Github user njayaram2 commented on a diff in the pull request:
https://github.com/apache/incubator-madlib/pull/112#discussion_r111456660
--- Diff: src/ports/postgres/modules/graph/pagerank.py_in ---
@@ -158,44 +313,198 @@ def pagerank(schema_madlib, vertex_table, vertex_id,
edge_table, edge_args,
# https://en.wikipedia.org/wiki/PageRank#Damping_factor
# The query below computes the PageRank of each node using the
above formula.
+ # A small explanatory note on ignore_group_clause:
+ # This is used only when grouping is set. This essentially will
have
+ # the condition that will help skip the PageRank computation on
groups
+ # that have converged.
plpy.execute("""
CREATE TABLE {message} AS
- SELECT {edge_temp_table}.{dest} AS {vertex_id},
-
SUM({v1}.pagerank/{out_cnts}.{out_cnts_cnt})*{damping_factor}+{random_prob} AS
pagerank
+ SELECT {grouping_cols_select} {edge_temp_table}.{dest} AS
{vertex_id},
+
SUM({v1}.pagerank/{out_cnts}.{out_cnts_cnt})*{damping_factor}+{random_jump_prob}
AS pagerank
FROM {edge_temp_table}
- INNER JOIN {cur} ON
{edge_temp_table}.{dest}={cur}.{vertex_id}
- INNER JOIN {out_cnts} ON
{out_cnts}.{vertex_id}={edge_temp_table}.{src}
- INNER JOIN {cur} AS {v1} ON
{v1}.{vertex_id}={edge_temp_table}.{src}
- GROUP BY {edge_temp_table}.{dest}
- """.format(**locals()))
+ INNER JOIN {cur} ON {cur_join_clause}
+ INNER JOIN {out_cnts} ON {out_cnts_join_clause}
+ INNER JOIN {cur} AS {v1} ON {v1_join_clause}
+ {vertices_per_group_inner_join}
+ {ignore_group_clause}
+ GROUP BY {grouping_cols_select} {edge_temp_table}.{dest}
+ """.format(grouping_cols_select=edge_grouping_cols_select+', '
+ if grouping_cols else '',
+
random_jump_prob='MIN({vpg}.{random_prob})'.format(**locals())
+ if grouping_cols else random_probability,
+ vertices_per_group_inner_join="""INNER JOIN
{vertices_per_group}
+ AS {vpg} ON {vpg_join_clause}""".format(**locals())
+ if grouping_cols else '',
+ ignore_group_clause=' WHERE '+get_ignore_groups(
+ summary_table, edge_temp_table, grouping_cols_list)
+ if iteration_num>0 and grouping_cols else '',
+ **locals()))
# If there are nodes that have no incoming edges, they are not
captured in the message table.
# Insert entries for such nodes, with random_prob.
plpy.execute("""
INSERT INTO {message}
- SELECT {vertex_id}, {random_prob}::DOUBLE PRECISION AS
pagerank
- FROM {cur}
- WHERE {vertex_id} NOT IN (
+ SELECT {grouping_cols_select} {cur}.{vertex_id},
{random_jump_prob} AS pagerank
+ FROM {cur} {vpg_from_clause}
+ WHERE {vpg_where_clause} {vertex_id} NOT IN (
--- End diff --
The query does takes care of the scenario you mentioned. The
`{message_grp_where}` clause inside NOT IN checks if
`cur.grouping_cols=message.grouping_cols`. I also tried an example to confirm
it does work as expected. So leaving this as is.
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