The commits of the mergeChunks and _configsvrMergeAllChunksOnShard commands include two query statements (1, 2) to select all the pre-existing chunks within a range (using the chunkDoc.min field to define the boundaries).

 These statements are nevertheless expressed in a non-canonical way.

Instead of declaring a single statement

{minField: {$lte: lowerBoundValue, $gt: upperBound}} 

They are encoded as two statements (evaluated in and) over the same field name

 minField: {$lte:: lowerBoundValue}, 
 minField: {$gt: upperBoundValue}

The objective of this ticket is to re-establish the canonical form.