Projections on category vs joining by $et

EventStoreDB
1

Hi,

Can I ask, In a projections which is most efficient to use out of these two examples?

fromStreams([

“$et-ProcessStepsCounted”,

“$et-ProcessStarted”,

“$et-ProcessStepStarted”,

“$et-OptionalProcessStepStarted”,

“$et-ProcessStepCompleted”,

“$et-ProcessCompleted”,

“$et-ProcessFailed”,

“$et-ProcessWarned”,

“$et-AllProcessStepsStarted”

]).when({

‘$any’: function (s, e) {

outputToStreams(e);

}

});

or

fromCategory(‘process’)

.when({

‘ProcessStepsCounted’: function (s, e) {

outputToStreams(e);

},

‘ProcessStarted’: function (s, e) {

outputToStreams(e);

},

‘ProcessStepStarted’: function (s, e) {

outputToStreams(e);

},

‘OptionalProcessStepStarted’: function (s, e) {

outputToStreams(e);

},

‘ProcessStepCompleted’: function (s, e) {

outputToStreams(e);

},

‘ProcessCompleted’: function (s, e) {

outputToStreams(e);

},

‘ProcessFailed’: function (s, e) {

outputToStreams(e);

},

‘ProcessWarned’: function (s, e) {

outputToStreams(e);

},

‘AllProcessStepsStarted’: function (s, e) {

outputToStreams(e);

}

});

Thanks

2

The first should be but as always “it depends”.

Are you using the $et events for other things? If not using them means that you can turn of the byeventtype projection then the second is definitely better.

3

Should we be turning off the by event type projection then If we don’t need it?

4

Always turn off projections if you know you will never use them. They only take up resources (both on the cpu/memory and make the database larger) and can also increase the startup time of projections when a node failover occurs.