EraseTable erases a table, often a good way to reduce garbage creation. Note that erasing a table can be more expensive than letting the GC system reclaim it, so one might prefer simply reallocating a new empty table. Also, note that a hash (as opposed to a 1..n integer-index) will NEVER SHRINK. Each key you ever used will use ~40 bytes and keep doing so until the table is destroyed. If you re-use the same keys this is obviously a nonissue.
For more details on the inner workings of tables and when to reallocate vs when to erase, see Lua object memory sizes and it's talk page.
local function EraseTable(t) for i in pairs(t) do t[i] = nil end end