hive-variables are interpreted by the CLI before the query parser. If your using hive 0.8. you should upgrade. You can benefit hive's macro system.
On Tue, Oct 15, 2013 at 5:49 AM, Ed Soniat <eson...@liveperson.com> wrote: > Hive variables do not seem to be evaluated by the assigned expression, so > they seem to be macros not variables. > > Let us say I want to have a variable called secondsInADay and for clarity > set it thus set secondsInADay=24*60*60; > > To the best of my ability to determine secondsInADay will perform the > calculation each time it is referenced, it will not be bound to 86400 but > will be bound to 24*60*60 and could be evaluated billions of times. > > This is has ramifications if I am using a date in a variable. Lets say I > start a set of selects using a variable set thus, > > set priviousDay=<some code to use current date/time to calculate a > previous date/time> > > And the queries referencing this previousDay variable were to execute > across the servers day. The queries would reference different previous days > because the variable is being evaluated in the query not at the assignment. > > Is this an accurate assessment and can it be avoided? > > Short of creating a table of values of variable evaluations, which > wouldn't be a very pretty thing with which to join, not to mention my hive > is pre .8 and only has overwrite so I doubt even that is feasible without > of creating one table per variable (yuk). > > Thank you for considering my question. > > This message may contain confidential and/or privileged information. > If you are not the addressee or authorized to receive this on behalf of > the addressee you must not use, copy, disclose or take action based on this > message or any information herein. > If you have received this message in error, please advise the sender > immediately by reply email and delete this message. Thank you. >
