This chapter describes Teradata Database primary indexe, primary AMP indexes, and no primary index objects..
The process of selecting a primary index is given heavy emphasis. Other topics describe unique versus nonunique, partitionin, primary index access to rows, the various performance considerations that pertain to primary indexes, special considerations for nonunique primary indexes relating to duplicate row checking, and space utilization parameters for primary indexes.
This chapter focuses on user data tables, but the considerations discussed for a base data table are largely identical to those for selecting a primary index, primary AMP index, or no primary index for a join index. Any join index-specific considerations are documented in Join and Hash Indexes.
This chapter also covers primary AMP indexes. Primary AMP (PA) index objects must be column partitioned (with or without row partitioning). A primary AMP index is a nonunique index. Row distribution to AMPs and which AMPs to access for a primary AMP index is the same as for a primary index. Accessing rows (or, more specifically, column partition values) on an AMP for a primary AMP index is the same as for a column-partitioned NoPI.
The chapter also covers tables and join indexes that neither have a primary index nor a primary AMP index. These database objects are referred to as NoPI objects.
NoPI objects come in two forms.
- Nonpartitioned NoPI objects
- Column-partitioned NoPI objects (with or without row partitioning)