WITHOUT OIDS;

[2]

Java Generate Id That's Unique From Postgresql Primary Key Index

What steps can I take to fix this? Is there any additional
information I can provide?

I've cleaned the table many times now. I then run VACUUM ANALYZE.

My next step will probably be to hack the DSPAM sources to make the
application more careful about not trying to insert rows that would
violate the unique constraint. Even still, it seems that would only
reduce the frequency of these occurrences, not eliminate them
completely.

Thanks!

Java Generate Id That's Unique From Postgresql Primary Key Examples

Cheers,

-- Travis

Java Generate Id That's Unique From Postgresql Primary Key Of Life

----
Notes:
[1] A condensed log file showing off exactly what happens here is
attached.

[2] Previously, the table lacked a primary key and instead used a
unique constraint and index. This yielded the exact same results I
am currently seeing using a two-column primary key, as above. The
old table schema was:

CREATE TABLE dspam.dspam_token_data
(
uid int4,
token int8,
spam_hits int4,
innocent_hits int4,
last_hit date,
CONSTRAINT dspam_token_data_uid_key UNIQUE (uid, token)
)
WITHOUT OIDS;

Java Generate Id That's Unique From Postgresql Primary Key Tutorial

Thanks for the answer,

I am unable to use ossp_uuid due to package install and/or server
rebuild requirement.

So I am trying to roll my own, and
digest(quote_literal(random()+random()), 'sha256'), 'hex') doesn't
work:

I have created this table and inserted 200000 rows (two million).
This is more or less now my application looks now. It uses bigserial.
And I need to add some unique hash:
CREATE TABLE item
(
item_id bigserial NOT NULL,
title character varying,
CONSTRAINT pk PRIMARY KEY (item_id)
)
WITH (
OIDS=FALSE
);

Now I add the hash column:
ALTER TABLE item ADD COLUMN hash1 character varying NOT NULL DEFAULT
encode(digest(quote_literal(random()+random()), 'sha256'), 'hex');
ALTER TABLE item ADD UNIQUE (hash1);

When I executed this two statements, ALTER TABLE ADD COUMN, ADD
UNIQUE, after 20 seconds I got this message:
NOTICE: ALTER TABLE / ADD UNIQUE will create implicit index
'item_hash1_key' for table 'item'
ERROR: could not create unique index 'item_hash1_key'
DETAIL: Table contains duplicated values.
********* Error **********
ERROR: could not create unique index 'item_hash1_key'
SQL state: 23505
Detail: Table contains duplicated values.

So this means random()+random() is not random even within 2,000,000 iterations!

Java Generate Id That's Unique From Postgresql Primary Key Mean

If you suggest accessing /dev/urandom directly- I cannot do that
because my application runs on mac,windows and linux. It would be
maintenance nightmare.

Any suggestions?

Java Generate Id Thats Unique From Postgresql Primary Keys

Thanks.

On Fri, Jan 29, 2010 at 10:20 PM, Adrian von Bidder
<avbidder(at)fortytwo(dot)ch> wrote:
> On Friday 29 January 2010 11.21:00 Joe Kramer wrote:
>> We have bunch of servers running the app and rebuilding postgres with
>> support for ossp_uuid on all servers is time consuming.
>> Is there a way of doing it without third party dependency like
>> ossp_uuid? Should I just run md5(random number), will itbe the same ?
>
> If you're building your own: at least use sha1 instead of md5.
>
> (Even md5 *should* be safe in the absence of malicious attacks, but md5 is
> generally not recommended anymore.)
>
> Everything depends on the quality of your random numbers. I don't know how
> much randomness pg's random() delivers, and as I've said I haven't looked
> what the uuid module does.
>
> (To give you an example: if random() only delivers a random 32 bit float
> value, the 160 bits of SHA-1 will not be used. You'll only use 4 billion
> different values and you *will* soon get collisions.)
>
> If I were to roll my own, I'd just use 256 bit of /dev/random (or, depending
> on the application, possibly /dev/urandom and take the risk that my values
> aren't that random.) Since it's random anyway, there's no need to use a
> hash. (Not sure: can a SQL function read arbitrary binary files or will a C
> module be necessary?)
>
> Speed: just did a quick test on one machine. reading 1kB from /dev/random
> takes about 1s. (constant 5MB/s disk activity with lots of seeking going
> on, no hw random device.) So you'd get ca. 32 id values per second. Don't
> know if that's a lot or not for your application.
>
> Magnus: can you elaborate on uuid not being secure? AFAICT v4 uuid are
> supposed to be essentially a random number formatted in a certain way.
>
> cheers
> -- vbi
>
>
> --
> featured product: GNU Privacy Guard - http://gnupg.org
>