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* Incorrect mention of number of columns?
@ 2023-11-03 16:09 Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
0 siblings, 2 replies; 7+ messages in thread
From: Daniel Westermann (DWE) @ 2023-11-03 16:09 UTC (permalink / raw)
To: pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org>
Hi,
from the limits page in the docs: https://www.postgresql.org/docs/current/limits.html
"...but a tuple of 1600 bigint columns would consume 12800 bytes and would therefore not fit inside a heap page".
Creating a table with 1600 bigint columns does work with a 8k blocksize:
$ cat gen_tab.sh
#!/bin/bash
AMOUNT_OF_COLS=$1
DATA_TYPE=$2
STATEMENT="create table t ( "
for (( i=1 ; i<${AMOUNT_OF_COLS} ; i++ ));
do
STATEMENT+=" col${i} ${DATA_TYPE},"
done
STATEMENT+="col${AMOUNT_OF_COLS} ${DATA_TYPE} );"
echo ${STATEMENT}
.$ /gen_tab.sh 1600 bigint > a.sql
$ psql -f a.sql
CREATE TABLE
$ psql -c "\d t"
...
col1598 | bigint | | |
col1599 | bigint | | |
col1600 | bigint | | |
Am I missing something?
Regards
Daniel
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Incorrect mention of number of columns?
@ 2023-11-03 16:12 Magnus Hagander <magnus@hagander.net>
parent: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
1 sibling, 0 replies; 7+ messages in thread
From: Magnus Hagander @ 2023-11-03 16:12 UTC (permalink / raw)
To: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>; +Cc: pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org>
On Fri, Nov 3, 2023 at 5:09 PM Daniel Westermann (DWE)
<daniel.westermann@dbi-services.com> wrote:
>
> Hi,
>
> from the limits page in the docs: https://www.postgresql.org/docs/current/limits.html
>
> "...but a tuple of 1600 bigint columns would consume 12800 bytes and would therefore not fit inside a heap page".
>
> Creating a table with 1600 bigint columns does work with a 8k blocksize:
>
> $ cat gen_tab.sh
> #!/bin/bash
> AMOUNT_OF_COLS=$1
> DATA_TYPE=$2
> STATEMENT="create table t ( "
> for (( i=1 ; i<${AMOUNT_OF_COLS} ; i++ ));
> do
> STATEMENT+=" col${i} ${DATA_TYPE},"
> done
> STATEMENT+="col${AMOUNT_OF_COLS} ${DATA_TYPE} );"
> echo ${STATEMENT}
>
> .$ /gen_tab.sh 1600 bigint > a.sql
>
> $ psql -f a.sql
> CREATE TABLE
>
> $ psql -c "\d t"
> ...
> col1598 | bigint | | |
> col1599 | bigint | | |
> col1600 | bigint | | |
>
> Am I missing something?
It will fail when you try to insert data in it.
//Magnus
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Incorrect mention of number of columns?
@ 2023-11-03 16:12 Tom Lane <tgl@sss.pgh.pa.us>
parent: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
1 sibling, 1 reply; 7+ messages in thread
From: Tom Lane @ 2023-11-03 16:12 UTC (permalink / raw)
To: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>; +Cc: pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org>
"Daniel Westermann (DWE)" <daniel.westermann@dbi-services.com> writes:
> Creating a table with 1600 bigint columns does work with a 8k blocksize:
Yeah, but populating it would not (unless many of the columns were
NULL).
regards, tom lane
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Incorrect mention of number of columns?
@ 2023-11-03 16:18 Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
parent: Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 7+ messages in thread
From: Daniel Westermann (DWE) @ 2023-11-03 16:18 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org>
>"Daniel Westermann (DWE)" <daniel.westermann@dbi-services.com> writes:
>> Creating a table with 1600 bigint columns does work with a 8k blocksize:
>Yeah, but populating it would not (unless many of the columns were
>NULL).
Ok, but then should the documentation be more precise? It seems a bit odd to let users create such a table without at least a warning.
Regards
Daniel
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Incorrect mention of number of columns?
@ 2023-11-03 16:42 Tom Lane <tgl@sss.pgh.pa.us>
parent: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
0 siblings, 1 reply; 7+ messages in thread
From: Tom Lane @ 2023-11-03 16:42 UTC (permalink / raw)
To: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>; +Cc: pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org>
"Daniel Westermann (DWE)" <daniel.westermann@dbi-services.com> writes:
>> Yeah, but populating it would not (unless many of the columns were
>> NULL).
> Ok, but then should the documentation be more precise? It seems a bit odd to let users create such a table without at least a warning.
Given the impact of NULLs, and the fact that usually tables have some
variable-width columns, I doubt that a creation-time warning could be
accurate enough to be useful.
regards, tom lane
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Incorrect mention of number of columns?
@ 2023-11-03 17:04 Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
parent: Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 7+ messages in thread
From: Daniel Westermann (DWE) @ 2023-11-03 17:04 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org>
>"Daniel Westermann (DWE)" <daniel.westermann@dbi-services.com> writes:
>>> Yeah, but populating it would not (unless many of the columns were
>>> NULL).
>> Ok, but then should the documentation be more precise? It seems a bit odd to let users create such a table without at least a warning.
>Given the impact of NULLs, and the fact that usually tables have some
>variable-width columns, I doubt that a creation-time warning could be
>accurate enough to be useful.
I am not speaking about a warning at creation time, but rather a warning in the docs. Something like: Although a table with e.g. 1600 bigint columns can be created, creating a tuple of more than 8160 bytes will fail.
Regards
Daniel
^ permalink raw reply [nested|flat] 7+ messages in thread
* Re: Incorrect mention of number of columns?
@ 2023-11-03 17:08 Bruce Momjian <bruce@momjian.us>
parent: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
0 siblings, 0 replies; 7+ messages in thread
From: Bruce Momjian @ 2023-11-03 17:08 UTC (permalink / raw)
To: Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>; +Cc: Tom Lane <tgl@sss.pgh.pa.us>; pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org>
On Fri, Nov 3, 2023 at 05:04:46PM +0000, Daniel Westermann (DWE) wrote:
> >"Daniel Westermann (DWE)" <daniel.westermann@dbi-services.com> writes:
> >>> Yeah, but populating it would not (unless many of the columns were
> >>> NULL).
>
> >> Ok, but then should the documentation be more precise? It seems a bit odd to
> let users create such a table without at least a warning.
>
> >Given the impact of NULLs, and the fact that usually tables have some
> >variable-width columns, I doubt that a creation-time warning could be
> >accurate enough to be useful.
>
> I am not speaking about a warning at creation time, but rather a warning in the
> docs. Something like: Although a table with e.g. 1600 bigint columns can be
> created, creating a tuple of more than 8160 bytes will fail.
It is in the "limits" docs:
https://www.postgresql.org/docs/current/limits.html
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
^ permalink raw reply [nested|flat] 7+ messages in thread
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-- links below jump to the message on this page --
2023-11-03 16:09 Incorrect mention of number of columns? Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
2023-11-03 16:12 ` Magnus Hagander <magnus@hagander.net>
2023-11-03 16:12 ` Tom Lane <tgl@sss.pgh.pa.us>
2023-11-03 16:18 ` Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
2023-11-03 16:42 ` Tom Lane <tgl@sss.pgh.pa.us>
2023-11-03 17:04 ` Daniel Westermann (DWE) <daniel.westermann@dbi-services.com>
2023-11-03 17:08 ` Bruce Momjian <bruce@momjian.us>
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