That’s all that’s needed, really. It’s impossible to make an informed decision if there is no way for someone to know what a table rewrite actually does and how it does it.
/*---------------------------------------------------------------------------------*/
float o=0.075,h=1.5,T,r,O,l,I;/* Ilsa Loving */int _,L=80,s=3200; int main()
{for(;s%L||(h-=o,T=-2),s;4-(r=/* IT Manager */O*O)<(l=I*I)|++ _==L&&
write(1,(--s%L?_<L?--_%6:6:7) /* The Jonah Group */+"Ilsa L.\n",1)&&(O=I=l=_=r=0,
T+=o /2))O=I*2*O+h,I=l+T-r;} /* 416-304-0860x227 */
On 20 Jan 2018, at 22:47, Alvaro Herrera wrote:
Michael Paquier wrote:
On Fri, Jan 19, 2018 at 11:33:43AM -0500, Tom Lane wrote:
It means reading the whole table and writing it out in some modified
form (for instance, with some column transformed into a new datatype).
It's not "dangerous" in any way ... but if you've got many GB of data in
the table and you can't afford to have the table locked for a long time,
then it's something to avoid.
Yeah that can be costly. Note that WAL corresponding to this data needs
to be generated as well.
Maybe we need to document this somewhere, particularly now that we have
a "table_rewrite" event item.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
