row is too big: size 8168, maximum size 8160

Hello every one!

I've found this error message and it's driving me crazy.

I have a table with 790 numeric columns, I'm trying to make an INSERT INTO
x SELECT... and in the same column/s I'm getting this message.

I've tried everything VACUUM FULL, Batch the insert with updates...but
nothing always the same error.

THe BLCKSZ is set to 8Kb here:
https://github.com/postgres/postgres/blob/master/src/include/pg_config.h.in#L36
but I'm suspecting that this or corrupted data or something I'm missing.

I've also read about TOAST-able and so on and I haven't messed with storage
properties. The data into that columns aren't big numbers (maybe having
many decimal counts)

Any clues? help?

Thank you