Range Buckets Registry entry

Define range buckets for a field (i.e. when fine-tuning Range Indexing).

EMu 4.0.01 introduced new tools that permit System Administrators to tune the range indexing used by EMu. Support for automatic optimisation of range indexes has also been added. Using these tools EMu can now provide optimal range indexes with significantly faster range based searches.

Range indexing is really a series of "mini" indexes on a per field basis. Unlike the Two Level scheme, where all search terms are placed in the one index, range terms are placed in per field indexes that are then concatenated to form one range index. Each field index consists of a number of range buckets. These buckets are used to indicate whether a given value falls within the bucket or not.

There are two related considerations when establishing range buckets:

  1. Data distribution: as best as possible data should be distributed evenly between the buckets.
  2. Logical query ranges. The aim is to minimise the necessity to check a bucket for a value as checking whether records in a bucket match the query takes time; therefore if users are likely to search on particular ranges (decades for instance: 1/1/1910 to 1/1/1920), it makes sense to configure range buckets appropriately.

The setting of range bucket values is performed on a per field basis. Each range indexed field may have a Registry entry that defines the range buckets for that field. If a Registry entry does not exist, the built-in values defined when the table was designed are used.

Note: See Range Indexing: EMu 4.0.01 onwards for details about EMu's range indexing tools, methods and theory,

The setting of range bucket values is performed on a per field basis. Each range indexed field may have a Registry entry that defines the range buckets for that field. If a Registry entry does not exist, the built-in values defined when the table was designed are used. Using the Range Buckets Registry entry, System Administrators can set the range buckets on any range based field manually.

Usage

This Registry entry is assigned at the system level only:

Key System
Key 1 System
Key 2 Setting
Key 3 Table
Key 4 table
Key 5 Range Buckets
Key 6 column
Value bucket;bucket;...
System Setting Table table Range Buckets column bucket;bucket;...

where:

table

is the name of the EMu module that contains the field to be configured.

column

is the name of the field (this can be determined by using the What's this help? facility in the EMu client, or via the emuindexing command).

bucket;bucket;...

is a semicolon separated list of values to be used for range buckets. The format of the value depends on the field type.

It is important to make sure that the values specified are all fully qualified. In particular, full date values are required. The table below shows what constitutes a fully qualified value for each field type:

Field Type

Format

Examples
Integer n -10, 12, 25
Float n.nnnn -23.0, -5, 2.125, 10
Date yyyy-mm-dd 2003-10-23, 2008-03-17
Time hh:mm:ss.sss 10:30:00, 18:00:00.000
Latitude dd:mm:ss.sss:D 9:12:15.1:N, 35:06:01:S
Longitude ddd:mm:ss.sss:D 123:34:06.34:W

Examples

In this example the Date Visited field has range buckets of 2000-01-01, 2003-01-01, 2006-01-01 and 2009-01-01. This entry may be used to set these buckets:

Field

Setting
Key 1 System
Key 2 Setting
Key 3 Table
Key 4 ecollectionevents
Key 5 Range Buckets
Key 6 ColDateVisited
Value 2000-01-01;2003-01-02;2006-01-01;2009-01-01

This Registry entry could be used to set the range buckets on the Latitude field in the Collection Events module:

Field

Setting
Key 1 System
Key 2 Setting
Key 3 Table
Key 4 ecollectionevents
Key 5 Range Buckets
Key 6 LatLatitude_tab
Value 16:00:00:S;18:00:00:S;20:00:00:S;22:00:00:S