| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Susanne Ebrecht <susanne(at)2ndQuadrant(dot)com> |
| Cc: | Peter Eisentraut <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Theory of operation of collation patch |
| Date: | 2011-03-08 15:15:22 |
| Message-ID: | 9236.1299597322@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Susanne Ebrecht <susanne(at)2ndQuadrant(dot)com> writes:
> On 07.03.2011 17:43, Tom Lane wrote:
>> because two expressions that are equal() must necessarily have the same collation
>> property.
> Peter, Tom,
> I am not able to see this.
> If 'abc' == 'abc' is not collation depending at all. It is only
> encoding depending.
Sorry, I was using a term of art there. This isn't about data values,
it's about parsed expression trees. See the equal() function in
src/backend/nodes/equalfuncs.c. If two expression trees match according
to equal(), then they must necessarily have the same collation property,
because equal() compares all the fields and in particular the collation
fields.
regards, tom lane
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