file handle count calculation
I have been struggling to find a relation between Open file handle count and Vertica process on each node.
How can we determine, how many files does vertica open for a query.
I know we can use resource acquisitions table, but I need to understand the logic behind these numbers.
A ROS container can have many files, one file for each column of that container.
If a select query with only one column is executed, then it should open only the index file and file containing the column values in that ROs container as a result of partition pruning, but this is not observed in simple cases.
I tried querying the single column of a partitioned table with 20 values. The data was distributed on all nodes of a 3 node cluster, but the query shows file handle count as
Node 1 : 7 (initiator)
Node 2 : 4
Node 3 : 4
I query two columns and the result changes
Node 1 : 9 (initiator)
Node 2 : 6
Node 3 : 6
Any expalnation to logic would be appreciated.