Rule Definition
Whenever a query with a WHERE clause does not use the first column of composite index (multiple column base index), the database engine will not use the composite index to retrieve the data, potentially leading to very poor performance.

Remediation
Depending on the context, the user has to evaluate if the fact that the composite index is not is leading to poor performance. If the query does not use other indexes, the fact that the query does not use the first column of a composite index is most probably an error that needs to be fixed.

Violation Code Sample

The table T is defined the 4 following columns : A, B, C, D

The analyzed application  has one artifact that contains the following query : 
SELECT * FROM T WHERE B = 'X'

Example 1 : 
Table T has the following index defined i1 on (A, B, C) columns.
The artifact  will be part of the output of this metric to inform the user that i1 will not be used by the query processor engine. 

Example 2 : 
Table T has the following indexes defined  i2 (B, C) and i3 (B).
The artifact  will not  be part of the output of this metric (first column (i3)  or composite index( i2) is used).

Note  artifact  is part of the scope and is counted by the total procedure.

Example 3 : 
Table T has the following indexes defined  i1 (A, B, C), and i3 (B).
The artifact  will be part of the output of this metric to inform the user that i1 will not be used by the database engine, even if the database engine uses the index i3.

Example 4 :
Table T has the following index defined i3 (B).
The artifact  is ignored by this metric.