Fail to Generate Prediction with Decision Tree Model after Upgrading MADlib to 1.12

Products

• VMware Tanzu Greenplum

Issue/Introduction

Symptoms:

After MADlib package is upgraded to version 1.12, it's getting errors when attempting to generate predictions with decision tree models that are trained prior to the upgrade.

Error Message:

ERROR: KeyError: 'null_proxy' (plpython.c:4656) 
CONTEXT: Traceback (most recent call last): 
PL/Python function "tree_predict", line 19, in <module> return decision_tree.tree_predict(**globals()) PL/Python function "tree_predict", 
line 1759, in tree_predict PL/Python function "tree_predict" ********** Error ********** ERROR: KeyError: 'null_proxy' (plpython.c:4656) SQL state: XX000 Context: Traceback (most recent call last): PL/Python function "tree_predict", 
line 19, in <module> return decision_tree.tree_predict(**globals()) PL/Python function "tree_predict", line 1759, in tree_predict PL/Python function "tree_predict"

Environment

Cause

The error is because the summary table in 1.12 contains a new entry called "null_proxy", which is expected in the predict function. However, the tables that are generated in older versions don't have such entry. 

 

Resolution

The issue has been identified as a defect and will be fixed in next release (v1.13). 

Before the fix is ready to apply, either of following options could be used as a workaround.

1. Add a column called "null_proxy" with "NULL" value in the summary table
2. Retrain the models which are trained on older versions (prior to 1.12)