Specifies the percent of space on each HG garray page to reserve for future incremental inserts into existing groups.
Option can be set at the database (PUBLIC) or user level. When set at the database level, the value becomes the default for any new user, but has no impact on existing users. When set at the user level, overrides the PUBLIC value for that user only. No system privilege is required to set option for self. System privilege is required to set at database level or at user level for any user other than self.
Requires the SET ANY PUBLIC OPTION system privilege to set this option. Can be set temporary for an individual connection or for the PUBLIC role. Takes effect immediately.
The garray tries to pad out each group to include a pad of empty space set by the value. This space is used for rows added to existing index groups.
An HG index can reserve some storage on a per-group basis (where group is defined as a group of rows with equivalent values). Reserving space consumes additional disk space, but can help the performance of incremental inserts into the HG index.
If you plan to do future incremental inserts into an HG index, and those new rows have values that are already present in the index, a nonzero value for this option might improve incremental insert performance.
If you do not plan to incrementally update the index, you can reduce the values of this option to save disk space.