Juan Miguel wrote:
That would buy you absolutely nothing. char() is not faster than text.
Instead you would make everything slower because the system would
constantly have to pad and trim your values and it would bloat the storage
with the extra spaces.
First, sorry about my english.
Well ... but ... reading database theory books, you can see that fixed size
records are "better" than variant size records. When the records are size
fixed, inserts, updates and deletes can recalculate easier the position of
the rest records in the pages. These books tell you that in general cases,
variant record size tables (records that have variant type colums, for
example) imply a lower performance in the system ...
Why in postgresql these things don't matter ?
Because unlike other DBs, PostgreSQL doesn't actually remove anything when you do an update or delete, it marks the old record as "dead" and (for an update) adds a new instance of the record at the end. That's one reason why you want to vacuum tables after some activity, to remove the dead records fro all updates/deletes.
Thanks.
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