I have to do a job with Talend, but I'm a beginner and the software is very complex, I'm a bit lost.
My current problem is to join multiple tSplitRow into one output excel file.
I don't know if I must use tMap? How to configure it? Or if another object exist to do that.
Each tSplitRow has the same structure: LastName,FirstName,Course,Grade.
My current structure
Thank's for help.
Since your components have the same structure, you can use tUnite to do a union of your rows. It takes multiple input links, and has a single output.
Related
i have multiple part folders each containing parquet files (ex given below). Now across a part-folder the schema can be different (either the num of cols or the datatype of certain col). My requirement is that i have to read all the part folders and finally create a single df according to a predefined passed schema.
/feed=abc -> contains multiple part folders based on date like below
/feed=abc/date=20221220
/feed=abc/date=20221221
.....
/feed=abc/date=20221231
Since i am not sure what type of changes are there in which part folders i am reading each part folder individually then comparing the schema with teh predefined schema and making the necessary changes i..e, adding/dropping col or typecasting the col datatype. Once done i am writing the result into a temp location and then moving on to the next part folder and repeating the same operation. Once all the part-folders are read i am reading the temp location at one go to get the final output.
Now i want to do this operation parallely, i.e., there will be parallel thread/process (?) which will read part-folders parallely and then execute teh logic of schema comparison and any changes necessary and write into a temp location . Is this thing possible ?
i searched for parallel processing of multi-dir in here but in majority of the scenarios they have same schema across dir so somehow they are using wildcard to read the input path location and create the df, but that is not going to work in my case. The problem statement in the below path is similar to mine but in my case the num of part folders to be read is random and sometimes over 1000. Moreover there are operation involved in comparing the fixing the col types as well.
Any help will be appreciated.
Reading multiple directories into multiple spark dataframes
Divide your existing ETL into two phases. The first one transforms existing data into the appropriate schema, and the second one reads the transformed data convenient way (with * symbols). Use Airflow (or Oozie) to start one data transformer application per directory. And after all instances of the data transformer are successfully finished, run the union app.
Here is my issue: I often need to compare the same postgresql tables (or views that depend on it) between some ETL code refactoring to check for non regressions in my developments.
Let's say I have an ETL code I want to refactor, which regularly uploads data in a table. Currently, once my modifs are done, I often download my data from postgresql as a .csv file as a first step, then empty it, fill it again using my refactored code, and download the data again. Then, I compare the .csv files using for instance Python in a Jupyter Notebook.
That does not seem like the way to go at all. That notably supposes I am the only one to use that table during the operation, and so many other things I can't list them all here.
Is there a better way to go ?
It sounds to me like you have the correct approach. There's no magic to the CSV export operation: whatever tool you use runs a query and formats its resultset into the file. Any other before-and-after comparison operation would have to run the same query.
If you're doing this sort of regression test on an active database, it's probably wise to put some sort of distinctive tag on your test records, maybe prepend ETLTEST- to your customer names, so it's ETLTEST-John Bull. Then you can make your queries handle only your test records. And make sure you do something reliable for ORDER BY.
Juptyer seems a complex way to diff your csv files. Most operating systems have lightweight fast difftools.
At the moment I have a lookup table in a Simulink model which is reading the first and second columns from the workspace; in other words, I put the names of my vector variables in these fields. Then, I generated the code using rsim.tlc, run the batch and got the expected results. Nevertheless, when I try to run the batch again changing the vectors (they have different length in comparison with the ones I used when compiled the executable), I always get a message which says that the checksum number mismatches. I already verified if the rtP structure correctly reads the new values I´m using in my lookup table, thus I have no idea how to solve this.
Could someone help me?
As additional information, my target is to output the number if a second column of the lookuptable based on a clock number which is seek in the first column of the table. I would not mind using a .mat in the table, but I don´t have any idea how to do so.
I would appreacite any hint to solve this.
Don´t hesitate to ask me for more info! thanks in advance
Is it possible to force somehow the indexing service of MS SQL Server 2012 to index a particular filestream/record of a filetable?
If not, is there any way to know if a filestream/record has been indexed?
Thank you very much!
Edit: I found something. I'm not able to index a single file, but I may be able to understand what files have been indexed.
using this query: EXEC sp_fulltext_keymappings #table_id; you'll know every record that has been indexed, is better than nothing...
It sounds like you want to full text index a subset of the files within a single file table. (If it's otherwise, clarify your question and I'll edit the answer). There are two ways you could approach this.
One approach, is to use two distinct FileTables (MyTable_A and MyTable_B), place the files you want indexed in MyTable_A, and the non-indexed ones in MyTable_B. Then apply a full text index to A, but not B. If you need the files to appear in a unified fashion within SQL, just gate access through a view that UNIONs the two filetables. A potential pitfall is that it requires two distinct directory structures. If you need a unified file system structure this approach won't work.
Another approach, is to create an INDEXED VIEW of the files you want to full text indexed. Then apply a full text index to the view. Disclaimer: I have not tried this approach, but apparently it works.
I'm trying to store a lightly filtered copy of a database for offline reference, using ADO.NET DataSets. There are some columns I need not to take with me. So far, it looks like my options are:
Put up with the columns
Get unmaintainably clever about the way I SELECT rows for the DataSet
Hack at the XML output to delete the columns
I've deleted the columns' entries in the DataSet designer. WriteXMl still outputs them, to my dismay. If there's a way to limit WriteXml's output to typed rows, I'd love to hear it.
I tried to filter the columns out with careful SELECT statements, but ended up with a ConstraintException I couldn't solve. Replacing one table's query with SELECT * did the trick. I suspect I could solve the exception given enough time. I also suspect it could come back again as we evolve the schema. I'd prefer not to hand such a maintenance problem to my successors.
All told, I think it'll be easiest to filter the XML output. I need to compress it, store it, and (later) load, decompress, and read it back into a DataSet later. Filtering the XML is only one more step — and, better yet, will only need to happen once a week or so.
Can I change DataSet's behaviour? Should I filter the XML? Is there some fiendishly simple way I can query pretty much, but not quite, everything without running into ConstraintException? Or is my approach entirely wrong? I'd much appreciate your suggestions.
UPDATE: It turns out I copped ConstraintException for a simple reason: I'd forgotten to delete a strongly typed column from one DataTable. It wasn't allowed to be NULL. When I selected all the columns except that column, the value was NULL, and… and, yes, that's profoundly embarrassing, thank you so much for asking.
It's as easy as Table.Columns.Remove("UnwantedColumnName"). I got the lead from
Mehrdad's wonderfully terse answer to another question. I was delighted when Table.Columns turned out to be malleable.