[OAK-2315] Index cost is sometimes negative (index type "property")

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.0.9, 1.1.3
• Component/s: core, query
• Assignee: Thomas Mueller
• Reporter: Thomas Mueller
• Created: 03/Dec/14 07:49
• Updated: 08/Feb/17 10:06
• Resolved: 03/Dec/14 10:39

Description

The property index can return a negative cost in the following case:

• It is a non-unique index (the default)
• The "entryCount" is set to lower than 10000
• The "keyCount" property is not set, or set to 0
• The index matches

In this case, the following formula is used and returns a negative value:

(long) ((double) count / keyCount) + size;

Count is for example 500, keyCount is 0. The division evaluates to infinity, which is converted to Long.MAX_VALUE. Size is larger than 0, so there is an overflow to negative.