On Sun, Sep 10, 2017 at 10:42 AM Merlin Moncure <mmoncure@xxxxxxxxx> wrote:
On Friday, September 8, 2017, John Turner <fenwayriffs@xxxxxxxxx> wrote:On Fri, Sep 8, 2017 at 6:57 AM Tom Lane <tgl@xxxxxxxxxxxxx> wrote:Ron Johnson <ron.l.johnson@xxxxxxx> writes:
> Based on LENGTH(offending_column), none of the values are more than 144
> bytes in this 44.2M row table. Even though VARCHAR is, by definition,
> variable length, are there any internal design issues which would make
> things more efficient if it were dropped to, for example, VARCHAR(256)?
No.So the declarative column length has no bearing on memory grants during plan generation/execution?Nope. Memory usage is proportional to the size of the string, not the maximum length for varchar. Maximum length is a constraint.
Ok, thanks for verifying. I was curious since other platforms seem to handle this aspect of memory allocation differently (more crudely, perhaps) based on estimation of how fully populated the column _might_ be given a size constraint:
John
