[Webkit-unassigned] [Bug 60746] New: IndexedDB chooses wrong record on PREV_NO_DUPLICATE index cursor

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=60746

           Summary: IndexedDB chooses wrong record on PREV_NO_DUPLICATE
                    index cursor
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: pilgrim at chromium.org
                CC: fishd at chromium.org, tony at chromium.org,
                    hans at chromium.org, dgrogan at chromium.org,
                    pilgrim at chromium.org


Original test: http://mxr.mozilla.org/mozilla2.0/source/dom/indexedDB/test/test_indexes.html?force=1

This is an adapation of part of a test from Mozilla's IndexedDB test suite. It creates an object store with several rows, creates indexes on each key, and iterates through an index cursor from end to start using the PREV_NO_DUPLICATE flag. Of two records that contain the same key in the index, the cursor chooses the wrong one. Or, at least, a different one than Mozilla chooses. Here's the spec text that pertains to PREV_NO_DUPLICATE:

"""
PREV_NO_DUPLICATE of type unsigned short
indicates that this cursor should yield all records, not including duplicates and its direction is monotonically decreasing order of keys. For every key with duplicate values, only the first record is yielded.
"""

It's not clear whether "the first record" means "the first record in decreasing order" or "the first record in increasing order." Mozilla chooses one interpretation and WebKit chooses the other.

Test case attached.

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