Hello,
last question to syskey :
is it possible to define foreign-keys on SYSKEY?
Thanks,
Florian Schmitz
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Zabach, Elke schrieb:
Florian Schmitz wrote:
Hello Elke,
this might be a possibility. How ist the SYSKEY-Colument incremented? ATM
i'm getting values like
'FFEE00001'.
What would be the absolute maximum of different SYSKEYs?
Each table has its own syskey-numbering -->
Each table starts with x'FF FE 00 00 00 00 00 01' and can go up to
x'FF FE FF FF FF FF FF FF' --> during the whole lifetime of such a table
281 474 976 710 656 different syskeys can be used. Overflow of this value will
not be checked. In the normal case of non-overflow, deleted syskey-values will
NOT be recycled.
Elke
SAP Labs Berlin
Thanks for your help.
Flo
Zabach, Elke schrieb:
Florian Schmitz wrote:
Hello,
i'm just thinking about different type of Primary Keys. We're actually
using randomly generated
UUIDs (GUIDs) for our "billons-of"-tables. They're stored in
VARCHAR(50)-
Columns and hence tend to
bloat space-consumption. Further i'm *guessing* they're not quite well-
performing concerning
bulk-insert and large queries.
How appropriate do you consider DEFAULT SERIAL for such large tables
(containing, or going to
contain billions of records)?
Are they're any other viable possibility for automatic created primary
keys?
Thanks alot. :-)
Flo
Did you think about our implicit primary key?
If no user-defined primary key is given, we implicitly add a (hidden)
column syskey char (8) byte, implicitly 'incremented' for each row, thus
appending the newly inserted row to the far right end of the tree of rows
in this table (as would be done with serial,too). And this behavior is
better (performance) than receiving the next serial(sequence) value and
inserting then.
You can ask for this implicitly key with
'SELECT SYSKEY,<whatever_you_like>', but SYSKEY will not be part of
'SELECT *'
Does this help?
Elke
SAP Labs Berlin
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Florian Schmitz
______________________
acardo technologies AG
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44137 Dortmund
fon: +49 (0) 2 31 / 58 44 97 - 0
fax: +49 (0) 2 31 / 58 44 97 - 21
mail: [EMAIL PROTECTED]
web: www.acardo.com
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