Compute Expressions

You use compute expressions to calculate the value of a metric column based on mathematical or logical operations performed on other metric columns.

Compute expressions require at least one other metric column to be defined first, and can only include those metric columns that are listed before this metric column in order. You can use the up and down arrows to re-order metric columns. The value of the column is calculated using the given compute expression.

The following table shows operators which can be used while defining compute expression.

Operator	Example	Explanation
+	Column1 + Column2	Returns the sum of the values of Column1 and Column2.
-	(Column1 + Column2) - Column3	First add Column1 and Column2 values, then subtract Column3 value and return the result.
*	(Column1*Column2) + Column3	First multiply Column1 and Column2 values, then add Column3 value and return the result.
/	(Column1 + Column2) /2	Returns the average of Column1 and Column2 values.
__ceil	__ceil Column1	Returns the value of Column1 rounded off to the largest integer.
__floor	__floor Column1	Returns the value of Column1 rounded off to the lowest integer.
__round	__round Column1	This expression will round the value of Column1 to the nearest integer, away from zero.
==	Column1 == 1	Returns true if the value of Column1 is 1, else returns false.
!=	Column1 != 1	Returns false if the value of Column1 is 1, else returns true.
() ? : ;	(Status == 1) ? "UP": "DOWN"	This operator is equivalent to if then else statement. This expression will return "UP" if Status value is 1 otherwise it will return "DOWN"
__is_null	__is_null Column1	Returns true if the value of Column1 is NULL, else returns false.
__delta	__delta Column1	Returns the difference between the current value and the previous value of Column1.
__contains	Column1 __contains "ORA-"	Returns true if the value of Column1 contains the string "ORA-", else returns false.
__beginswith	Column1 __beginswith "ORA-"	Returns true if the value of Column1 starts with the string "ORA-", else returns false.
__matches	Column1 __matches "UP"	Returns true if the value of Column1 is equal to "UP", else returns false.
__length	__length Column1	Returns the length of string value of Column1.
__to_upper	__to_upper Column1	Returns the upper case of string value of Column1
__to_lower	__to_lower Column1	Returns the lower case of string value of Column1.
__interval	Column1 / __interval	Returns the Column1 value divided by the collection interval.

Refer to the examples for details about the expression grammar and usage.

Value	Definition
__interval	Collect interval.
__sysdate	Current system time.
__GMTdate	Current GMT time.
__contains	Tests a given string expression for presence of a string expression.
__beginswith	Tests whether a given string expression begins with a specified string expression.
__endswith	Tests whether a given string expression ends with the specified string expression.
__matches	Tests whether a given string expression matches a specified string expression.
__delta	Computes the difference between the current value and the previous value.
__leadingchars	Returns the leading characters in the specified string.
__trailingchars	Returns the trailing characters in the specified string.
__substringpos	Returns the position of the occurrence of the pattern within a specified string.
__is_null	Tests whether the expression is NULL
__length	Returns the length of the string expression.
__to_upper	Converts the string to upper case.
__to_lower	Converts the string to lowercase.
__ceil	Returns the smallest integral value not less than identifier.
__floor	Returns the largest integral value not greater than the identifier.
__round	Rounds to nearest integer, away from zero.

Examples:

• The value of the column is the average of the columns Column1 and Column2.

  NAME="Average" COMPUTE_EXPR="(Column1 + Column2 )/ 2" 

• The value of the column Version is computed as 7.X if column Column1 contains the String NetApp Release 7..

  NAME="Version" COMPUTE_EXPR="(Column1 __contains 'NetApp Release 7.') ? '7.X':'6.X'"

• The value of the column Column1 is the difference of the columns Column2 and Column3.

  NAME="Column1" COMPUTE_EXPR="(Column2 - Column3)"

• The value of the column Status is 1 if the value of column State matches the String STARTED and 0 otherwise.

  NAME="Status" COMPUTE_EXPR="State __matches 'STARTED'" 

• The value of the column Column1 is yes if the value of column Column2 is null and no otherwise.

  NAME="Column1" COMPUTE_EXPR="(__is_null Column2)?'yes':'no'" 

• The value of the column Source is lanplus if the length of string value of column result is 0; el e it is the value of the column result.

  NAME="Source" COMPUTE_EXPR="((__length result) == 0) ? 'lanplus' : result" 

• The value of the column Rate is the value of column Column1 divided by the collection interval, rounded up to the largest integer.

  NAME="Rate" COMPUTE_EXPR="(__ceil (Column1/__interval))"

• The value of the column is the Column1 when Column2 and Column3 are existing metric columns.

  NAME="Column1" COMPUTE_EXPR="((Column2 == 0) ? 0 : ((Column3 / (Column2 / 8)) * 100.0))"

• The value of the column is the total percentage of disk available where Column1 and Column2 are existing metric columns

  NAME="PERCENTAGE_VALUE" COMPUTE_EXPR="(Column1 != 0) ? 100.0*(Column2/Column1) : 0"