I have been using these documents for a couple weeks, implementing various store and load functionality, and they have been very helpful.
However, there is room for improvement. What is most unclear is when the API methods get called. Each method should clearly state in these documents (and the javadoc) when it is called -- front-end only? back-end only? both? Sometimes this is obvious, other times it is not. For example, without looking at the source code its not possible to tell or infer if pushProjection() is called on the front-end or back-end, or both. It could be implemented by being called on the front-end, expecting the loader implementation to persist necessary state to UDFContext for the back-end, or be called only on the back-end, or both. One has to look at PigStorage source to see that it persists the pushProjection information into UDFContext, so its _probably_ only called on the front-end. There are also a few types that these interfaces return or are provided that are completely undocumented. I had to look at the source code to figure out what ResourceStatistics does, and how ResourceSchema should be used. RequiredField, RequiredFieldList, and RequiredFieldResponse are all poorly documented aspects of a public interface. On May 21, 2010, at 11:42 AM, Pradeep Kamath wrote: > To add to this, there is also a how-to document on how to go about > writing load/store functions from scratch in Pig 0.7 at > http://wiki.apache.org/pig/Pig070LoadStoreHowTo. > > Pradeep > > -----Original Message----- > From: Alan Gates [mailto:[email protected]] > Sent: Friday, May 21, 2010 11:33 AM > To: [email protected] > Cc: Eli Collins > Subject: Pig loader 0.6 to 0.7 migration guide > > At the Bay Area HUG on Wednesday someone (Eli I think, though I might > be remembering incorrectly) asked if there was a migration guide for > moving Pig load and store functions from 0.6 to 0.7. I said there was > but I couldn't remember if it had been posted yet or not. In fact it > had already been posted to > http://wiki.apache.org/pig/LoadStoreMigrationGuide > . Also, you can find the list of all incompatible changes for 0.7 at > http://wiki.apache.org/pig/Pig070IncompatibleChanges > . Sorry, I should have included those links in my original slides. > > Alan.
