Re: Speed & Memory Management

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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