7.00.02 - Deleting Duplicate Edges Table Rows - Aster Analytics

Teradata Aster® Analytics Foundation User GuideUpdate 2

Product
Aster Analytics
Release Number
7.00.02
Release Date
September 2017
Content Type
Programming Reference
User Guide
Publication ID
B700-1022-700K
Language
English (United States)

The edges table of an undirected graph can have duplicate rows, because each edge between vertices A and B is represented by two rows—one row has A in the source column and B in the target column, and the other row has B in the source column and A in the target column. Teradata recommends deleting duplicate rows from the edges table, using this code (where edges_table is the edges table name):

DROP TABLE IF EXISTS copy;

CREATE TABLE copy DISTRIBUTE BY HASH(source)
  AS SELECT *, ROW_NUMBER() OVER(ORDER BY source, target) rn
    FROM edges_table;

DROP TABLE IF EXISTS DuplicatesRemoved;

CREATE TABLE DuplicatesRemoved AS * SELECT FROM copy;

DELETE FROM DuplicatesRemoved WHERE rn IN (
  SELECT a.rn FROM DuplicatesRemoved a
  JOIN Copy b
  ON a.source=b.target AND a.target=b.source AND a.rn < b.rn);

DROP TABLE IF EXISTS Copy;
AllPairsShortestPath DuplicatesRemoved Table Schema
Column Name Data Type Description
source VARCHAR Source key.
target VARCHAR Target key.
rn INTEGER Row number in edges_table.