In
order to speed up data processing for objects leveraging HANA
Smart Data Access (SDA) there need to be a database statistics build. It is
a concept known in many databases. Once the table is indexed, no of records is known,
meta data is described etc. the processing of that table is much faster. It is valid for tables consumed in SAP HANA or
SAP BW based on SDA.
As the SDA doesn’t store the data in HANA DB persistently it uses virtual
tables instead also those can be indexed in order to run the SQL statements in efficient
manner – so called efficient query plan.
In
SAP BW there is an ABAP program called RSSDA_CREATE_TABLE_STAT
to be used to create database statistics for HANA Virtual Tables. BW’s objects
like InfoProviders (aDSO and Open ODS Views) and DataSources are supported by
the report. There are three types if the DB statistics that can be generated by
the program:
1. Record
Count – very basic one, providing only no of records
2. Simple - basic
statistics like min, max, null count, count, and distinct count
3. Histogram –
most detailed type, it estimates a data distribution in a single-column data
source
To
incorporate the DB statistics creation for SDA based data sources in BW use
ABAP process type in process chains.
Higher versions of BW 7.5
even have a new process type (SSDA_CREATE_TABLE_STAT under category 'Other') available
for including the creation of statistics in BW Process Chains.
More
information:
1990181 - BW HANA
SDA: Create Database Statistics for Virtual Tables of Open ODS Views and
Near-Line Storage (NLS) Archives
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