If I have a Cloudant MapReduce view with year/month/day as the key array, can I query the dataset just by month or just by day?
No. You can query by y/m/d or by y/m or by y.
In other words, you are allowed to omit fields, but you cannot have gaps, so you have to start omitting from the right.
Examples:
Querying by y/m/d -- key=[2022,5,20] finds everything for one day
Querying by y/m -- startkey=[2022,1]&endkey=[2022,2] finds everything in January
Querying by y -- startkey=[2021]&endkey=[2022] finds everything in 2021
Related
Good day all,
I am trying to filter todays result in SQL table to a collection in powerapps. The column "dt" represents the column in sql of datetime type.
This is my powerapps filter:
ClearCollect(myCollectionName, Filter(myDatasource, Text(dt,"dd/mm/yyyy") = Text(Now(),"dd/mm/yyyy" )));
Seems like the collection is still empty even there is data for today in sql. May I know if my approach is the correct way in filtering?
Short answer: the data is likely being changed based on the client time zone. To fix it, you can update it by applying the time zone offset to the data from the SQL table, something along the lines of:
ClearCollect(
myCollectionName,
Filter(
myDatasource,
Text(DateAdd(dt, TimeZoneOffset(dt), Minutes), "dd/mm/yyyy") =
Text(Now(), "dd/mm/yyyy")))
Long(er) answer: the datetime type in SQL Server represents an absolute value of date and time. For example, the value '2021-12-23 09:30:00' represents 9:30 in the morning of the 23rd day of December, 2021 - at any part of the world. The date/time type in Power Apps, however, represents a point in time, typically referring to the local time where the app is being executed (or created). For example, if I selected that value and I'm in the US Pacific Time Zone (UTC-08:00), that would represent the same value as if someone in London (UTC+00:00) selected 2021-12-23 17:30:00. Since the two types represent different concepts, we may have mismatches like you are facing. To fix this, we can either use a type in SQL Server that has the same semantics as Power Apps (for example, 'datetimeoffset'), or adjust the time when it is being transferred between SQL and Power Apps.
The blog post at https://powerapps.microsoft.com/en-us/blog/working-with-datetime-values-in-sql explains in more details how to work with date/time values in SQL and Power Apps.
Are you able to use MongoDB to combine rows of data into one row?
I'm using dates with year, month, day and hour. The data is shown per hour. Is there a way to combine data of the hours into just one day with data. I would basically remove the hour column and sum the hour data into per day data.
I'm not sure what you mean by "the data is shown per hour" - do you mean it's stored in the database that way?
MongoDB doesn't have rows and columns - the equivalent of a row is a document, and the column equivalent is a field. Unlike in traditional SQL, a field isn't just one piece of information (a string, number/date, boolean, null, etc). It can be more than one piece of data - it can be an array, or a document, or an array of documents, etc.
Anyway, based on the small amount of information I have on your situation, I'd absolutely design the data with the bucket pattern. https://www.mongodb.com/blog/post/building-with-patterns-the-bucket-pattern
You could $unset the 'measurements' array and just keep the sum/count fields if that's what you want.
If your data is already set in stone, then I'd use an aggregation pipeline to group all the documents ('rows') together - the group _id would be year, month, day, and you could sum/count/min/max/etc the data in the group too.
Alteryx
Table 1 is a google sheet file. It has x fields with primary key.
Every day to that table is added the weekday with the x data
For example:
Monday
Tuesday (is added on Tuesday) and so on.
My problem is that my workflow has a formula that does calculations with all the Weekdays.
Example:
Balance = All_Income - Monday - Tuesday - Wednesday - Thursday - Friday - Saturday - Sunday
But today for example, in the google sheet data I don't have the other weekdays except Monday and Tuesday, so I get the error "Unknown Variable" for Thursday.
I've inserted a Text Input and added all the weekdays.
I want to (Append maybe) these two data streams together so that I have all the weekdays there.
So if I run the calculations I have all the weekdays there.
Right now that formula works only on Sunday, when all weekdays are inserted as columns.
Any idea how to achieve this?
(p.s Creating the weekdays as columns in the google sheet with empty rows is not an option).
I managed to do it by creating a Text Input with the same column names (headers) as the other Data Source and performing a union.
Apparently I needed to perform a IF statement to check all Weekdays if they exist and replace the null values with.
If anyone encounters the same error, feel free to contact for help :)
Use the Transpose tool to verticalise the days of the week. Then Summarize using the primary key and sum the [value] field. That will give you the balance regardless of which days of the week are present in your worksheet. This technique applies to any problem in which one needs to aggregate multiple fields which may or may not be present or known.
Here is the simplest path to victory:
1. Input worksheet.
2. Connect Transpose tool.
3. In Transpose Key Columns, select only primary key.
4. In Transpose Data Columns, deselect all fields except for days of week and Dynamic or Unknown Columns. This will still work even if the worksheet doesn't have all the days of the week because as they come in, the Dynamic or Unknown Columns option will select them as Data columns.
5. In Transpose Missing Columns, select Ignore.
6. Connect Summarize tool.
7. In Summarize, group by primary key and sum on [Value] field.
From here, you can rename the sum_value field to Balance or something else friendly. You can also use a Join tool, joining on primary keys, to the original worksheet to get back to where you started with the new aggregated value.
How do I setup an index on DynamoDB table to compare dates? i.e. for example, I have a column in my table called synchronizedAt, I want my query to fetch all the rows that were never synchronized (i.e. 0) or weren’t synchronized in the past 2 weeks i.e. (new Date().getTime()) - (1000 * 60 * 60 * 24 * 7 * 4)
It depends by the other attributes of your table.
You may use an Hash and Range Primary Key if the set of Hash values is relatively small and stable; in this case you could filter the dates by putting them in the Range, but anyway the queries will be done by specifying the Index also, and because of this it may or may not make sense to pre-query for all the Index values in order to perform a loop where ask for the interesting Range (inside of the loop for each Index value).
An alternative could be an Hash and Range GSI. In this case you might put a fixed dumb value as Index, in order to query for the range of all Items at once.
Lastly, the less efficient Scan, but with large tables it will be a problem (the larger the table the more time the Scan will take to complete).
I had similar requirement to query on the date range. In my case date range was only criteria. The issue with DynamoDB is you cannot create an Index with Just Range key. It always require Hashkey and Query on such index always expect equal to condition for Hashkey.
So I tricked the DB. I created a Key as Century and populated with century year of the date. For example 1 Jan 2019, century key value is 20. For 1 Jan 2020 century key value is also 20. Very easy to derived from any date. Then Created GSI with Hashkey as Century and RangeKey as date. While querying it is very easy to derive century from date range and Build query condition Hashkey as century and date range. Since I am dealing with data no more than 5 years, trick won't fail for next 75 years. :)
It is not so "nice to have" workaround but it work for me quite well. May be it will help someone else as well.
I am doing a kind of room reservation system where a collection is containing documents which contains two dates : a begin date and an end date.
I would like to be able to find all the reservation which begin date is between two dates and end date is also between two dates.
I have used MongoDB compound indexes thus I am indexing start date and end date field.
However I am wondering if I can imporove my query performnce by using GEO2D indexes. For this we could convert begin date and end date to unix time, then each booking is a point whose position is (start date, end date).
Using the $within operator it makes it possible to query for reservation which are in a range of start date AND end date.
Since GEO index are more used for spatial data I guess, would it make sense to use them for this specific use-case ?
Finally since GEO2D indexes are inplemented as B-Trees in MongoDB and not as R-Trees, what is the difference between traditional indexes and this GEO one?
It is an interesting idea, but I don't think it will help your search speed or efficiency. Geo indexes in MongoDB are just B-trees applied to a geohash, where the geohash is just a mechanism to convert something that is two dimensional to something that is one dimensional, such that it can be used by B-trees. Geohashing is a powerful concept but has some peculiarities in that points that are close together could end up in totally different buckets, which can make searching for the x nearest points to a point quite inefficient, as 9 boxes have have to searched around your point of interest. A within query would have the same issues.
I would have thought that sharding on a date column (possibly as unix time) would be a more efficient way to improve performance, though there are some caveats around using a datatype that is monotonically increased as a shard key, such as a timestamp, see MongoDB shard keys.