5.4 Filter Expressions

The video tutorial Record Filters and Tabs on Youtube will explain  how to use record filters and tabs.

Filter expressions specify what log records should be processed by an analyze function or a category of analyze functions. A filter expression has its own node in the Functions tree. Filter expressions can be sub-nodes of analyze functions or of categories. In order to assign a filter expression to an analyze function or a category you have to make it a sub-node of the analyze function respectively of the category. If a filter expression is a sub-node of a category it is applied to all analyze functions that belong to this category.

You might think that filter expressions are only used by records filters but they are used by all analyze functions and not only by record filters, e.g. graphs use filter expressions to determine what log records should be displayed. Filter expressions are Boolean expressions, i.e. the expression is either true or false. If Ascolog Insight has to apply an analyze function it evaluates for each log record if the filter expression is true or false. If it is false the log record is ignored (filtered out), otherwise the log record is processed. When you press the CTRL key while creating a filter expression a logical NOT will be applied to the filter expression.