ForestDB: Emitting dictionary key causes error

[24601]

When running a query against a FORESTDB couchbase lite db (new or upgraded, happens on both), getting a "FORESTDB ERROR -1" when calling run on the CBLQuery object to get the CBLQueryEnumerator.

Specifically:

CBLQuery* statuteComponents = [statuteComponentsByCitation createQuery];

CBLQueryEnumerator* results = [statuteComponents run:&error];

creates:

FORESTDB ERROR -1
(lldb) bt
* thread #1: tid = 0x1e8c03, 0x000000010669e519 libc++abi.dylib`__cxa_throw, queue = 'com.apple.root.default-qos', stop reason = breakpoint 1.2
    frame #0: 0x000000010669e519 libc++abi.dylib`__cxa_throw
    frame #1: 0x0000000101de82c5 Voltaire`forestdb::Transaction::set(forestdb::slice, forestdb::slice, forestdb::slice) + 309
    frame #2: 0x0000000101df5088 Voltaire`forestdb::IndexTransaction::update(forestdb::slice, unsigned long long, std::__1::vector<forestdb::Collatable, std::__1::allocator<forestdb::Collatable> >, std::__1::vector<forestdb::Collatable, std::__1::allocator<forestdb::Collatable> >, unsigned long long&) + 568
    frame #3: 0x0000000101deb941 Voltaire`forestdb::MapReduceIndex::updateDocInIndex(forestdb::IndexTransaction&, forestdb::Mappable const&) + 225
    frame #4: 0x00000001067d5825 libdispatch.dylib`_dispatch_client_callout2 + 8
    frame #5: 0x00000001067c2c54 libdispatch.dylib`_dispatch_apply_serial + 56
    frame #6: 0x00000001067d57f4 libdispatch.dylib`_dispatch_client_callout + 8
    frame #7: 0x00000001067bcb64 libdispatch.dylib`_dispatch_sync_f_invoke + 303
    frame #8: 0x00000001067c28df libdispatch.dylib`dispatch_apply_f + 306
    frame #9: 0x0000000101dec76e Voltaire`forestdb::MapReduceDispatchIndexer::addMappable(forestdb::Mappable const&) + 94
    frame #10: 0x0000000101de5933 Voltaire`___lldb_unnamed_function2794$$Voltaire + 255
    frame #11: 0x0000000101debdd5 Voltaire`forestdb::MapReduceIndexer::run() + 405
    frame #12: 0x0000000101daaeb2 Voltaire`___lldb_unnamed_function1488$$Voltaire + 571
    frame #13: 0x0000000101daa71e Voltaire`___lldb_unnamed_function1476$$Voltaire + 88
    frame #14: 0x0000000101da3423 Voltaire`___lldb_unnamed_function1339$$Voltaire + 395
    frame #15: 0x0000000101da0165 Voltaire`___lldb_unnamed_function1227$$Voltaire + 153
  * frame #16: 0x0000000101c95574 Voltaire`+[VTAccountViewController doDataLoadStatic](self=0x000000010258ccc8, _cmd=0x0000000102279bde) + 3028 at VTAccountViewController.m:130
    frame #17: 0x0000000101c8f89b Voltaire`__40-[VTLoginFormViewController viewDidLoad]_block_invoke255(.block_descriptor=<unavailable>) + 667 at VTLoginFormViewController.m:178
    frame #18: 0x0000000101e8c9b9 Voltaire`-[BPFormButtonCell buttonPressed:](self=0x00007ff01b1c1b60, _cmd=0x0000000104dd0354, sender=0x00007ff01b1469a0) + 137 at BPFormButtonCell.m:81
    frame #19: 0x0000000104577e6e UIKit`-[UIApplication sendAction:to:from:forEvent:] + 75
    frame #20: 0x000000010467e9c0 UIKit`-[UIControl _sendActionsForEvents:withEvent:] + 467
    frame #21: 0x000000010467dd8f UIKit`-[UIControl touchesEnded:withEvent:] + 522
    frame #22: 0x00000001049247d0 UIKit`_UIGestureRecognizerUpdate + 9487
    frame #23: 0x00000001045bd5a6 UIKit`-[UIWindow _sendGesturesForEvent:] + 1041
    frame #24: 0x00000001045be1d3 UIKit`-[UIWindow sendEvent:] + 667
    frame #25: 0x000000010458af61 UIKit`-[UIApplication sendEvent:] + 246
    frame #26: 0x000000010459802d UIKit`_UIApplicationHandleEventFromQueueEvent + 17370
    frame #27: 0x00000001045736b3 UIKit`_UIApplicationHandleEventQueue + 1961
    frame #28: 0x00000001061d7551 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    frame #29: 0x00000001061cd41d CoreFoundation`__CFRunLoopDoSources0 + 269
    frame #30: 0x00000001061cca54 CoreFoundation`__CFRunLoopRun + 868
    frame #31: 0x00000001061cc486 CoreFoundation`CFRunLoopRunSpecific + 470
    frame #32: 0x00000001079949f0 GraphicsServices`GSEventRunModal + 161
    frame #33: 0x00000001045769d0 UIKit`UIApplicationMain + 1282
    frame #34: 0x0000000101c9f413 Voltaire`main(argc=1, argv=0x00007fff5e0104a8) + 115 at main.m:19
    frame #35: 0x000000010680a145 libdyld.dylib`start + 1

The view creation code looks like this:

CBLView* statuteComponentsByCitation = [self.cblDatabase viewNamed:@"statuteComponents"];

[statuteComponentsByCitation setMapBlock: MAPBLOCK({
    // NSLog(@"map function for casesByName got doc: %@",[doc description]);
    if([[doc valueForKey:@"type"] isEqualToString:@"VTStatuteComponent"])
    {

            emit(doc,[doc valueForKey:@"citation"]);
    }
}) version:@"3"];

(obviously, this should be open against the forestdb branch)

[snej]

I think you put the parameters to emit backwards — it's (key, value) not (value, key).

What you've done shouldn't crash (though it's unlikely to do anything useful), but since doc is an NSDictionary it means the index key is a JSON dictionary/map/object instead of a scalar or array. This hasn't been tested in CBL since it's almost never done, as dictionaries don't make useful index keys.

I should figure out why this is crashing and make it not crash, but if you fix your emit call this won't happen anymore.

[24601]

Yup, that was a bonehead move on my part :), thanks for catching the error on my part!

[snej]

That's error FDB_RESULT_INVALID_ARGS from fdb_set(). Not sure why that would happen; empty key?

[snej]

Actually it was probably a too-long key; currently ForestDB's maximum key length is 3840 bytes (FDB_MAX_KEYLEN). We should handle or at least report this better, since I think other developers may run into it.

[snej]

The latest commit (4884ae7) logs a specific warning in this case, and just skips emitting that one key/value pair instead of aborting the whole index update.