@Override
  public long ramBytesUsed() {
    return INSTANCE_SIZE
        + RamUsageEstimator.sizeOf(functionName)
        + RamUsageEstimator.sizeOf(parametersString)
        + RamUsageEstimator.sizeOfMap(functionAttributes)
        + (expressions == null
            ? 0
            : expressions.stream()
                .mapToLong(MemoryEstimationHelper::getEstimatedSizeOfAccountableObject)
                .sum())
        + (paths == null
            ? 0
            : paths.stream().mapToLong(MemoryEstimationHelper::getEstimatedSizeOfPartialPath).sum())
        + (countTimeExpressions == null
            ? 0
            : countTimeExpressions.stream()
                .mapToLong(MemoryEstimationHelper::getEstimatedSizeOfAccountableObject)
                .sum());
  }
Generates the parameter part of the function column name.

<p>Example:

<p>Full column name -> udf(root.sg.d.s1, sin(root.sg.d.s1), 'key1'='value1', 'key2'='value2')

<p>The parameter part -> root.sg.d.s1, sin(root.sg.d.s1), 'key1'='value1', 'key2'='value2'
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/expression/multi/FunctionExpression.java