SEM_PERF.GATHER

Format

SEM_PERF.GATHER_STATS(
     just_on_values_table  IN BOOLEAN DEFAULT FALSE, 
     degree                IN NUMBER(38) DEFAULT NULL,
     estimate_percent      IN NUMBER DEFAULT DBMS_STATS.AUTO_SAMPLE_SIZE,
     value_method_opt      IN VARCHAR2 DEFAULT NULL,
     link_method_opt       IN VARCHAR2 DEFAULT NULL,
     network_owner         IN VARCHAR2 DEFAULT NULL,
     network_name          IN VARCHAR2 DEFAULT NULL);

Description

Gathers statistics about RDF and OWL tables and their indexes.

Parameters

just_on_values_table

TRUE collects statistics only on the table containing the lexical values of triples; FALSE (the default) collects statistics on all major tables related to the storage of RDF and OWL data.

A value of TRUE reduces the execution time for the procedure; and it may be sufficient if you need only to collect statistics on the values table (for example, if you use other interfaces to collect any other statistics that you might need).

degree

Degree of parallelism. For more information about parallel execution, see Oracle Database VLDB and Partitioning Guide.

estimate_percent

Determines the percentage of rows in RDF_LINK$ and RDF_VALUE$ to sample.

The valid range is between 0.000001 and 100. You can use the constant DBMS_STATS.AUTO_SAMPLE_SIZE (the default) to enable Oracle Database to determine the appropriate sample size for optimal statistics.

value_method_opt

Accepts either of the following options, or both in combination, for the RDF_VALUE$ table:

FOR ALL [INDEXED | HIDDEN] COLUMNS [size_clause]
FOR COLUMNS [size clause] column|attribute [size_clause] [,column|attribute [size_clause]...]

size_clause is defined as: size_clause := SIZE {integer | REPEAT | AUTO | SKEWONLY}

column is defined as: column := column_name | (extension)

integer : Number of histogram buckets. Must be in the range [1, 2048].
REPEAT : Collects histograms only on the columns that already have histograms.
AUTO : Oracle Database determines the columns to collect histograms based on data distribution and the workload of the columns.
SKEWONLY : Oracle Database determines the columns to collect histograms based on the data distribution of the columns.
column_name : name of a column
extension: Can be either a column group in the format of (column_name, column_name [, ...]) or an expression.

The usual default is: FOR ALL COLUMNS SIZE 2048

link_method_opt

Accepts either of the following options, or both in combination, for the RDF_LINK$ table:

FOR ALL [INDEXED | HIDDEN] COLUMNS [size_clause]
FOR COLUMNS [size clause] column|attribute [size_clause] [,column|attribute [size_clause]...]

size_clause is defined as: size_clause := SIZE {integer | REPEAT | AUTO | SKEWONLY}

column is defined as: column := column_name | (extension)

integer : Number of histogram buckets. Must be in the range [1,2048].
REPEAT : Collects histograms only on the columns that already have histograms.
AUTO : Oracle Database determines the columns to collect histograms based on data distribution and the workload of the columns.
SKEWONLY : Oracle Database determines the columns to collect histograms based on the data distribution of the columns.
column_name : Name of a column.
extension: Can be either a column group in the format of (column_name, column_name [, ...]) or an expression.

The usual default is: FOR ALL COLUMNS SIZE AUTO FOR COLUMNS SIZE 2048 P_VALUE_ID CANON_END_NODE_ID START_NODE_ID G_ID (CANON_END_NODE_ID, START_NODE_ID) (P_VALUE_ID, CANON_END_NODE_ID) (P_VALUE_ID, START_NODE_ID)

network_owner

Owner of the semantic network. (See Table 1-2.)

network_name

Name of the semantic network. (See Table 1-2.)

Usage Notes

To use this procedure, you must connect as a user with permission to execute it. Network owners and DBAs have privileges execute this procedure.

This procedure collects statistical information that can help you to improve inferencing performance, as explained in Enhancing Inference Performance. This procedure internally calls the DBMS_STATS.GATHER_TABLE_STATS procedure to collect statistics on RDF- and OWL-related tables and their indexes, and stores the statistics in the Oracle Database data dictionary. For information about using the DBMS_STATS package, see Oracle Database PL/SQL Packages and Types Reference.

Gathering statistics uses significant system resources, so execute this procedure when it cannot adversely affect essential applications and operations.

Examples

The following example gathers statistics about RDF and OWL related tables and their indexes.

EXECUTE SEM_PERF.GATHER_STATS(network_owner=>'RDFUSER', network_name=>'NET1');