Using StreamBase Operators

Provides a view into data in a moving window, where you might want to compare, sum, average, or count that data. For example, you could:

Reorders tuples by using an approximate buffered sort. For example, you could reorder trades by time where they are potentially out of order.

Sends tuples to different downstream branches based on tuple values, or remove from the stream any tuples with values that do not correspond to a defined set of values. For example, you could allow only those trades of 10000 shares or more to pass into a particular output stream

Combines tuples, using a common key value, that were previously split up into separate branches. For example, you could gather together the results of tests performed on one trade, and output the status of each individual test.

Adds timer tuples on the same stream as your data tuples, generally so that downstream operations can occur even if there is a lull in the incoming data. The Heartbeat operator detects late or missing tuples. Like the Metronome operator, it uses the system clock and emits output tuples periodically, but Heartbeat also calibrates the system clock using the input stream. The operator sends any tuples on its input stream through to the output stream, updating its internal clock for each tuple. If an expected input tuple does not arrive within the configured interval plus a timeout period, then the Heartbeat operator synthesizes a tuple with all null data fields (except for the timestamp) and emits it.

Combines tuples where there can be more than one match per tuple. For example, you could generate an alert when trades in a given stock on Reuters and Comstock differ by more than a pre-set amount during any 60 second period.

Processes one tuple at a time through a section of the application, to achieve mutual exclusion. For example, you might use the Lock and Unlock pairs to ensure sequence coordination, or to protect shared data against concurrent writes, within the set of operators that reside between the starting Lock operator and the ending Unlock operator.

Transforms tuples by performing math or logical functions (such as a currency conversion), or remove or rename fields in your schema. For example, from a stream that contains stockname, symbol, description, volume, and price, you could use a Map operator to output a stream containing symbol, name, and cost.

Combines two streams into one with ordering by a field value (such as time). For example, you could interleave trades from two different feeds based on the time of the trade.

Delivers output tuples periodically based on the system clock, at an interval you specify. In the same way musicians use a metronome to indicate the exact tempo of a piece of music, you can use the StreamBase Metronome operator to control the timing of downstream operations by a connected component.

Applies pattern-matching queries across input streams. For example, you can detect when key events occur on one stream concurrently with sensitive operations on another stream.

Reads from or writes to a Query Table. The Query Table can reside in memory (where the data is not persisted after server shutdown) or on disk (where the data can persist between StreamBase Server sessions). The purpose of Query operators and Query Tables is to let you share data and maintain state across the StreamBase application, or between containers.

Adds a field to each passing tuple, which field contains a unique identifier generated for that tuple. You can use the identifier field downstream as required by your application, such as to generate a keyword for tuples before storing them in a Query Table.

Splits its incoming stream into two or more outgoing streams that execute in a guaranteed specific order. Each incoming tuple is sent first to output port 1, then to output port 2, and so on. By contrast, you can also form a split by drawing multiple arcs from operator output ports. However, in this case, the order in which tuples proceed out multiple arcs is not known and not guaranteed. By using a Split operator, you can obtain a guaranteed processing order.

Combines two streams with the same schema into one stream, with no particular interleaving as in Merge. For example, you could interleave trades from two different feeds.

This is a global Java operator that provides a way for StreamBase applications to run external commands by specifying each command and command option in a table.

This is a global Java operator that provides a way for StreamBase applications to run external commands by specifying the command line to be run as a StreamBase expression string. The advantage of this version is that you can use expressions to calculate, increment, or augment portions of the command line argument strings.