Hi, In a nutshell, (1) a column store will only touch the columns on disk as needed and (2) MonetDB will memory map them upon need leaving the details to the operating system. For the full story, see the (scientific) background literature. http://www.monetdb.org/Home/ScienceLibrary regards, Martin On 3/21/13 1:43 PM, Hassan, Ahmad wrote:
Hi Team,
Please may I ask what main memory management strategy has been adopted for MonetDB in terms of memory utilization. For example I loaded the TPCH benchmark dataset in MonetDB (v11.13.5) with scale factor 40. The data on disk is 43Gb in size. But when I run the TPCH queries then the main memory used by mserver stays in the range of 0.5GB to 3GB.
I was thinking that the monetDB would load the tables into memory because TPCH queries are doing joins over various tables but it seems that monetdb loads only small subset of the complete dataset.
Please can someone explain what is going in the background and why I always see 0.5GB to 3GB memory resident size of mserver process even for dataset of size 43G and if this is the normal expected behaviour of monetdb?
The farm size on disk is:
farms/f1/db1/bat# du . -hs
48G .
Thanks.
Kind Regards, Ahmad
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