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b95e431228
This patch fixes a bug in UpdateItem's ReturnValues=ALL_NEW, which in some cases returned the OLD (pre-modification) value of some of the attributes, instead of its NEW value. The bug was caused by a confusion in our JSON utility function, rjson::set(), which sounds like it can set any member of a map, but in fact may only be used to add a *new* member - if a member with the same name (key) already existed, the result is undefined (two values for the same key). In ReturnValues=ALL_NEW we did exactly this: we started with a copy of the original item, and then used set() to override some of the members. This is not allowed. So in this patch, we introduce a new function, rjson::replace(), which does what we previously thought that rjson::set() does - i.e., replace a member if it exists, or if not, add it. We call this function in the ReturnValues=ALL_NEW code. This patch also adds a test case that reproduces the incorrect ALL_NEW results - and gets fixed by this patch. In an upcoming patch, we should rename the confusingly-named set() functions and audit all their uses. But we don't do this in this patch yet. We just add some comments to clarify what set() does - but don't change it, and just add one new function for replace(). Fixes #9542 Signed-off-by: Nadav Har'El <nyh@scylladb.com> Message-Id: <20211104134937.40797-1-nyh@scylladb.com>