Redis - Is there a limit on SET for datatype STRING?

redis-cli uses linenoise custom library for terminal input, which happens to have hard-coded input buffer size of 4096 bytes: linenoise.c:101. You may want to write down your Redis command into a file and execute it with redis-cli --eval.

You can use -x option to read value from stdin

redis-cli -x -h localhost -p 6379 set my-key < /path/to/file.txt