A user reported that he has a 4-node ColumnStore system, with 4 PMs. He noticed that the rows for one of his tables is distributed across all PMs:

select count(*) from tab where idbdbroot(measure_id)=1 -- 691588600

select count(*) from tab where idbdbroot(measure_id)=2 -- 691596700

select count(*) from tab where idbdbroot(measure_id)=3 -- 691596700

select count(*) from tab where idbdbroot(measure_id)=4 -- 691586700

However, he noticed that the table only "exists" on the MariaDB level on PM1. By this, he meant that SQLyog does not show that the tables exist on PM2-4, and that the .frm files don't exist in /usr/local/mariadb/columnstore/mysql/db/ on PM2-4.

I suspect that this is because PM1 is a "combined" UM/PM system, and PM2-4 are only PMs, and tables only "exist" at the MariaDB level on UMs. Is that correct? If so, then I think we should add a note that tables only "exist" in MariaDB on UMs to the following page:

https://mariadb.com/kb/en/library/columnstore-storage-architecture/

Currently, it says:

The MariaDB ColumnStore Table Schema when created are located in /usr/local/mariadb/columnstore/mysql/db with the other non-columnstore tables. The MariaDB ColumnStore data gets stored across the Performance Modules in dbroots, which are located in /usr/local/mariadb/columnstore/datax.

If it is true that the MariaDB schemas are only on UMs, then this line does not make that clear, so we should clarify that.

The users PM2-4 systems do have mysqld processes running. If the tables do not "exist" in MariaDB on PMs, then what does the mysqld process do on PMs? We should probably also make a note about that to the following page:

https://mariadb.com/kb/en/library/columnstore-performance-module/

Contrast this to the UM page, which does mention what the mysqld process does on UMs:

https://mariadb.com/kb/en/library/columnstore-user-module/