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Type: Bug
Resolution: Won't Fix
Priority: Major - P3
Fix Version/s: No version
Affects Version/s: 1.16.3, 1.28.4
Component/s: Schema
Labels:
None

Documentation Changes:
Not Needed

Compass Schema Analyser renders different graph result for a small dataset (less than 1000 documents).

Example data:

for(x=0;x<40;x++){db.test.insert({category:"foo"})}
for(x=0;x<24;x++){db.test.insert({category:"bar"})}
for(x=0;x<20;x++){db.test.insert({category:"baz"})}
for(x=0;x<15;x++){db.test.insert({category:"foz"})}
for(x=0;x<13;x++){db.test.insert({category:"for"})}
for(x=0;x<11;x++){db.test.insert({category:"bam"})}
for(x=0;x<9;x++){db.test.insert({category:"baw"})}
for(x=0;x<8;x++){db.test.insert({category:"bae"})}
for(x=0;x<7;x++){db.test.insert({category:"fog"})}
for(x=0;x<6;x++){db.test.insert({category:"com"})}
for(x=0;x<6;x++){db.test.insert({category:"cow"})}
for(x=0;x<5;x++){db.test.insert({category:"cop"})}
for(x=0;x<45;x++){db.test.insert({field:"some"})}

Test of manual $sample output:

db.test.aggregate([{$sample:{size:1000}}, {$group:{_id:"$category", count:{$sum:1}}}])

The should show that `foo` still outputs consistently of 40 documents. In Compass Schema, the percentage of value `foo` can range from 20%-28% (See screenshot)

Note that the bar shows : This report is based on a sample of 209 documents (100.00%)

MongoDB version: 4.0.5
Compass version: 1.16.3 Community