Github user njayaram2 commented on a diff in the pull request:
https://github.com/apache/incubator-madlib/pull/44#discussion_r65457433
--- 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
--- End diff --
Are you suggesting we mandate that the input table has no NULL timestamps?
I tried leaving out the NOT NULL mentioned in the comment, but it will end
up showing a session id for rows with NULL timestamps too if I do that. I
wanted to make sure rows with NULL timestamps have no session ID at all, so had
included the NOT NULL along with the NOT NULL inside the subselect.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
