OPG_APIS.PR

Format

OPG_APIS.PR(
     edge_tab_name   IN VARCHAR2,
     d               IN NUMBER DEFAULT 0.85,
     num_iterations  IN NUMBER DEFAULT 10,
     convergence     IN NUMBER DEFAULT 0.1,
     dop             IN INTEGER DEFAULT 4,
     wt_node_pr      IN OUT VARCHAR2,
     wt_node_nextpr  IN OUT VARCHAR2,
     wt_edge_tab_deg IN OUT VARCHAR2,
     wt_delta        IN OUT VARCHAR2,
     tablespace      IN VARCHAR2 DEFAULT NULL,
     options         IN VARCHAR2 DEFAULT NULL,
     num_vertices    OUT NUMBER);

Description

Prepares for page rank calculations.

Parameters

edge_tab_name

Name of the property graph edge table.

d

Damping factor.

num_iterations

Number of iterations for calculating the page rank values.

convergence

A threshold. If the difference between the page rank value of the current iteration and next iteration is lower than this threshold, then computation stops.

dop

Degree od parallelism for the operation.

wt_node_pr

Name of the working table to hold the page rank values of the vertices.

wt_node_pr

Name of the working table to hold the page rank values of the vertices.

wt_node_next_pr

Name of the working table to hold the page rank values of the vertices in the next iteration.

wt_edge_tab_deg

Name of the working table to hold edges and node degree information.

wt_delta

Name of the working table to hold information about some special vertices.

tablespace

Name of the tablespace to hold all the graph data and index data.

options

Additional settings for the operation. An optional string with one or more (comma-separated) of the following values:

CREATE_UNDIRECTED=T
REUSE_UNDIRECTED_TAB=T

num_vertices

Number of vertices processed by the page rank calculation.

Usage Notes

The property graph edge table must exist in the database, and the OPG_APIS.PR_PREP procedure must have been called.

Examples

The following example performs preparation, and then calculates the page rank value of vertices in a property graph named mypg.

set serveroutput on
DECLARE
    wt_pr  varchar2(2000); -- name of the table to hold PR value of the current iteration
    wt_npr varchar2(2000); -- name of the table to hold PR value for the next iteration
    wt3    varchar2(2000); 
    wt4    varchar2(2000); 
    wt5    varchar2(2000); 
    n_vertices number;
BEGIN
    wt_pr := 'mypgPR';
    opg_apis.pr_prep('mypgGE$', wt_pr, wt_npr, wt3, wt4, null);
    dbms_output.put_line('Working table names  ' || wt_pr 
       || ', wt_npr ' || wt_npr || ', wt3 ' || wt3 || ', wt4 '|| wt4);
    opg_apis.pr('mypgGE$', 0.85, 10, 0.01, 4, wt_pr, wt_npr, wt3, wt4, 'SYSAUX', null, n_vertices)
;
END;
/

The output will be similar to the following.

Working table names  "MYPGPR", wt_npr "MYPGGE$$TWPRX277", wt3
"MYPGGE$$TWPRE277", wt4 "MYPGGE$$TWPRD277"

The calculated page rank value is stored in the mypgpr table which has the following definition and data.

SQL> desc mypgpr;
 Name					   Null?    Type
 ----------------------------------------- -------- ----------------------------
 NODE					   NOT NULL NUMBER
 PR						            NUMBER
 C						              NUMBER

SQL> select node, pr from mypgpr;

      NODE	   PR
---------- ----------
       101	.1925
       201	.2775
       102	.1925
       104  .74383125
       105  .313625
       103	.1925
       100	.15
       200	.15