About Server Configuration Parameters

There are many HAWQ server configuration parameters that affect the behavior of the HAWQ system. Many of these configuration parameters have the same names, settings, and behaviors as in a regular PostgreSQL database system.

• Parameter Types and Values describes the parameter data types and values.
• Setting Parameters describes limitations on who can change them and where or when they can be set.
• Configuration Parameter Categories organizes parameters by functionality.
• Configuration Parameters lists the parameter descriptions in alphabetic order.

Parameter Types and Values

All parameter names are case-insensitive. Every parameter takes a value of one of four types: Boolean, integer, floating point, or string. Boolean values may be written as ON, OFF, TRUE, FALSE, YES, NO, 1, 0 (all case-insensitive).

Some settings specify a memory size or time value. Each of these has an implicit unit, which is either kilobytes, blocks (typically eight kilobytes), milliseconds, seconds, or minutes. Valid memory size units are kB (kilobytes), MB (megabytes), and GB (gigabytes). Valid time units are ms (milliseconds), s (seconds), min (minutes), h (hours), and d (days). Note that the multiplier for memory units is 1024, not 1000. A valid time expression contains a number and a unit. When specifying a memory or time unit using the SET command, enclose the value in quotes. For example:

SET hawq_rm_stmt_vseg_memory TO '4GB';

Note: There is no space between the value and the unit names.

Setting Parameters

Many of the configuration parameters have limitations on who can change them and where or when they can be set. For example, to change certain parameters, you must be a HAWQ superuser. Other parameters require a restart of the system for the changes to take effect. A parameter that is classified as session can be set at the system level (in the hawq-site.xml file), at the database-level (using ALTER DATABASE), at the role-level (using ALTER ROLE), or at the session-level (using SET). System parameters can only be set by using the hawq config utility or by directly modifying a hawq-site.xml file.

By design, all HAWQ instances (including master and segments) host identical hawq-site.xml files. Using a common hawq-site.xml file across all HAWQ instances simplifies configuration of the cluster. Within each hawq-site.xml configuration file, some parameters are considered segment parameters, meaning that each segment instance looks to its own hawq-site.xml file to get the value of that parameter. By convention, these parameter names begin with the string hawq_segment. Others parameters are considered master parameters. By convention, these parameter names begin with the string hawq_master. Master parameters are only applied at the master instance and ignored by segments.

Note: If you use the hawq config utility to set configuration parameter values in hawq-site.xml, the utility synchronizes all configuration files. Any manual modifications that you made to individual hawq-site.xml files may be lost. Additionally, if you install and manage HAWQ using Ambari, do not use hawq config to configure HAWQ properties. If the cluster is restarted, Ambari will overwrite any changes made by hawq config For Ambari-managed HAWQ clusters, only use the Ambari administration interface to set or change HAWQ configuration properties.

This table describes the values in the Set Classifications column of the table in the description of a server configuration parameter.