Alex Behm has posted comments on this change. Change subject: IMPALA-4787: Optimize APPX_MEDIAN() memory usage ......................................................................
Patch Set 4: (6 comments) I'm pretty happy with this patch. http://gerrit.cloudera.org:8080/#/c/6025/4/be/src/exprs/aggregate-functions-ir.cc File be/src/exprs/aggregate-functions-ir.cc: Line 1025: // can fit 10 times as many samples, up to a maximum of MAX_NUM_SAMPLES. We do not update references to '10' Line 1026: // allocate room for MAX_NUM_SAMPLES samples up front in order to conserve memory. in order to -> to Line 1031: if (new_capacity * 2 >= MAX_NUM_SAMPLES) new_capacity = MAX_NUM_SAMPLES; DCHECK_LT(state->capacity, new_capacity); in case someone decides to significantly muck with the sampling constants such that this can overflow Line 1051: // ReservoirSamples. Initially, the array has enough room for MAX_NUM_SAMPLES / 1000 update to reflect the new initial size Line 1063: *state = ReservoirSampleState<T>(); It would be clearer what's happening if we added a constructor for ReservoirSampleState that initializes the struct fields. Right now, it appears that num_samples and source_size could be uninitialized. Line 1076: // If the container is full, increase it's size by 10x. update 10 -- To view, visit http://gerrit.cloudera.org:8080/6025 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: comment Gerrit-Change-Id: I99adaad574d4fb0a3cf38c6cbad8b2a23df12968 Gerrit-PatchSet: 4 Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-Owner: Taras Bobrovytsky <[email protected]> Gerrit-Reviewer: Alex Behm <[email protected]> Gerrit-Reviewer: Marcel Kornacker <[email protected]> Gerrit-Reviewer: Matthew Jacobs <[email protected]> Gerrit-Reviewer: Mostafa Mokhtar <[email protected]> Gerrit-Reviewer: Taras Bobrovytsky <[email protected]> Gerrit-HasComments: Yes
