Both in eZContentTreenNode and in eZSearch this function is used where a 'like' would be much faster.

Reason is simple, sql 'substring' does not use index while 'like' does!
(Tested in mysql and oracle)

Example from eZSearch:

( substring( ezcontentobject_tree.path_string from 1 for 18 ) = '/1/2/481950/66/72/' )

Should be something like:

( ezcontentobject_tree.path_string like '/1/2/481950/66/72/%' )