It runs the same as a nested select. Currently, since Hive doesn't do any relational common subexpression elimination, it will be executed twice. In the example below, this can be a good thing, since cond1 and cond2 can be pushed down separately.
JVS On Dec 28, 2010, at 12:18 AM, Neil Xu wrote: > in hive 0.6, we can create view for tables, views are actually run as a > subquery when querying data, is it optimized in hive that a view is executed > only once in a single query? Thanks in advance! > such as: > select * > from ( > select x,y > from view1 > where cond1 > > union all > > select x,y > from view1 > where cond2 > ) > > Neil, >
