Re: Columnar Storage layout of MonetDB

On 21 Mar 2017, at 06:04, Senthil Vidhiyakar wrote:

I want to know the pattern in which the columns are stored in each file. I mean the arrangement of data in a column in that file.

Hai, The pattern is simple. Each column is stored in one file. within one file, data are stored in the order they were added, as a single C-array.

How monetdb determines offset to select a particular row, header and footer format and other details like that.

I don’t know what you mean with “header and footer format”, but determining the selected row is a complicated process, which depends on the data, query and whether some secondary indices can/should be used… Regards, Jennie

On Mon, Mar 20, 2017 at 5:59 PM, Eyal Rozenberg wrote:

The layout is actually rather involved, especially if you want to know about how the structure changes/files get created or moved during the course of a run of the mserver5 process; or how SQL columns relate to BAT columns; etc.

Also - the file layout changes with newer versions of MonetDB, and specifically, there was a significant change with version 11.25 (Dec 2016) - BATs are now always headless, so the format does not support storing actual heads.

In light of the above - can you try to describe your interests slightly more specifically?

Eyal

On 03/20/2017 12:58 PM, Senthil Vidhiyakar wrote: I want to know the file layout of columnar data storage in MonetDB. I know each column is stored in separate files. Actually I want to know the exact layout as in a block diagram to get a clear picture of the storage layout. Helps are appreciated.

Regards, Senthil Vidhiyakar. S

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