Now that there are 3 different commands being routed to tools/volt it might be better to have one if statement that checks all 3 keywords. The best thing might be to have a variable at the top with the list as the value and then the if statement never needs to change again. You would only have to maintain the array variable and it's more visible near the top of the file. E.g.

    declare -a VOLT_KEYWORDS=(compile mask collect)
    ...
    for (( i=0; i < ${#VOLT_KEYWORDS[@]}; i++ )); do
        if [ "$1" = "${VOLT_KEYWORDS[$i]}" ]; then
            exec $VOLTDB_HOME/tools/volt "$@"
        fi
    done