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From "Marcel Kornacker (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-4787: Optimize APPX MEDIAN() memory usage
Date Fri, 10 Mar 2017 17:10:38 GMT
Marcel Kornacker has posted comments on this change.

Change subject: IMPALA-4787: Optimize APPX_MEDIAN() memory usage

Patch Set 14:

File be/src/exprs/

Line 908: const static int INIT_CAPACITY = 16;
move those constants into the classes that use them

Line 981: // stored in a dynamically sized array. See the ".h" file for more details.
briefly describe memory mgmt, in particular the switch to the inlined representation.

i didn't get the "see .h for more details part", is there anything relevant to this in there?

Line 1040:   // contains. Frees the memory of the current object. Requires a call Deserialize()
fix grammar

point out that the array must not be inlined

Line 1062:     DCHECK(!sample_array_inline_);
dcheck this at the top, makes it easier to pick up on it.

Line 1085:   // reservoir sampling algorithm.
point out all side effects (increase of capacity; when that fails)

Line 1100:     // First, fill up the dst samples if they don't already exist. The samples
are now
separate logically separate blocks with blank lines

Line 1124:     if (num_samples_ == 0) {
single line

Line 1138:   void Free(FunctionContext* ctx) {
call this Delete, because that's what it basically implements (free() only frees the memory
directly allocated for that pointer)

Line 1151:   // resize occurs, this needs to be updated.
i'm assuming this is the size of the array. comment.

Line 1169:   // Increases the size of the samples array to a rounded up to a power of two
"array to new_capacity, rounded up to a power of two."

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Gerrit-MessageType: comment
Gerrit-Change-Id: I99adaad574d4fb0a3cf38c6cbad8b2a23df12968
Gerrit-PatchSet: 14
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Taras Bobrovytsky <>
Gerrit-Reviewer: Alex Behm <>
Gerrit-Reviewer: Jim Apple <>
Gerrit-Reviewer: Marcel Kornacker <>
Gerrit-Reviewer: Matthew Jacobs <>
Gerrit-Reviewer: Mostafa Mokhtar <>
Gerrit-Reviewer: Taras Bobrovytsky <>
Gerrit-HasComments: Yes

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