Creating and Updating Structures for Thunderbolt Indexes

There are several methodologies for creating and updating structures for Thunderbolt Indexes. The available methodologies are:
      . The ddlStructure() function without the USING clause;
      . The ddlStructure() function without the USING clause and with the /C option;
      . The ddlStructure()/ddlStructureMem() function with the USING clause;
      . The ddlStructure()/ddlStructureMem() function with the USING clause and with the /C option;
      . The ddlConstruct() function;
      . The ddlUdiStruct() function;

The ddlStructure() function without the USING clause and without the /C option is the default methodology for building structures. All other methodologies are special cases. This form applies to all non-UDI index types.

In most cases (non-UDI), structures are updated automatically whenever records are modified or additional records are inserted. The exceptions are the LOAD/ddlLoad() functions; and optional forms of ddlCopyData() and ddlWrite(). The default form of the ddlStructure() functions will also perform incremental structure updates for these situations.

This form of the ddlStructure() functions build structures sequentially - i.e., one at a time.

The ddlStructure() function without the USING clause and with the /C option is optimized for low cardinality indexes. In this case, low is a relative term, meaning about 50,000 or less. For indexes that meet the constraint, this is a much faster way to build structures. In addition, this form can build multiple structures in parallel, as long as the combined cardinality meets the constraint.

The ddlStructure()/ddlStructureMem() functions with the USING clause are used for building initial structures for UDI index types such as virtual indexes and text search indexes.

The ddlStructure() function allows meta-data to be supplied in a Thunderbolt table or in a flat file. The ddlStructureMem() function allows meta-data to be supplied in a memory block.

UDI type indexes are not updated automatically when the underlying data is modified or when incremental records are added. When the underlying data is modified, it is necessary to use the ddlUdiStruct() function to update the corresponding indexes.

When incremental records are added, the respective structures can be updated by either means; STRUCTURE, ddlStructure()/ddlStructureMem() with USING clause; or ddlUdiStruct().

The ddlConstruct() function is an almost obsolete form. But it can be used in special circumstances such as very small incremental builds.

The ddlUdiStruct() function is used for updating structures for UDI index types.