mongo collection stats size is larger than exported json

Asked Oct 25 '19 at 13:27

Active Oct 26 '19 at 13:57

Viewed 260 times

I am surprised because I import json data into mongo. As a result, the json data is noticeably smaller than the collection stats size. I did export (with mongoexport) the collection into json file again and the collection size is 2.4G when an exported json file is 1.8G. Expectation would be that the size would be at least the same as json file. Any ideas to explain that? I have not found anything in the documentation.

From docs:

collStats.size

The total uncompressed size in memory of all records in a collection. The size does not include the size of any indexes associated with the collection, which the totalIndexSize field reports.

The scale argument affects this value. Data compression does not affect this value.

MongoDB version is 4.2. The docs have never been removed or updated. The only operation was insertMany.

edited Oct 26 '19 at 13:57

asked Oct 25 '19 at 13:27

Yuki

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Is the difference maybe from removed docs? https://stackoverflow.com/questions/2966687/reducing-mongodb-database-file-size – klhr Oct 25 '19 at 15:34
No, docs have never been removed. – Yuki Oct 25 '19 at 17:19
Updated? Updates can lead to a disk page splitting into two if it increased in size – klhr Oct 26 '19 at 04:09
Neah, it is dumb sequencial inserting with batches using pymongo. – Yuki Oct 26 '19 at 13:50

mongo collection stats size is larger than exported json

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