There are several places in the code where comma-ok map retrieval was
being used poorly. Some were benign, like checking existence before
issuing an unconditional delete with no cleanup. Others were potentially
far more serious: assuming that if 'ok' was true, then the resulting
pointer retrieved from the map would be non-nil. `nil` is a perfectly
valid value to store in a map of pointers, and the comma-ok syntax is
meant for when membership is distinct from having a non-zero value.
There was only one or two cases that I saw that being used correctly for
maps of pointers.
This change provides a clear separation between the query engine
mechanics and the query language so that the language can be parsed and
dealt with separate from the query engine itself.
Joe LeGasse
Jonathan A. Sternberg