existsSubscriptionTopic

existsSubscriptionTopic([server], tableName, [actionName])

Alias: existSubscriptionTopic

server (optional) is a string indicating the node alias of the subscribed stream table, or the handler of a remote call connection. If server is not specified or an empty string, it means the streaming data is from the local server.

tableName is a string indicating the name of a shared stream table.

actionName (optional) is a string indicating the name of the subscription task. actionName can only contain letters, numbers and underscores. If the actionName is specified when the subscription is created, it must also be specified here.

Check the existence of a subscription topic of a shared stream table. Return "true" if the subscription topic exists, "false" if it doesn't.

t=streamTable(1000000:0,`date`time`sym`qty`price`exch,[DATE,TIME,SYMBOL,INT,DOUBLE,SYMBOL])
share t as trades
trades_1=streamTable(1000000:0,`date`time`sym`qty`price`exch,[DATE,TIME,SYMBOL,INT,DOUBLE,SYMBOL])
subscribeTable(tableName=`trades, actionName=`vwap, offset=-1, handler=append!{trades_1})
existsSubscriptionTopic(,`trades,`vwap)
// output
true