Decks, Patios, Porches and Docks - Supporting the old pillars

How do I support the wooden pillars while replacing the porch floor and floor supports? Common sense tells me the 100 year old porch pillars will separate once the roof is started to raise and most likely fall apart.
I had thought of putting ratchet straps around them to hold them together and possibly some more to hold them up tight to the roof during reconstruction. Any ideas?

Use posts set on hydraulic jacks (sitting on large blocks of wood like chunks of rail road ties or similar so they won't sink into the ground) to take the weight off of the old posts. You aren't raising the roof, just transferring the load to the temporary posts, so it won't harm the roof structure at all. Work one post at a time.

problem is I will be raising the roof approximately 6 inches back to it original height and I fear the pillars will fall apart once the roof is lifted off them.
The floor is basically gone and since the pillars are most likely nailed to the cieling of the roof I dont want to dislodge them if not necessary. This house was an inheritance, in sad repair and this is the only task I haven't tackled before.
The pillars rest on a beam connected to the exterior foundation wall covered by floor boards and each of the 8 pillars are about 2 feet across 10 feet tall and made of several slats.
Raising the roof and replacing the beam and floor is easy but the pillars have me concerned how to keep them together.

The roof has come down 6"??

Oh, now that's serious -- a lot more than I was assuming.

it needs to be put back to its original height. If has dropped 6", the damage is done. Raising it back up probably isn't an option. if the 6" drop didn't destroy it, the 6" raise most certainly will. My suggestion is to tear it out completely and rebuild it.