An evicted page will be freed from memory (garbage
collected) if the user of this class has not retained a
reference to it; otherwise it simply no longer counts towards
the maximum cache size.
Returns the number of entries in the tree with a key between
min and max inclusive; if either min or max is null it is treated
as negative or positive infinity (respectively)
Creates space in the cache for pageid, but only actually reads
the bytes if readBytes is true; if the page was not already
in the cache and readBytes is false, subsequent calls to
setDirty()/flush() will overwrite data previously on the page.