Skip to end of metadata
Go to start of metadata

Use

 <number of> <optimizer_strategy_executes>, selectivity <percentage>%: <number of> rows read, <number of> rows qualified

Explanation

The ratio of read table rows to found table rows is poor when a particular access strategy (<optimizer_strategy_executes>) is used.

The access strategy can be one of the following strategies:

  • Primary key accesses( EQUAL CONDITION FOR KEY, SUBQ CONDITION FOR KEY, IN CONDITION FOR KEY)
  • Primary key range accesses (RANGE CONDITION FOR KEY, SUBQ CONDITION FOR KEY, IN CONDITION FOR KEY)
  • Index accesses( EQUAL CONDITION FOR INDEX, SUBQ CONDITION FOR INDEX, IN CONDITION FOR INDEX)
  • Index range accesses( RANGE CONDITION FOR INDEX, SUBQ CONDITION FOR INDEX, IN CONDITION FOR INDEX)
  • Isolated index accesses see : EXPLAIN statement: Columns O,D,T,M, column O ( Only Index) as well as Index accesses
  • Isolated index range accesses see : EXPLAIN statement: Columns O,D,T,M, column O ( Only Index) as well as Index range accesses
  • Isolated index scans( INDEX SCAN ) 


User Response

Find the statement that causes this poor ratio of read rows to found rows, and check the access strategies for this statement.

Note:

For information on creating optimized SQL statements, see the SQL Optimizer documentation. See also: TABLE SCAN

 

More Information

Relevant  DB-Analyzer Files
Helpful with ...
DBAN_STRATEGY_INDEX.csvAccesses and selectivity for index searches
DBAN_STRATEGY_PRIMKEY.csvAccesses and selectivity for PRIMARY KEY searches
DBAN_STRATEGY_SCANS.csv Accesses and selectivity for INDEX SCAN and TABLE SCAN searches 
SAP Note
Helpful with ...
  
Expert Sessions (Link to trainings)
Content / Helpful with ...

Session 16: SAP MaxDB SQL Query Optimization (Part 1)
Session 16: SAP MaxDB SQL Query Optimization (Part 2)

Find detailed information about different optimizer strategies and performance optimization.
Documentation (links)
Helpful with ...
SQL Optimizer <übernommen>
SQL Opimizer
List of All Search Strategies
 
SQL Opimizer
Displaying the Search Strategies Used by SQL Statements (EXPLAIN)
 
  • No labels