In an InfluxDB measurement, how can the field values of points matching a query be updated? Is this still not easily doable as of v1.6?
As the example in that GitHub ticket suggested, what's the cleanest way of achieving something like this?
UPDATE access_log SET username='something' WHERE mac='xxx'
Anything better than driving it all from the client by updating individual points?
Q: How can the field values of points matching a query be updated? Is this still not easily doable as of v1.4?
A: From the best of my knowledge, there isn't an easy way to accomplish update in version 1.4 yet.
Field value of a point can only be updated by overriding. That is, to overwrite its value you'll need to know the details of your points. These details include its timestamp and series information, which is the measurement it reside and its corresponding tags.
Note: This "update" strategy can only be used for changing the field value but not tag value. To update a tag value you'll need to first DELETE the point data first and rewrite the entire point data with the updated tag and value.
Q: Anything better than driving it all from the client by updating individual points?
A: Influxdb supports multi-point write. So if you can build a filter to pre-select a small dataset of points, modify their field values and then override them in bulk.
Update is possible and would take the format:
INSERT measurement,tag_name=tag_value_no_quotes value_key_1=value_value_1,value_key_2=value_value_2 time
for example where I want to update the line with tag my_box at time 1526988768877018669 on the box measurement:
INSERT box,box_name=my_box item_1='apple',item_2='melon' 1526988768877018669
Related
I am working with Django and I am a bit lost on how to extract information from models (tables).
I have a table containing different information from various sensors. What I would like to know is if it is possible from the Django models to obtain for each sensor (each sensor has an identifier) the last row of data (using the timestamp column).
In sql it would be something like this, (probably the query is not correct but I think you can understand what I'm trying)
SELECT sensorID,timestamp,sensorField1,sensorField2
FROM sensorTable
GROUP BY sensorID
ORDER BY max(timestamp);
I have seen that the group_by() function exists and also lastest() but I don't get anything coherent and I'm also not clear if I'm choosing the best form.
Can anyone help me get started with this topic? I imagine it is very easy but it is a new world and it is difficult to start.
Greetings!
When you use a PostgreSQL database, you can make use of the .distinct(..) method [Django-doc] of the queryset where you add fields that determine on what these should be distinct.
So you can obtain the latest sensors in Django with:
SensorModel.objects.order_by('sensor', '-timestamp').distinct('sensor')
We thus order by sensor (which is required for a .distinct(..)), and then in case of a tie (so two times the same sensor), we order on the timestamp in descending order, hence we pick the latest SensorModel object for that sensor.
Using Slick 3, I want to update my row depending on the property provided by the user. Say, I have 2 properties email and name. If email and name are provided I will update both properties in the database. If either one is provided I will only update the one provided and leave the other untouch.
I found what I want here,
Conditonally UPDATE fields with Slick String interpolation
but I do not want to manipulate the query string directly. Is this the only way? I prefer to use filter and update methods. Thanks
I could not find an answer fast enough and I relented. I use multiple update configurations instead of a generalized composing update. This is bad as the number of configurations depend on 2 power of the number of parameters variant. It will become unwieldy and explode. Fortunately, at the moment, I have 2 parameters to manage.
One possible workaround for this is to get the record first, update its fields in-memory, and then pass it to Slick update. It'll generate an SQL UPDATE for all the fields.
Notice that it should be done in transaction and might have different semantics depending on your transaction isolation level.
I am having difficulty with a duration field on my form/table.
The users need to indicate in HH:MM how long a meeting took.
What datatype should the column have in the Table. Currently it is TIMESTAMP
How can I make the field have an input mask of 'HH:MM'. What I would like is for the user to be able to type '0130' and the field format it to '01:30' immediately.
Reporting on these times is required so I assume that entering the data as VARCHAR will not help.
Honestly, this is not such an easy subject as people might think it is, and probably more from a user interface point of view than technically.
The easiest way out? The apex datetimepicker. And honestly, if you're new to the technology I'd advise you to use this, especially if you want to steer clear from javascript/jquery initially.
Let's put it this way: the datepicker is fine and works good, but time is really not that fantastic.
Not all that hot right. The value in the input item does not change until you hit 'Close'. The time component seems like a last second sloppy addition honestly. It works, however. (But I'd still set the field to readonly so that a user can not enter text directly.)
Allowing text to be entered means it needs to be validated according to the correct format mask. And format masks differ between those in jQuery (the datepicker) and those in Oracle, and it might be possible that your oracle format mask is not possible in the datepicker, adding even more complexity. There is also no 'live' date validation (nor datetime), there is only the builtin item validation which will check the format mask and which fires on submit.
Anyway, I'd say take a look at it. Set your item to be displayed as a Date Picker, and use the format mask under settings to get the datetime picker:
Now you can push it further of course, though it'll cost some effort. There are several options though.
Personally, when I've implemented date+time I've always split the date from the time in 2 fields. 1 with the date component, and one with the time component, while keeping the item with the original value hidden (so 3 items total). I then use the datepicker on the date item, and use jquery timepicker plugins on the time item. On submit I then add the 2 values together and parse them in a date, and put this value in the original item again (to allow the standard processing to work on items with source set to database column).
One example of a timepicker is here, another one here. They're both not that hard to implement. They have good documentation too. I don't want to dive in the implementation of it here though, I advise you take a look at it first and see how much it scares you. (I'd set up an apex demo but am a bit pressed for time at the moment).
For example, using Trent's (second link) plugin:
put the js file in the apex images directory. I made a folder "/custom" in my case
add the required js files to the page (assuming apex 4.2, put this in javascript file urls)
#IMAGE_PREFIX#libraries/jquery-ui/1.8.22/ui/jquery.ui.slider.js
#IMAGE_PREFIX#custom/jquery-ui-timepicker-addon.js
use onload code such as this to initialize a field
$("#P95_DEPARTURE_TIME").timepicker({hourGrid: 4,minuteGrid: 10});
It'll end up looking as this:
Any further interaction between pickers will need to be handled in javascript code if you want it live. Don't forget server validations.
As for items, my hidden date item has format mask DD-MON-YYYY HH24:MI. Format masks are important, because items are bind variables, and bind variables are varchar2. The value in the html form is also just that, text.
For example, this is on my displayed date item, with a similar setup for the time item:
Then in an after-submit computation I glue the values together again and put them in the m that'll save the value to the database:
:P95_DEPARTURE_DATE_DISP||' '||:P95_DEPARTURE_TIME
This is just a short guide on the setup though, but might be interesting once you're a bit more familiar with the product.
There are also 2 timepicker plugins on apex-plugin, but honestly I don't find them interesting at all when compared to these already existing fine jquery plugins.
Give it some thought and look at it.
If quarters are enough..
item: text field with autocomplete
SELECT ss|| ':' || dd ss_dd
FROM
(SELECT to_char(trunc(sysdate)+(level - 1)/ 24,'HH24')ss
FROM dual CONNECT BY level <= 24),
(SELECT lpad(mod(15 * level, 60), 2, '0') dd
FROM dual CONNECT BY level <= 4)
APEX 4.2: Just to shed some light for any future viewings; now there are loads of Apex plugins for the purpose of picking Date/Time or both returning variations of date time formats as you would required. For e.g. as in your case HH:MM or HH24:MI.
I have personally used TimePicker plugin from http://www.apex-plugin.com which I have no problem in recommending.
I'm trying to find the best way to go about my problem and I would love your input. I am trying to allow users to scan multiple barcodes into a text area. After they are submitted they are split into an array. The user then inputs how many iterations of each value in the array are to be inserted into a MySQL database. I've achieved this using PHP and session variables, looping through the array one step at a time. With Django I've found it a little more difficult and I am wondering if I should just have a "temporary" table in my database that gets refilled with the values from the array of barcodes. The following pages then pull each value from the table instead of using any sort of session variables.
Edit:
I apologize for the confusing question. Let me try and clear it up a bit:
I need to render a view based on each value in the user-submitted array. When it is first submitted, a view is rendered for the first value. When the user hits "Next" a view will be rendered for the second value in the array, and so on.
As for the database issue, each value can have two "types." The user will declare how many of each type is added to the database in each of the views I am trying to render.
Thank you.
this is nothing about django.
forget that temporary table.
add a field "filled" to ur table
select 1st not-filled row, and show "refill" page by this row
then update user input number back to db, set "filled" to "true" at same time.
You probably can port your PHP solution using a Django session object.
I'm not sure if that "one item at a time" is a feature or a "it was easier to code that way" thing, but in the second case - you may want to use Django Formsets to display all items at once and avoid looping through the array.
I have a simple database and want to update an int value. I initially do a query and get back a ResultSet (sql::ResultSet). For each of the entries in the result set I want to modify a value that is in one particular column of a table, then write it back out to the database/update that entry in that row.
It is not clear to me based on the documentation how to do that. I keep seeing "Insert" statements along with updates - but I don't think that is what I want - I want to keep most of the row of data intact - just update one column.
Can someone point me to some sample code or other clear reference/resource?
EDIT:
Alternatively, is there a way to tell the database to update a particular field (row/col) to increment an int value by some value?
EDIT:
So what is the typical way that people use MySQL from C++? Use the C api or the mysql++? I guess I chose the wrong API...
From a quick scan of the docs it appears Connector/C++ is a partial implementation of the Java JDBC API for C++. I didn't find any reference to updateable result sets so this might not be possible. In Java JDBC the ResultSet interface includes support for updating the current row if the statement was created with ResultSet.CONCUR_UPDATABLE concurrency.
You should investigate whether Connector/C++ supports updateable resultsets.
EDIT: To update a row you will need to use a PreparedStatement containing an SQL UPDATE, and then the statement's executeUpdate() method. With this approach you must identify the record to be update with a WHERE clause. For example
update users set userName='John Doe' where userID=?
Then you would create a PreparedStatement, set the parameter value, and then executeUpdate().