HANA Code Remediation
Navneet
July 8, 2015
HANA Code Remediation Guidelines
HANA developments guidelines are an outcome of HANA migration projects as well as continuous code improvements.
How-to-Guide address statements creating a high workload on HANA DB and therefore should be avoided during
development phase.
Each solution/product architect and developer are responsible to apply these guides in order to keep HANA DB
performance stable over the time.
Analysis of WHERE Condition for SELECT
Changing database access in loops
Database Hints
Native SQL
Search problematic SELECT statements
Search SELECT .. FOR ALL ENTRIES-clauses
How to Search SELECT for Pool- or Cluster-Tables without ORDER BY
How to Table Attributes Check
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
2
HANA Code Remediation Guidelines
Analysis of WHERE Condition For SELECT
Problem
A SELECT statement without a WHERE condition reads the entire table.
Solution
Check whether the data selection can be limited through use of a suitable WHERE condition.
False-Positive can be suppressed using the pseudo comment "#EC CI_NOWHERE
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
3
HANA Code Remediation Guidelines
Changing database access in loops
Problem
Changing database statements like INSERT, UPDATE, MODIFY, DELETE in loops lead to multiple database accesses. Loops could be:
• SELECT ... ENDSELECT.
• LOOP ... ENDLOOP.
• DO ... ENDDO.
• WHILE ... ENDWHILE.
• PROVIDE ... ENDPROVIDE.
Solution
Check whether an array change is possible.
False-Positive can be hidden by using the pseudo comment "#EC CI_IMUD_NESTED.
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
4
HANA Code Remediation Guidelines
Database Hints
Problem
•
Hints can only be evaluated at runtime and they cannot be checked with ABAP syntax analysis. Incorrect entries can cause a runtime
error. Invalid hints may also be ignored, depending on the database.
•
hints are specific for one system configuration and its quantity structure.
•
A hint does not have any functional effects in this case. This means that although it influences the process duration, it does not
influence the resulting set of a statement. For this reason you cannot usually check in the program if a hint was ever evaluated.
Solution
Do not use hints for databases that are not listed in SAP note 129385 "Database hints in Open SQL".
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
5
HANA Code Remediation Guidelines
Native SQL
Problem
•
Programs with Native SQL statements are generally dependent on the database system used, so that they cannot be executed in all
AS ABAP systems.
•
Native SQL statements are not checked completely by the syntax check
Solution
Do not use Native SQL. It is recommended to use the Open SQL subset in SAP standard.
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
6
HANA Code Remediation Guidelines
Search Problematic SELECT * Statements
Problem
In general a SELECT * statement lead to performance & memory issues. due to the HANA column based storage of tables the select * is
not recommended. If not all table fields are used the select should be limited to the fields which are required.
Solution
•
Do not select more fields than required! However, it has to be ensured that all required fields are read.
•
If the SELECT is only used for existence check use addition UPTO 1 ROWS or SELECT SINGLE
NOTE - A correction for existing code is only recommended for tables with more than 50 fields by standard development. For less than
50 fields an adaption is only recommended if more than 1000 records are read.
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
7
HANA Code Remediation Guidelines
SELECT… FOR ALL ENTRIES clause
Problem
In case the internal table is empty the content of the database table would be read completely.
The addition FOR ALL ENTRIES ignores SAP buffering for:
•
Tables with single record buffering,
•
Tables with generic buffering if the condition after FOR ALL ENTRIES prevents precisely one generic area from being specified
exactly
Solution
It is always a good idea to perform some performance tests comparing FOR ALL ENTRIES and INNER JOIN ... to identify the best and
fastest solution.
It is best practice to check SELECT ... FOR ALL ENTRIES with an explicit test for content. For e.g. by using an IF statement.
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
8
HANA Code Remediation Guidelines
SELECT for POOL or CLUSTER tables without ORDER BY
Problem
Cluster Tables and pool tables has been migrated to transparent tables (Few Pool Tables still exist). But the data selection is not sorted
automatically by using the normal Select statement.
Solution
Select without an ORDER BY clause on pool or cluster tables must be checked if an explicit ORDER BY clause is necessary:
•
If the order of records is relevant add an ORDER BY clause.
•
If the order of records does not matter suppress the message via the pseudo comment
"#EC CI_NOORDER
Notes
•
SELECT SINGLE statements are not analyzed since they retrieve only one line and sorting is therefore not relevant.
•
If the result of the SELECT statement is moved into a sorted internal table, a special message is raised.
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
9
HANA Code Remediation Guidelines
TABLE Attribute Check
Problem
The HANA database does not use classical table buffering methods. Each read goes to the live data. Therefore Non-buffered tables
need to be checked if buffering needs to be enabled on application server side.
Solution
The solution depends on the table content. The technical settings (transport attributes, buffering) and the secondary indices of the
database table have to be checked and if necessary to be maintained.
In general tables can be buffered if:
•
They can be buffered 'logically'.
•
They are not too big.
•
Most of the accesses are reads, low amount of writes.
•
Way how they are accessed fits to the buffering technique
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
10
Code Inspector Checks – Part I
For HANA Code remediation activity, Code inspector variants “FUNCTIONAL_DB” and
“FUNCTIONAL_DB_ADDITION”.
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
11
Code Inspector Checks – Part II
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
12
Code Inspector Checks – Part III
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
13
Code Inspector Checks – Part IV
© 2015 SAP SE or an SAP affiliate company. All rights reserved.
14
Thank you
Navneet Chaubey
© 2015 SAP SE or an SAP affiliate company. All rights reserved.