Github user decibel commented on a diff in the pull request:
https://github.com/apache/incubator-madlib/pull/44#discussion_r65437304
--- Diff: src/ports/postgres/modules/utilities/sessionize.py_in ---
@@ -0,0 +1,101 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+import plpy
+import string
+
+from control import MinWarning
+from utilities import unique_string, _assert
+from validate_args import get_cols
+from validate_args import input_tbl_valid, output_tbl_valid, is_var_valid
+
+m4_changequote(`<!', `!>')
+
+def sessionize(schema_madlib, source_table, output_table, partition_expr,
+ time_stamp, time_out, **kwargs):
+ """
+ Perform sessionization over a sequence of rows.
+
+ Args:
+ @param schema_madlib: str, Name of the MADlib schema
+ @param source_table: str, Name of the input table/view
+ @param output_table: str, Name of the table to store result
+ @param partition_expr: str, Expression to partition (group) the
input data
+ @param time_stamp: float, Column name with time used for
sessionization calculation
+ @param time_out: float, Delta time between subsequent events to
define a sessions
+
+ """
+ with MinWarning("error"):
+ _validate(source_table, output_table, partition_expr,
time_stamp, time_out)
+
+ all_input_cols_str = ', '.join([i.strip() for i in
get_cols(source_table, schema_madlib)])
+ session_id = 'session_id' if not is_var_valid(source_table,
'session_id') else unique_string('session_id')
+
+ plpy.execute("""
+ CREATE TABLE {output_table} AS
+ SELECT
+ {all_input_cols_str},
+ CASE WHEN {time_stamp} NOTNULL
+ THEN (SUM(new_event_boundary)
OVER (PARTITION BY {partition_expr} ORDER BY {time_stamp})) END AS {session_id}
--- End diff --
I did some refactoring of this while taking a look at
https://issues.apache.org/jira/browse/MADLIB-1002. Please take a look at it, as
I think it's clearer than this code. *Note that I have not tested it for
correctness!*
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