On 2017-01-04 06:53:31 -0800, Adrian Klaver wrote:
> On 01/04/2017 05:00 AM, vod vos wrote:
> >Now I am confused about I can create 1100 columns in a table in
> >postgresql, but I can't copy 1100 values into the table. And I really
>
> As pointed out previously:
>
> https://www.postgresql.org/about/
> Maximum Columns per Table 250 - 1600 depending on column types
>
> That being dependent on both the number of columns and the actual data in
> the columns.
I think this is confusingly phrased. In my mind "column type" is static
- the type is the same, independent of the values which are stored. So
"250 - 1600 depending on column types" implies to me that there is
some type A of which I can have only 250 columns and another type B of
which I can have 1600 columns. But it doesn't imply to me that the
number of columns depends on the values which ar put into those columns.
May I suggest the these improvements?
In https://www.postgresql.org/about/:
Instead of
| 250 - 1600 depending on column types
write
| 250 - 1600 depending on column types and data
In https://www.postgresql.org/docs/9.6/static/ddl-basics.html:
Replace the sentence:
| Depending on the column types, it is between 250 and 1600.
with:
| For all columns in a row, some information (either the data itself or
| a pointer to the data) must be stored in a single block (8 kB).
| Because for some types this data is itself of variable length, the
| maximum number of columns depends not only on the types of the columns
| but also on the data (e.g., a NULL uses less space than a non-NULL
| value). Therefore there is no simple way to compute the maximum number
| of columns, and it is possible to declare a table with more columns
| than can be filled. Keeping all this in mind, the limit is between 250
| and 1600.
hp
--
_ | Peter J. Holzer | A coding theorist is someone who doesn't
|_|_) | | think Alice is crazy.
| | | hjp@hjp.at | -- John Gordon
__/ | http://www.hjp.at/ | http://downlode.org/Etext/alicebob.html
