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

SQL Data Manipulation Language

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Published
July 2021
Language
English (United States)
Last Update
2021-07-27
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B035-1146
lifecycle
previous
Product Category
Teradata Vantageā„¢

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.