I use a DateProperty field with auto_add = True and indexed = True all the time to enable querying a section of records. AFAIK this is likely the best way for doing things like "process all of yesterday's invoices that were booked between 10:00-11:00". Unfortunately it often requires the use of a custom index because you are going to add an order clause on the query. That adds to your write and index overhead costs, and gets you involved with eventual consistency issues. This is all very different from the complex issues related to how to create a true, monotonically increasing value. (The date index should work for most use cases if some records get the same create date.) If you absolutely must have a unique field value, then you are into the more complex monotonic issue for which I have yet to read a really good solution at very high QPS. (I only dream of such issues, my practical reality more often involves QPM :-)
There are some circumstances I have encountered when using an indexed date field where it would be very helpful to know how the eventual consistency of the index gets worked out. If anyone has insights into this, please consider my SO question. thx -stevep SO Link: http://stackoverflow.com/questions/9357068/do-composite-index-updates-maintain-same-order-as-original-updates On May 7, 6:01 am, Michael Hermus <michael.her...@gmail.com> wrote: > All, > > I have read in several places that using a monotonically increasing > value for a key or in an index is a bad thing, primarily because of > the way Big Table manages the process of splitting overloaded tablets. > In a few comments, I have read that it really isn't an issue unless > you hit around 300 QPS. > > There are many cases where I would like to use timestamp in an index > (to order or limit query results based on creation time, for example). > So, my questions are: > > 1) Is there a definitive issue with throughput when using a timestamp > in an index? > 2) If yes, what is the approximate QPS threshold where it becomes an > problem? > 3) What can we expect after exceeding this threshold? > > Thanks in advance! -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
