Re: Avoid index rebuilds for no-rewrite ALTER TABLE ALTER TYPE

On Thu, Jul 7, 2011 at 3:25 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Thu, Jul 7, 2011 at 3:21 PM, Noah Misch <noah(at)2ndquadrant(dot)com> wrote:
>> On Thu, Jul 07, 2011 at 03:06:46PM -0400, Robert Haas wrote:
>>> On Thu, Jul 7, 2011 at 2:55 PM, Noah Misch <noah(at)2ndquadrant(dot)com> wrote:
>>> > CheckIndexCompatible() calls ComputeIndexAttrs() to resolve the new operator
>>> > classes, collations and exclusion operators for each index column.  It then
>>> > checks those against the existing values for the same.  I figured that was
>>> > obvious enough, but do you want a new version noting that?
>>>
>>> I guess one question I had was... are we depending on the fact that
>>> ComputeIndexAttrs() performs a bunch of internal sanity checks?  Or
>>> are we just expecting those to always pass, and we're going to examine
>>> the outputs after the fact?
>>
>> Those checks can fail; consider an explicit operator class or collation that
>> does not support the destination type.  At that stage, we neither rely on those
>> checks nor mind if they do fire.  If we somehow miss the problem at that stage,
>> DefineIndex() will detect it later.  Likewise, if we hit an error in
>> CheckIndexCompatible(), we would also hit it later in DefineIndex().
>
> OK.

Committed with minor comment and documentation changes.

--
Robert Haas
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