The problem is, you suddenly have an onus to be polite about it.
"I have a concern that this may not be feasible".
"No, you just have to try harder!"
"Sorry, I wasn't very clear: This is flat out impossible".
"Are you sure?"
"Yes, because google tried, and couldn't do it. You see, it's actually impossible to get the (technical mumbo jumbo) so it will take literally years to run a single query."
And this isn't a typical case. The most likely case is you suspect that the boss is leading everyone into the valley of death, but can't prove it. Do you confront them yourself, try to sound out other colleagues (who may have other concerns, since it's not their problem), or just warn them that there's likely to be problems, and gradually manage their expectations?
In an ideal world, bosses are good at both ferreting out concerns fro indirect hints ("I'm a bit worried that"), and dealing with direct statements ("It's impossible, you git!"). In reality, they are often just wage slaves who kiss up and kick down, and don't really care if the project flops as long as someone else is to blame.
"I have a concern that this may not be feasible".
"No, you just have to try harder!"
"Sorry, I wasn't very clear: This is flat out impossible".
"Are you sure?"
"Yes, because google tried, and couldn't do it. You see, it's actually impossible to get the (technical mumbo jumbo) so it will take literally years to run a single query."
And this isn't a typical case. The most likely case is you suspect that the boss is leading everyone into the valley of death, but can't prove it. Do you confront them yourself, try to sound out other colleagues (who may have other concerns, since it's not their problem), or just warn them that there's likely to be problems, and gradually manage their expectations?
In an ideal world, bosses are good at both ferreting out concerns fro indirect hints ("I'm a bit worried that"), and dealing with direct statements ("It's impossible, you git!"). In reality, they are often just wage slaves who kiss up and kick down, and don't really care if the project flops as long as someone else is to blame.