Projection Parameters
The following configuration parameters help you manage projections.
Query system table CONFIGURATION_PARAMETERS to determine what levels (node, session, database) are valid for a given parameter.
| Parameters | Description |
|---|---|
|
AnalyzeRowCountInterval |
Specifies how often Vertica checks the number of projection rows and whether the threshold set by For more information, see Collecting Database Statistics. Default: 86400 seconds (24 hours) |
| ARCCommitPercentage |
Sets the threshold percentage of WOS to ROS rows, which determines when to aggregate projection row counts and commit the result to the catalog. Vertica performs this action when the WOS to ROS percentage exceeds this setting. Default: 3 (percent) |
| ContainersPerProjectionLimit |
Specifies how many ROS containers Vertica creates per projection before ROS pushback occurs. Increasing this parameter's value can cause serious degradation of database performance. Vertica strongly recommends that you not modify this parameter without first consulting with Customer Support professionals. Default: 1024 |
| EnableGroupByProjections |
Specifies whether you can create live aggregate projections. For more information, see Live Aggregate Projections. Default: 1 (enable) |
| EnableExprsInProjections |
Specifies whether you can create projections that use expressions to calculate column values. For more information, see Aggregating Data Through Expressions. Default: 1 (enable) |
| EnableTopKProjections |
When set to Default: 1 (enable) |
|
MaxAutoSegColumns |
Specifies the number of columns (0 –1024) to use in an auto-projection's hash segmentation clause. Set to Default: 8 |
|
MaxAutoSortColumns |
Specifies the number of columns (0 –1024) to use in an auto-projection's sort expression. Set to Default: 8 |
| RebalanceQueryStorageContainers |
By default, prior to performing a rebalance, Vertica performs a system table query to compute the size of all projections involved in the rebalance task. This query enables Vertica to optimize the rebalance to most efficiently utilize available disk space. This query can, however, significantly increase the time required to perform the rebalance. By disabling the system table query, you can reduce the time required to perform the rebalance. If your nodes are low on disk space, disabling the query increases the chance that a node runs out of disk space. In that situation, the rebalance fails. Default: 1 (enable) |
|
SegmentAutoProjection |
Determines whether auto-projections are segmented if the table definition omits a segmentation clause. You can set this parameter at database and session scopes. Default: 1 (create segmented auto projections) |