将文本文件中的数据存储到Esper引擎中以用于EPL

Question

I have a text file which has lines in this format:

XYZ 120 
ABC 200 
...

Essentially, one 3 character string and an integer value. Their format will not change but the value of the integer might depending on the events.

I would like to store the information from this file into the engine so that I could use it in EPL statements. I want to be able to compare the incoming events with my list and act when certain conditions occurs.

That is, every time an events occurs, I check my data to see if its in my list. Say an event has code XYZ, I check and see that I have it, I perform operations and then change the value of the XYZ's integer. Updating the file is not necessary, it's just a mean to feed the data into the engine.

I believe there are a few possible ways to go about this but I am not sure how their implementation is to be completed and which is the best practice.

Option 1: Using the method invocation as explained in

5.14. Accessing Non-Relational Data via Method, Script or UDF Invocation

I followed the instructions about providing the method and the metadata but I am quite confused how to iterate the returned data within the EPL statement? The return of my method is:

Collection<MyStock> stocks 

where MyStock is the [String, Integer] pair.

where event.code = stocks.code 

obviously does not work because stocks is a collection

So how to iterate through the collection within the EPL?

Option 2: Alternatively, I can probably feed the file into a Map and then save the Map into the engine as a variable?

I get stuck with the iteration here as well. I believe I might have missed crucial part in those concepts and I'd like to be pointed at the right direction. Better yet, a working example of something similar would be nice.

Possible solution:

@Name('createTable')
create table HolderTable(code string primary key, amount int);

@Name('insertTable')
insert into HolderTable select code, amount from MyStock; 

@Name('compareEventsWithTable')
@Subscriber(className='subscribers.MySubscriber')
on TickEvent as tick
select code, amount from HolderTable
where tick.stockCode = code;

Answer 1

It sounds like you want to collect data and use the collected data in multiple queries. You can use a named window or table for that.

create window StockWindow#unique(stock) (stock string, value double);

insert into StockWindow select stock, value from IncomingEvent;

select MyLib.computeSomething(select window(*) from StockWindow) from StockWindow;

The engine calls the "computeSomething" function provided by class "MyLib" and passes the window contents to that, when StockWindow has a new event entering the window.