deleteCache()

Syntax

deleteCache (cacheName, index)

Parameters

Usage

Deletes a row at a particular location (specifed by the index) in the event cache. This index is 0 based. The function takes an integer as its argument, and the function removes the row. The function does not produce an output. Specifying of an invalid index parameter will result in the generation of a bad record.

Example

This example obtains the top 3 distinct prices per trading symbol. In order to accomplish this task, the example makes use of the getCache(), cacheSize() and deleteCache() functions.

CREATE SCHEMA TradesSchema (
    Id integer, 
    TradeTime date,
    Venue string,  
    Symbol string, 
    Price float, 
    Shares integer
)
;

CREATE INPUT WINDOW QTrades SCHEMA 
TradesSchema PRIMARY KEY (Id)
;
CREATE FLEX flexOp
    IN QTrades
    OUT OUTPUT WINDOW QTradesStats SCHEMA TradesSchema PRIMARY KEY(Symbol,Price)
    BEGIN
       DECLARE
          typedef [integer Id;| date TradeTime; string Venue; 
             string Symbol; float Price; 
             integer Shares] QTradesRecType;
          eventCache(QTrades[Symbol], manual, Price asc) tradesCache;
          typeof(QTrades) insertIntoCache( typeof(QTrades) qTrades )
          {
             integer counter := 0;
             typeof (QTrades) rec;
             long cacheSz := cacheSize(tradesCache);
             while (counter < cacheSz) {
                rec := getCache( tradesCache, counter );
                if( round(rec.Price,2) = round(qTrades.Price,2) ) {
                   deleteCache(tradesCache, counter);
                   insertCache( tradesCache, qTrades );
                   return rec;
                   break;
                } else if( qTrades.Price < rec.Price) {
                   break;
                }
                counter++;
            }
            if(cacheSz < 3) {       
               insertCache(tradesCache, qTrades);
               return qTrades;
            } else {
               rec := getCache(tradesCache, 0);
               deleteCache(tradesCache, 0);
               insertCache(tradesCache, qTrades);
               return rec;
            } 
            return null;
         }
      END;

      ON QTrades {
         keyCache( tradesCache, [Symbol=QTrades.Symbol;|] );
         typeof(QTrades) rec := insertIntoCache( QTrades );  
         if(rec.Id) {
            if(rec.Id <> QTrades.Id) {
               output setOpcode(rec, delete);
            } 
            output setOpcode(QTrades, upsert);
         }
     };
    END;