17.05 - EXPLAIN Request Modifier - Teradata Database

Teradata Vantage™ - Temporal Table Support

prodname
Advanced SQL Engine
Teradata Database
vrm_release
17.00
17.05
created_date
June 2020
category
Programming Reference
featnum
B035-1182-170K

You can use the EXPLAIN, STATIC EXPLAIN, and DYNAMIC EXPLAIN request modifiers to report temporal semantic operations. The explain text provides the type of qualifier applied on the temporal tables being operated upon. It reports whether the query is current, sequenced, or nonsequenced.

Here is an example of the EXPLAIN report for a current query on a row-partitioned bitemporal table:

EXPLAIN SELECT * FROM Policy;

Explanation
-----------------------------------------------------------------------
  1) First, we lock DBASE.Policy for read on a reserved RowHash
     in all partitions to prevent global deadlock for DBASE.Policy.
  2) Next, we lock DBASE.Policy for read.
  3) We do an all-AMPs RETRIEVE step from a single partition of
     DBASE.Policy  (with temporal qualifier as "CURRENT 
 VALIDTIME AND CURRENT TRANSACTIONTIME") with a condition of ( 
 "((BEGIN(DBASE.Policy.Validity ))<= DATE '2010-02-18') 
 AND (((END(DBASE.Policy.Policy_Duration ))= TIMESTAMP 
 '9999-12-31 23:59:59.999999+00:00') AND 
 ((END(DBASE.Policy.Validity ))> DATE '2010-02-18'))") 
     into Spool 1 (group_amps), which is built locally on the AMPs.
     The size of Spool 1 is estimated with no confidence to be 1 row (
     85 bytes).  The estimated time for this step is 0.03 seconds.
  4) Finally, we send out an END TRANSACTION step to all AMPs involved
     in processing the request.
  -> The contents of Spool 1 are sent back to the user as the result of
     statement 1.  The total estimated time is 0.03 seconds.