from a react query call I have a refreshInterval where I get a function call that returns the fresh data.
refetchInterval: (data) => (compareData(data) ? false : 1000),
const compareData(freshData) {
... would like access previous data to compare with freshData
.. if different stop interval
}
I want a way to get the previous data from the refecthInterval function. Is there a way to do this ?
So far all I can get back is the fresh data. I want to be able to compare my new fresh data with previous stale data and do a comparison.
I've seen something called isDataEqual that you can set on the config of the query but can't find any docs on how to use it.
Related
I'm relatively new to golang and could use some high-level tips on how to structure this. I'm trying to a build a REST API:
The user would provide a small JSON payload via POST method
The API compares the user’s input data against a reference dataset stored as a slice of structs and calculates a value
This value is returned to the user
Every hour a database is queried to and replaces the slice of structs dataset with another slice of structs dataset. Basically this refreshes the reference data
I'd like this refreshing job to be async so it doesn't slow down the user experience
I'm using the golang's Echo framework (https://echo.labstack.com/). Here is my attempt in golang-like pseudocode.
How would you structure this API to refresh the data hourly async?
To clarify, the part Im stuck on is the “query the DB every hour async in the background” bit. Im unsure how to do that in thos scenario.
func main() {
e := echo.New()
e.POST("/", func(something) {
// This func queries the DB and saves reference dataset result as a slice of structs
dataset := refreshDB()
// Does some calculations on input JSON data and reference dataset
result := doCalcs(inputJSON, dataset)
// Prep response in neat JSON
responseForUser := prepOutput(result)
return responseForUser
})
}
For async code in Go you can use a goroutine, to execute the code periodically you can use a ticker.
package main
import (
"fmt"
"time"
"sync"
)
var rwm sync.RWMutex
var sliceOfStructs []struct{/* ... */}
func main() {
go func() {
tick := time.NewTicker(time.Hour)
for range tick.C {
rwm.Lock()
sliceOfStructs = []struct{}{ /* refresh with new data */ }
rwm.Unlock()
}
}()
// start server
}
If sliceOfStructs needs to be accessible across multiple packages then you'll need to export it and move it to a non-main package, i.e. one that can be imported. And do the same for rwm.
Make sure that any code that reads sliceOfStructs invokes rwm.RLock before reading and rwm.RUnlock when done.
If you have more than one goroutine that needs to write sliceOfStructs then you should change rwm from sync.RWMutex to sync.Mutex.
So, I am making a query everything my context API is updated via a form selection update..
So, order of operation is like so.
User makes a change to a form by selecting (one of possible many) from dropdown.
Change updates "context api" which resaturates the parent component.
Because the form key/values changed, I fire a mutation.
Mutation returns a value. So far, great.
But, when I repeat step #1 - #4, another component flickers with that updated value because at some point the "const" that is expecting a value is undefined... THEN, it has a value..
So, like so..
has a value...
...query api call...
has no value
...returns query
has a value
const ProductPage = (props) => {
const { question } = useContextStateWhatever();
/* Queries */
const { data = {}, isFetched } = useProductUpdatePrice({ questions });
const value = derivePriceFromResponse(data.products);
return (
<SomeComponentRendered value={value} />
)
So, you can see between the "old value" and request in query, that the passed "value" will be undefined. Then query returns, updated value.
I was hoping the query will return any previous value, but the "queryKey" changes with every selection of the form. Deep queryKey.
I was hoping I wouldn't have to then put this value into local state from within a useEffect, or use useRef and create hook to hand back "previous" value until new value is ready.... That's not what react-query is for, right? I mean, shouldn't I be able to make a query call whenever the "context api" changes, and not expect this latency diff of undefined. Any strategies to over come this?
Since the "queryKey" is different (mostly for normal form interaction) for each query, I can see how it can't hand back a previous value until it resolves etc.. any ideas?
Any thoughts?
I think the keepPreviousData: true option is what you are looking for. If the query key changes, you will the get the data from the previous query key, along with an isPreviousData: true flag. The background update will still happen, and then you’ll get the data for the new query key once it arrives. The query will stay in isSuccess status the whole time.
I'm trying to fetch an array of strings I have saved on my database but I'm getting the array back with missing values, only the first value is shown inside of it. Here's the structure of my database:
Path: /users/uid/services <-- this is the array
Path: /services/uid <--service document
The code I'm using to retrieve the users is:
_getWorkers() async {
var query = await Firestore.instance.collection('users').where('services', arrayContains: widget.category['uid']).getDocuments();
query.documents.forEach((doc) {
workers.add(doc.data);
List<String> values = List.from(doc.data['services']);
print('services:' + values.toString());
});
var test = await Firestore.instance.collection('users').document('PtBD2EMSTodvlx6WHUx8QOHHLNA2').get();
print('actual services:' + test['services'].toString());
}
Both query and test get data back, but the services array only contains the first value.
Its difficult to answer without actually seeing the entire DB structure. But still on the outset i can see only one error with your code.
When you are trying to execute the where() call, try adding the snapshots to retrieve all relevant data.
Since await is also used, it is much better to call the listen() on it and then read the values to be added to the worker
Try using this below code in place of your first line.
await Firestore.instance.collection('users').where('services', arrayContains: widget.category['uid']).snapshots().listen((query)=>query.documents.forEach((doc)=>print(doc.data['services'])));
For some reason Firebase wasn't returning the updated array. Tested it again today and it worked with the same code. Sorry for bothering, thanks for the help anyways.
I'm trying to create an RHQ plugin to gather some measurements. It seems relativity easy to create a plugin that return a value for the present moment. However, I need to collect these measurements from files. These files are created on a schedule, for example one per hour, but they contain much finer measurements, for example a measurement for every minute. The file may look something like below:
18:00 20
18:01 42
18:02 39
...
18:58 12
18:59 15
Is it possible to create a RHQ plugin that can return many values with timestamps for a measurement?
I think you can within org.rhq.core.pluginapi.measurement.MeasurementFacet#getValues return as many values as you want within the MeasurementReport.
So basically open the file, seek to the last known position (if the file is always appended to), read from there and for each line you go
MeasurementData data = new MeasurementDataNumeric(timeInFile, request, valueFromFile);
report.add(data);
Of course alerting on this (historical) data is sort of questionable, as if you only read the file one hour later, the alert can not be retroactively fired at the time the bad value happened :->
Yes it is surely possible .
#Override
public void getValues(MeasurementReport report, Set<MeasurementScheduleRequest> metrics) throws Exception {
for (MeasurementScheduleRequest request : metrics) {
Double result = SomeReadUtilClass.readValueFromFile();
MeasurementData data = new MeasurementDataNumeric(request, result)
report.addData(data );
}
}
SomeReadUtilClass is a utility class to read the file and readValueFromFile is the function, you can write you login to read the value from file.
result is the Double variable that is more important, this result value you can calculate from database or read file. And then this result value you have to provide to MeasurementDataNumeric function MeasurementDataNumeric(request, result));
I'm building a form with Yii that updates two models at once.
The form takes the inputs for each model as $modelA and $modelB and then handles them separately as described here http://www.yiiframework.com/wiki/19/how-to-use-a-single-form-to-collect-data-for-two-or-more-models/
This is all good. The difference I have to the example is that $modelA (documents) has to be saved and its ID retrieved and then $modelB has to be saved including the ID from $model A as they are related.
There's an additional twist that $modelB has a file which needs to be saved.
My action code is as follows:
if(isset($_POST['Documents'], $_POST['DocumentVersions']))
{
$modelA->attributes=$_POST['Documents'];
$modelB->attributes=$_POST['DocumentVersions'];
$valid=$modelA->validate();
$valid=$modelB->validate() && $valid;
if($valid)
{
$modelA->save(false); // don't validate as we validated above.
$newdoc = $modelA->primaryKey; // get the ID of the document just created
$modelB->document_id = $newdoc; // set the Document_id of the DocumentVersions to be $newdoc
// todo: set the filename to some long hash
$modelB->file=CUploadedFile::getInstance($modelB,'file');
// finish set filename
$modelB->save(false);
if($modelB->save()) {
$modelB->file->saveAs(Yii::getPathOfAlias('webroot').'/uploads/'.$modelB->file);
}
$this->redirect(array('projects/myprojects','id'=>$_POST['project_id']));
}
}
ELSE {
$this->render('create',array(
'modelA'=>$modelA,
'modelB'=>$modelB,
'parent'=>$id,
'userid'=>$userid,
'categories'=>$categoriesList
));
}
You can see that I push the new values for 'file' and 'document_id' into $modelB. What this all works no problem, but... each time I push one of these values into $modelB I seem to get an new instance of $modelA. So the net result, I get 3 new documents, and 1 new version. The new version is all linked up correctly, but the other two documents are just straight duplicates.
I've tested removing the $modelB update steps, and sure enough, for each one removed a copy of $modelA is removed (or at least the resulting database entry).
I've no idea how to prevent this.
UPDATE....
As I put in a comment below, further testing shows the number of instances of $modelA depends on how many times the form has been submitted. Even if other pages/views are accessed in the meantime, if the form is resubmitted within a short period of time, each time I get an extra entry in the database. If this was due to some form of persistence, then I'd expect to get an extra copy of the PREVIOUS model, not multiples of the current one. So I suspect something in the way its saving, like there is some counter that's incrementing, but I've no idea where to look for this, or how to zero it each time.
Some help would be much appreciated.
thanks
JMB
OK, I had Ajax validation set to true. This was calling the create action and inserting entries. I don't fully get this, or how I could use ajax validation if I really wanted to without this effect, but... at least the two model insert with relationship works.
Thanks for the comments.
cheers
JMB