[GitHub] incubator-madlib pull request #44: Feature: Sessionize funtion

[decibel <gi...@git.apache.org>]

Github user decibel commented on a diff in the pull request:

    https://github.com/apache/incubator-madlib/pull/44#discussion_r65424347
  
    --- 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 --
    
    Is it necessary to include rows with NULL timestamps? While that's not a big deal here, I think it's going to lead to unwanted complexity down the road (I'm looking at JIRA MADLIB-1002).


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