Correct marshalling of remotely-mapped data #4191
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| func (lm *SelectMapper) Open() error { | ||
| // If in aggregate mode, initialize the map-and-reduce functions. Both local and | ||
| // remote mappers need this. | ||
| if !lm.rawMode { |
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This was moved up here because it now needs to be done before the remote mapper is opened.
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+1 |
[ci skip]
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Comment corrected @corylanou Merging now. |
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Correct marshalling of remotely-mapped data
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The fundamental problem was over-use of
interface{}which was preventing proper unmarshalling. This change instead makes use of[]byteand[][]bytewhere necessary, so proper unmarshalling takes place on the local side. This is how the code operated before the DQ-refactor, but this bug was not caught since only some aggregate functions were affected by the bug.countandsumworked fine in DQ mode, butmean(for example) did not.The other key change is making the correct unmarshalling functions available to the remote mapper code. Without this change, a fix was impossible since the remote mapper wouldn't know the correct types, e.g.
meanMapOutputfor the unmarshalling of aggregate data.This solution is not ideal, but more changes are due in this area very soon, so this patch aims to work with the existing framework.
I tested this by setting a single-node into forced-remote mapping mode and ran
meanqueries. Before this fix, the system panicked with the trace in #4170. With the fix in place, everything works fine.Fixes #4170