#2324: Increase length of Permission.permission_name
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Reporter: pitrou | Owner:
Type: defect | Status: new
Priority: normal | Milestone:
Component: TurboGears | Version: 2.0b7
Severity: trivial | Resolution:
Keywords: |
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Comment (by pitrou):
I question both the meaning and relevance you give to these documents:
- The Oracle example is for a table of 8,388,608 rows (!)
- The MySQL doc says "When MySQL will need to do the sort it will use
corresponding fixed length field format, which will lead to larger
temporary file and so slower sorting.". Sure, but you don't sort
permissions by permission_name. Actually, you don't sort permissions at
all.
- As for the MS SQL docs, they don't explicitly state that VARCHAR with a
large size are a bad thing. They seem to talk about size of fixed-length
columns.
In any case, the fact that a typical application will only have 5 to 10
different permissions, and the richest applications perhaps 50 to 100 of
them, seems to make the whole objection gratuitous. Querying such a data
set will be blazingly fast, whatever the exact column types, on any decent
DBMS.
Ironically, the fact that no Index is defined in model/auth.py is probably
much more detrimental to performance (for non-trivial datasets) than the
size of the various columns.
(PostgreSQL doesn't automatically create an index for each foreign key ;
you have to manually create indexes yourself if you want to speed up joins
along those foreign keys. "EXPLAIN SELECT" tells me that currently,
PostgreSQL will do a sequential scan when joining between the various auth
tables)
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Ticket URL: <http://trac.turbogears.org/ticket/2324#comment:4>
TurboGears <http://www.turbogears.org/>
TurboGears front-to-back web development
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