17.05 - Example: Updating a Nonpartitioned Column with an Equality Constraint - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Manipulation Language

Product
Advanced SQL Engine
Teradata Database
Release Number
17.05
Release Date
January 2021
Content Type
Programming Reference
Publication ID
B035-1146-175K
Language
English (United States)

This example shows an update of a nonpartitioned column with an equality constraint on the partitioning column. With partition level locking, an all-AMP PartitionRange lock is used. The partition list contains a single partition pair.

The table definition for this example is as follows:

  CREATE TABLE HLSDS.SLPPIT1 (PI INT, PC INT, X INT, Y INT)
      PRIMARY INDEX (PI)
      PARTITION BY (RANGE_N(PC BETWEEN 1 AND 10 EACH 1));

An EXPLAIN of the UPDATE statement shows the partition lock:

  Explain UPDATE HLSDS.SLPPIT1 SET X = 3 WHERE PC = 10;
  1) First, we lock HLSDS.SLPPIT1 for write on a reserved rowHash in 
      a single partition to prevent global deadlock.
  2) Next, we lock HLSDS.SLPPIT1 for write on a single partition.
  3) We do an all-AMPs UPDATE from a single partition of HLSDS.SLPPIT1
      with a condition of ("HLSDS.SLPPIT1.PC = 10") with a residual
      condition of ("HLSDS.SLPPIT1.PC = 10").  The size is estimated
      with no confidence to be 1 row.  The estimated time for this 
      step is 0.05 seconds.
  4) Finally, we send out an END TRANSACTION step to all AMPs involved
      in processing the request.