t8 can accomodate 64 flags - the space saving can be
substantial.
Thanks,
-Slava.
- Original Message -
From: "Scott Marlowe"
To: "Slava Moudry"
Cc: "Robert Haas" ;
Sent: Thursday, August 20, 2009 6:58 PM
Subject: Re: [PERFORM] number of rows estimation
Robert Haas escribió:
> Scott, did you check whether a toast table got created here and what
> the size of it was?
A table with only bool columns (and, say, one int8 column) would not
have a toast table. Only varlena columns produce toast tables.
--
Alvaro Herrera
On Thu, Aug 20, 2009 at 9:58 PM, Scott Marlowe wrote:
> On Thu, Aug 20, 2009 at 7:32 PM, Scott Marlowe wrote:
>> 2009/8/20 Slava Moudry :
>>> Hi,
>>> Yes, I thought about putting the bit-flags in separate fields.
>>> Unfortunately - I expect to have quite a lot of these and space is an issue
>>> w
0:55 AM
To: Scott Marlowe
Cc: Slava Moudry; pgsql-performance@postgresql.org
Subject: Re: [PERFORM] number of rows estimation for bit-AND operation
On Tue, Aug 18, 2009 at 6:34 PM, Scott Marlowe wrote:
> 2009/8/18 Slava Moudry :
>>> increase default stats target, analyze, try again.
>&g
On Thu, Aug 20, 2009 at 7:32 PM, Scott Marlowe wrote:
> 2009/8/20 Slava Moudry :
>> Hi,
>> Yes, I thought about putting the bit-flags in separate fields.
>> Unfortunately - I expect to have quite a lot of these and space is an issue
>> when you are dealing with billions of records in fact table, s
2009/8/20 Slava Moudry :
> Hi,
> Yes, I thought about putting the bit-flags in separate fields.
> Unfortunately - I expect to have quite a lot of these and space is an issue
> when you are dealing with billions of records in fact table, so I prefer to
> pack them into one int8.
For giggles I cre
On Tue, Aug 18, 2009 at 6:34 PM, Scott Marlowe wrote:
> 2009/8/18 Slava Moudry :
>>> increase default stats target, analyze, try again.
>> This field has only 5 values. I had put values/frequencies in my first post.
>
> Sorry, kinda missed that. Anyway, there's no way for pg to know which
> operat
essage-
From: Scott Marlowe [mailto:scott.marl...@gmail.com]
Sent: Tuesday, August 18, 2009 2:58 PM
To: Slava Moudry
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] number of rows estimation for bit-AND operation
2009/8/18 Slava Moudry :
> Hi Scott,
> Thank you for reply.
>
Original Message-
From: Scott Marlowe [mailto:scott.marl...@gmail.com]
Sent: Tuesday, August 18, 2009 12:09 AM
To: Slava Moudry
Cc: pgsql-performance@postgresql.org
Subject: Re: [PERFORM] number of rows estimation for bit-AND operation
On Mon, Aug 17, 2009 at 2:07 PM, Slava Moudry wrote:
> Hi,
>
&g
2009/8/18 Slava Moudry :
>> increase default stats target, analyze, try again.
> This field has only 5 values. I had put values/frequencies in my first post.
Sorry, kinda missed that. Anyway, there's no way for pg to know which
operation is gonna match. Without an index on it. So my guess is
th
2009/8/18 Slava Moudry :
> Hi Scott,
> Thank you for reply.
> I am using Postgres 8.4.0 (btw - great release --very happy about it) and I
> got a different plan after following your advice:
Yeah, you're returning most of the rows, so a seq scan makes sense.
Try indexing / matching on something mo
On Mon, Aug 17, 2009 at 2:07 PM, Slava Moudry wrote:
> Hi,
>
> I am using int8 field to pack a number of error flags. This is very common
> technique for large tables to pack multiple flags in one integer field.
>
> For most records – the mt_flags field is 0. Here is the statistics (taken
> from pg
Hi,
I am using int8 field to pack a number of error flags. This is very common
technique for large tables to pack multiple flags in one integer field.
For most records - the mt_flags field is 0. Here is the statistics (taken from
pgAdmin Statistics tab for mt_flags column):
Most common Values: {
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