On 06/25/2013 06:41 PM, Tom Lane wrote:
>> Well, it was more in the form of:
>> tab1.x = COALESCE(tab2.y,tab1.x)
>
> Hm. I'm not following how you get from there to complaining about not
> being smart about X = X, because that surely ain't the same.
Actually, it was dominated by defaultsel, sinc
Josh Berkus writes:
>> Personally, I'll bet lunch that that external software is outright
>> broken, ie it probably thinks "X = X" is constant true and they found
>> they could save two lines of code and a few machine cycles by emitting
>> that rather than not emitting anything.
> Well, it was mo
> Personally, I'll bet lunch that that external software is outright
> broken, ie it probably thinks "X = X" is constant true and they found
> they could save two lines of code and a few machine cycles by emitting
> that rather than not emitting anything. Of course, the amount of
> parsing/planni
Josh Berkus writes:
> On 06/21/2013 02:32 PM, Tom Lane wrote:
>> See DEFAULT_EQ_SEL.
> Why is it using that? We have statistics on the column. What reason
> would it have for using a default estimate?
The stats are generally consulted for "Var Op Constant" scenarios.
It doesn't know what to
On 06/21/2013 02:32 PM, Tom Lane wrote:
> Josh Berkus writes:
>> I'm getting something really odd in 9.2.4, where the planner estimates
>> that the selectivity of a column equal to itself is always exactly 0.5%
>> (i.e. 0.005X). I can't figure out where this constant is coming from,
>> or why it'
Josh Berkus writes:
> I'm getting something really odd in 9.2.4, where the planner estimates
> that the selectivity of a column equal to itself is always exactly 0.5%
> (i.e. 0.005X). I can't figure out where this constant is coming from,
> or why it's being applied.
See DEFAULT_EQ_SEL. But why
