multiply (Compute)

When To Use

Use multiply to multiply every value of one column by an operand, row by row. The operand is either a literal number or, with the $n syntax, the value of another column of the same row. It is the workhorse of unit conversion — kilobytes to bytes (value: 1024), megabytes to bytes (value: 1048576), ratios to percentages (value: 100) — and value: -1 negates a column when you need to compute constant - column together with add. The column values must be numeric.

Syntax

sources:
  memoryUsage:
    type: wmi
    namespace: root\CIMv2
    query: SELECT FreePhysicalMemory,TotalVisibleMemorySize FROM Win32_OperatingSystem
    computes:
    # Convert kilobytes to bytes
    - type: multiply
      column: 1
      value: 1024
    - type: multiply
      column: 2
      value: 1024

Properties

Table Transformation Example

With column: 1 and value: 1024, then column: 2 and value: 1024:

Recommended Pattern

• Convert source units to the units expected by the metric right after collection, and record the conversion in a comment (# Convert kilobytes to bytes).
• Use value: -1 followed by add when you need constant - column (e.g. endurance remaining = 100 - wear), since subtract only computes column - value.
• When the same conversion applies to several columns, chain one multiply per column in the same computes list rather than post-processing in the mapping.

Common Mistakes

• Converting units twice: check whether the mapping already applies a conversion function (e.g. megaHertz2Hertz, percent2Ratio) before also multiplying in the compute pipeline.
• Using the wrong factor for byte conversions (1024 for kB, 1048576 for MB — not 1000).
• Applying multiply to a column that contains non-numeric text such as an empty string or a label.

Community Examples

• GenericUPS^[1]
• Windows^[2]
• WinStorageSpaces^[3]

From WinStorageSpaces.yaml, computing 100 - Wear with a negation followed by an addition, included directly from the connector source:

  # Convert Wear into EnduranceRemaining (Endurance Remaining = 100 - Wear)
  # DeviceId;TotalErrors;EnduranceRemaining;WriteErrors;
- type: multiply
  column: 3
  value: -1
- type: add
  column: 3
  value: 100