Re: Re: Using Random Sequence as Key

Bernardo,

> I needed the random field because if I use serial and the user gets a
> 34203
> he's sure that 34202 exists, and that (probably, there where 34202
> inserts
> before him (or at least an offset + some)). Using a random just makes
> the
> user totally blind.
> As I said I could use a serial for indexing the table but I NEED the
> random
> field and I need to to be unique since all the queries will be using
> it as a
> search parameter.
> If inserting this way is slow it's not such a big deal since it's a
> small db
> and inserts are seldom made.
> Thanks in advance for any help.

Here's another suggestion for you then:

1. Add a sequence "Sales_sq"

1. write a custom function for new id numbers:
CREATE FUNCTION new_sales_id() RETURNS INT4 AS '
DECLARE
timeportion VARCHAR;
serialportion INT4;
BEGIN
timeportion := to_char(current_timestamp, ''ms'');
-- (or whatever the abbreviation for 2-digit milliseconds is)
serialportion := 100*(nextval(''sales_seq''));
RETURN CAST(to_number(timeportion) AS INT4) + serialportion;
END;

3. Then set the id column to default to this new function.

This would give you (after you correct my mistakes) a number, the first
X digits of are Serial, and the last 2 digits based on the server's
internal clock. Thus, the numbers would *not* be sequential, and would
appear fairly random, but would be unique *without* and expensive check
for that value anywhere in the table for each insert.

-Josh Berkus

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