#2 Why has PostgreSQL 'weak ALTER TABLE support'?

[Karsten Dambekalns]

I might sound a bit stupid, but I read this phrase a
few times now, and I would love to know what exactly
makes it harder to do this on PostgreSQL compared to
e.g. MySQL.

Could you explain it to me? Or give some pointers to
documentation?

Thanks, and by the way: Great piece of software!
Karsten

[Richard Tango-Lowy]

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Never answered this. Sorry Karsten! MySQL and Oracle can
rename columns, change field types, etc. Postgres' ALTER
TABLE functionality is rather more limited.

One day soon, I'll finish the code to use table replacement
rather than ALTERing to upgrade the schema in a postgres DB.

Rich

[Karsten Dambekalns]

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No problem...
I'd like to help with this, but I guess it should be done in
ADODB itself rather than in axmls, no?

[Richard Tango-Lowy]

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I suggested such to John Lim at adodb. He said it would be
non-trivial, but he knows it needs to be done.

[Richard Tango-Lowy]

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We can use the create-copy-drop method to change a table.
The issue is whether or not sequences will get broken during
the upgrade. I think there are some ways to work around this.

[Karsten Dambekalns]

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Create-Copy-Drop sounds good, but we should probably try to
check if we really need to do this. As far as I can see, on
upgrading a table (on MySQL at least), the whole structure
is 'touched'.
This isn't a problem on MySQL, as it knows to do changes
only when it's needed.
If we create-copy-drop manually, and there is a lot of data
in a table, this might be error-prone and take potentially a
lot of time, so we should do it only if needed...
Do you have any plans already on how to do all this? If (and
if not as well), this should be taken to the mailing list :)