The option with

T1: A B C and T2 A D (to avoid the updates)
works very well with a simple query

Insert into T2 (A, D)
select A, functionToGetD from T1 left join T2 on T1.A = T2.A
where T2.A is null

The above gives me the new records for those where D was not filled yet.
Since they are all new records, I have no trouble with the MVCC

On 21 Aug 2005, at 21:06, Jeffrey W. Baker wrote:

On Sun, 2005-08-21 at 20:32 +0200, Yves Vindevogel wrote:


Say I have a table with column A, B, C, D
A has a unique index on it (primary key)
B and C have a normal index on it
D has no index

If I perform a query like update tbl set D = 'whatever' ;
that should make no difference on the indexes on the other columns,
right ?

What postgresql does on update is to make a new record, so there will be
two records in your table and two records in your index. You would need
to vacuum the table to mark the space for the old record free, and you
would need to reindex the table to shrink the index.

Or is there some kind of mechanism that does create a sort of new
record, thus makes the indexes go wild.



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Met vriendelijke groeten,
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Kind regards,

Yves Vindevogel

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