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Support Article

Poor performance caused by SQL script



Performance problem within Oracle SQL alerts were found in log. The problem appears in Select against a custom work item table, where a pzInsKey reference was imposed in the Where clause of the Select.

Error Messages

Not Applicable

Steps to Reproduce

There is no specific use case to replicate the issue.

Root Cause

The following Select was issued against the database:

select pzPVStream from XXX_YYYNotifications where pzInsKey = ?

The first 32 characters of All instances of this property contained a common string value:


Due to this non-uniqueness, the Oracle Optimizer rejected the use of any existing Indexes on this table or property, and will resort to full table scans to resolve the SQL.


Perform the following local-change:

1. Delete the Histogram Data on XXX_YYYNOTIFICATIONS table and PZINSKEY property. 

2. Configure the database to not compute Histogram data for this property during future Compute or Estimate table statistics. 

3. Trigger a regeneration of index data on the table.

4. Tune Oracle to use Indexes rather than performing a Full Table Scan.

Published March 17, 2016 - Updated October 8, 2020

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