Bulk Extract

The bulk extract feature allows all the data from a particular table or tables to be extracted directly from the Smallworld GIS without the use of a spatial scanner. The bulk extract feature provides a faster method of carrying out large, one off, data extracts and may be performed on either geographic or non-geographic data.

A request for a bulk extract is made using the SwERVE Management Console. The bulk extract process is illustrated in Figure 4

Figure 4 Bulk Extract

Differential Bulk Extract

The differential bulk extract feature is similar to the bulk extract in so far as it allows data from tables to be extracted directly from the Smallworld GIS without the use of a spatial scanner.

It differs from the bulk extract in that it only extracts data from tables that have changed since a full bulk extract or a check-pointed differential bulk extract has been carried out.

Bulk checkpoints are created in whatever alternative the SwERVE Server is running. Unique checkpoints are created for each table being extracted and are named [Collection_Code]_[Table_Code]_Bulk or [Collection_Code]_[Table_Code]_Check depending on which mode of bulk extract is being used. Collection_Code and Table_Code are system-generated codes representing the collection name and table name. The state of the data for a particular table at the time of the bulk or check-pointed bulk extract is represented by this checkpoint.

A request for a differential bulk extract is made using the SwERVE Management Console.

Cache Extract

A cache extract is similar to a bulk extract but additionally it employs a checkpoint within the GIS to determine what changes have occurred since the extract was performed. Data caching is provided as a means of improving the performance of a spatial extract. Typically this is used where a particular data type is frequently extracted. In this, a combination of pre-extracted (cached) and changed data is used. Cached data is stored in a shared folder.

Cache checkpoints are created in whatever alternative the SwERVE Server is running. Unique checkpoints are created for each table being cached and are named _SwERVE_Cache_[Dataset_Code]_[Table_Code] where Dataset_Code and Table_Code are system-generated codes representing the table name. The state of the data cached for a particular table is represented by this checkpoint. Data may be cached for any number of tables.

A request to cache data from a particular table is made using the Swerve Management Console. The Cache Extract Process is illustrated in Figure 5.

Figure 5 Cache Extract