Accomplish most common querying tasks using a set of simple queries
available in the Visual editor: filter, aggregate, join, compute, union, and
pattern.
The tools for these six queries are available as objects in
the Palette, in Streams and Windows.
Filter – allows you to filter a stream down to only the events of
interest, based on a filter expression.
Similar
to SQL WHERE clause.
Aggregate – allows you to group events that have common values and
compute summary statistics for the group, such as an average. You can also
define a window size, based on either time or number of events.
Uses
the CCL GROUP BY clause, similar to SQL GROUP BY.
Join – allows you to combine records from multiple streams or
windows, forming a new record with information from each source.
Comparable
to a join in SQL, where you specify two or more sources in the FROM
clause.
Compute – allows you to create a new
event
with a different
schema,
and compute the value to be contained in each column (field) of the new
event.
Comparable to a projection in SQL, where you use a SELECT statement to
specify the column expressions, and FROM to specify a single
source.
Union – allows you to combine multiple streams or windows that all
share a common schema into a single stream or
window.
Similar to SQL UNION operator.
Pattern – lets you watch for patterns of events within a single stream
or window or across multiple streams and windows. When ESP Server detects an
event pattern in a running project, it produces an output
event.
This uses the CCL MATCHING clause.