I'm starting a project and setting the code style guide. I like the second of the two below, but I'm wondering if there is a difference in the way these two statements are executed? Is the second one slower, or is the whole chain evaluated before any call to the database happens? (I only see a single frame in the socket)
Style 1:
db.child(`data/projects/${currentProject}/boxes/${newBoxId}`).set(true);
Style 2:
db
.child('data')
.child('projects')
.child(currentProject)
.child('boxes')
.child(newBoxId)
.set(true);
There is no performance difference between the two.
Calling child() does not require the client to connect to the server, it's a pure client-side operation. So you can do whatever is most readable in your code.
If I have a set of static segments in the path, I typically combine them in a single child() call. But when there is a dynamic segment, I prefer to put that into its own child() call to prevent having to concatenate strings.
ref.child('users').child(authData.uid).child('documents/passport').on('value'...
Related
The docs only show examples for when a component promotes a single input. How do I use src_indices to indicate that only one of my promoted inputs takes a certain slice?
p.model.add_subsystem('ComputeWakePosition', ComputeWakePosition(num_wake_points_per_side=4),
promotes_inputs=['wake_upper_lengths',
'wake_lower_lengths',
'wake_upper_angles',
'wake_lower_angles',
'displaced_cw_coordinates'], <-- I want to specify src_indices for this input only.
promotes_outputs=['upper_wake_coordinates',
'lower_wake_coordinates'])
I think I would be able to just use connect for that input, but given that everything else I've written doesn't use it, it'd be nice if there was a way to avoid it.
There is a function called promotes that you can call on your group after you've added a subsystem. In your code above, you could remove the promotion of the displaced_cw_coordinates variable from your add_subsystem call and make a separate call something like this p.model.promotes('ComputeWakePosition', inputs=['displaced_cw_coordinates'], src_indices=[2,4,6,8])
I want to write custom tracer adding functionality to track duration (time spent on execution) of some routine.
I am thinking about using Dictionary<object, DateTime>.
Here is a pseudo code:
// adding current time to the dictionary for key 'anyObject'
Tracer.SaveCurrentTime(anyObject);
// doing something
// adding related line to a log file and removing key 'anyObject'and its value from the dictionary
Tracer.TraceTimeSpent(anyObject);
At first I liked it because this approach would work for different threads and classes.
But now I am wondering if it is a good idea at all? Calling SaveCurrentTime without calling TraceTimeSpent would leave key/value pair in the dictionary until the end of the process execution.
It is a bad practice and I will regret using it in my applications?
In my application I have multiple variables that need to be accessed globally from the different functions of my script:
var a=1,b=2,c, ...;
Where "c" undefined at the beginning and takes value produced by some of the functions during scripts execution.
In order to declare them from within my "main" function I'm trying to use window object:
window.a=1;
window.b=2;
window.c;
This works, however I'm not sure if such approach is correct.
And is there is a way to avoid creation multiple window objects for each variable and combine them into more compact structure? Something like:
window.a=1,.b=2,.c;//---of course-this doesn't work
I was asking this question today too. It used to be the way when I last wrote javascript (mid-90s) and still seems to be the case see this resource
We want to remove elements from Map bin based on size. There will be multiple threads which will try to do above operation. So writing an UDF to do this operation will make it synchronized between threads. But remove_by_rank_range is not working inside lua. Below is the error iwe are getting:
attempt to call field 'remove_by_rank_range' (a nil value)
sample lua code:
function delete(rec)
local testBinMap = rec.testBin
map.remove_by_rank_range(testBinMap, 0, 5)
end
The Lua map API does not include most of the operations of the Map data type, as implemented in the clients (for example, the Java client's MapOperation class).
The performance of the native map operations is significantly higher, so why would you use a UDF here, instead of calling remove_by_rank_range from the client?
The next thing to be aware of is that any write operation, whether it's a UDF or a client calling the map remove_by_rank_range method, first grabs a lock on the record. I answered another stackoverflow question about this request flow. Your UDF doesn't give any advantage to the problem you described over the client map operation.
If you want to cap the size of your map you should be doing it at the very same time you're adding new elements to the map. The two operations would be wrapped together with operate() - an insert, followed by the remove. I have an example of how to do this in rbotzer/aerospike-cdt-examples.
I am experimenting with firebase-queue. I saw the option for sanitizing. It's described in the doc as
sanitize - specifies whether the data object passed to the processing
function is sanitized of internal keys reserved for use by the queue.
Defaults to true.
What does it mean?
I am getting an error for not specifying { sanitize : false }
When the sanitize option is set, the queue sanitizes (or cleans) the input provided to the processing function so that it resembles that which the original client placed onto the queue, and doesn't contain any of the keys added by the implementation of the queue itself.
If, however, you rely on a key (usually the keys starting with an underscore, e.g. _id) that is added by the queue, and not the original client, you need to set sanitize: false so those keys are returned to your function and they're not undefined.
You can clearly see the difference with a simple processing function that just performs a console.log(data).
A quick note about why these keys are removed by default: Reading or writing directly to the location (as it looks like you're perhaps doing, by passing undefined into the client SDK child() method instead of data._id) is generally a bad idea from within the worker itself as writes performed directly are not guarded by the extensive transaction logic in the queue to prevent race conditions. If you can isolate the work to taking input from the provided data field, and returning outputs to the resolve() function, you'll likely have a better time scaling up your queue.