| From: | "Zeugswetter Andreas DCP SD" <ZeugswetterA(at)spardat(dot)at> |
|---|---|
| To: | "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Peter Eisentraut" <peter_e(at)gmx(dot)net> |
| Cc: | <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Implied Functional Index use |
| Date: | 2006-07-13 10:49:22 |
| Message-ID: | E1539E0ED7043848906A8FF995BDA579012B3EE1@m0143.s-mxs.net |
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| Lists: | pgsql-hackers |
> There is a problem of implication here, AFAICS:
> When a user SQL asks
> WHERE col1 = 7
> which equality level is meant when several exist?
Well, the operator must be unique, so there is no problem.
Unique in the sense that an operator with the same name ('=' in this
case)
and argument types cannot exist for more than one level of equality.
(and the level should not have an effect on the resolution)
So, when we see col1 = 7 we lookup the equality level of the operator
and decide whether it is strict enough for the particular optimization.
Andreas
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